Making Digital Camera Microscope Adapters

Updates: December, 2018.

This page describes the custom adapters and optical engineering assemblies I make to fit a variety of cameras, microscopes, and medical instruments. I engineer and fabricate these adapters personally using my own CAD facility, optical engineering laboratory, machine shop, and electronics workbench. For most of these simpler mechanical adapters, I charge $175 to $375 (USD), depending on the complexity. Adapters incorporating optical elements are more complex and typically cost $500 to $950, including the optics. Complete kits for medical and scientific instruments, with custom mechanical, optical, and electronic components, range from $800 to $6000. Old and new optical instruments are thereby fitted into the modern age of digital imaging. I also research and develop new instrumentation designs for larger projects which involve much higher costs.

Besides the mechanical attachment, these adapters apply one of several optical principles to couple the camera to the microscope, including:

Afocal (through the normal eyepiece to inexpensive small-format digital cameras)

Focal (from a photoport to digital SLR (DSLR) camera bodies)

Focal (from a photoport to small-format digital cameras via a relay lens)

Afocal (through a custom photo-eyepiece for large-lensed digital cameras)

As an example, you can inspect a 3D solid model for a typical adapter [Autodesk DWF file, 26 KB]. (This requires the free Autodesk DWF Viewer). The viewer allows you to rotate ("orbit"), pan and zoom the 3D model so you can see exactly what we are discussing. You can also view the mechanical drawing [PDF file, 30KB].

Here is another 3D model that shows a typical adapter and eyepiece nesting [Autodesk DWF file, 28 KB]. Rotate the model (using the "orbit" tool in the viewer) so you can see how the custom adapter closely fits the supplied microscope eyepiece.

And here is one more 3D model that shows the camera, adapter and eyepiece arrangement. [Autodesk DWF file, 58 KB].

The metalworking process may be illustrated by the first such adapter I made was some years back. This was for a Sony DSC-S30 digital camera, mounting to a Bausch and Lomb microscope. This creates a system for high-quality, wide-field photomicrography.

The lens of the Sony DSC-S30 camera provides a 37 mm inside diameter x 0.75 mm inside threads, and the microscope eyepiece provides a smooth 1.138 inch outer diameter cylinder. Thus the adapter will consist of a turret with outside threads to mate to the camera lens, and an inside bore to slip snugly over the microscope eyepiece.

The first dimensional step is to turn down the cylinder, leaving a raised ridge of 37 mm diameter, ready to take on the outside threads. I chose to thread a length of 5 mm, which was about twice the length of the inside threads on the camera turret. Using the threading bit to turn the smooth diameter makes it easy to leave 60 degree bevels on all the stepped edges. I was happy to find that the 0.75 mm metric thread pitch is available on the minilathe using the standard set of change gears (see the Yahoo 7x10minilathe group files area for tables of using change gears for metric threading). The photos show the work progressing on an aluminum billet I made as a casting experiment, and the casting flaws show up as dark spots or flecks. For later versions, I have been using aerospace grade aluminum stock.

Next I mounted the tailpiece onto the lathe with a drill chuck and 1/2-inch drill bit, and bored a hole into the center of the piece.

With that 0.500 inch starter hole drilled, I was ready to start boring out the 1.138 inch inside diameter that would receive the microscope eyepiece. For this I used carbide boring bar bits that reached the 1" depth of the finished part. (Making the boring bar tool holder is the subject of another of my project descriptions.) After boring the hole a few thousandths oversize, I had a close fit of the adapter to the eyepiece. I finished the part by cutting it from the cylinder using a parting tool. I cut a length that maximized the fitted depth, but still let the camera lens come to rest on the eyepiece. The photo shows the finished adapter.

Below is a view of the Sony DSC-S30 camera, with and without the adapter mounted.

This is an old Bausch and Lomb inspection microscope. This US-manufactured item isn't made any more, but when new they sold for about $2000. The optics are superb, providing a wide, flat field at a variety of zoom magnifications from 7x to 30x. Today, you can find them used on eBay for perhaps $500 or less, or you can buy a similar imported item for about that price new. The turrets of the binocular eyepieces have the virtue of being smooth, even aluminum cylinders. This allows a simple cylindrical adapter to nest on top of the eyepiece.

This is the camera mounted on the microscope eyepiece. The adapter aligns and rigidly fixes the camera to the microscope. The camera lens protrudes in such a way as to touch the eyepiece, so I should apply a bit of vinyl tape as a cushion, or perhaps machine a spacer ring to insert as a standoff. I may add winged setscrews in the future to lock the camera on the eyepiece.

This shows the camera turned on, with the camera display imaging the the microscope's magnified view of a coin. The optical system of this camera is well-matched to the exit pupil of this microscope. By adjusting the camera zoom one can either get a vignetted photo of the full field of the microscope, or a full-framed photo of the center region of the microscope view. Both modes are desirable for various purposes. The photo below shows the full-frame mode.

This is a portion, at full resolution, of a photo taken by the Sony camera in the above setup. The object shown is a Lincoln penny, of which you are seeing part of Lincoln's face. I measured the features shown with calipers, giving a true height of the representation as 0.070 in. The digital image is 526 pixels high. Thus the system resolves about 7500 pixels/inch, which is 7.5 pixels/thousandth-inch, 130 microinches/pixel, or 3.4 microns/pixel. If we assume your display renders 96 pixels/inch, then the effective magnification is about 78x (= 526 pixels / 96 pixels/in / 0.070 in). The camera resolves 1472 x 1104 pixels (not much by today's standards), so the camera and microscope can photograph a physical area of about 0.2 by 0.15 true inches at this level of detail; the full field to the eye view in the microscope is about a 0.25 inch diameter circle. The microscope field zooms from about 1 inch at 7x magnification, to 1/4 inch at 30x. This is an amazing quality of result given that this camera sells for under $200, and the microscope sells used for about $500. Such a system would have cost many $1000s, and required costly film processing, not many years ago. I don't know the resolution limits of the microscope optics, but they're probably better than what the Sony DSC-S30 camera is resolving in this setup. If that is true, then a higher-resolution camera would resolve more detail. I have a much better digital camera now, but it uses a large-aperture lens that isn't as well-matched to the microscope aperture, resulting in a severe vignette in the image. As a general optical design principle, one would want a small camera lens for this kind of behind-the-eyepiece microscopy. With camera lenses, bigger is usually better, since you can gather more light. But digital cameras can (and typically do) have very small, but nevertheless high-quality, lens systems, because the CCD electronic imaging devices are so much smaller than film formats. The light available is determined by the microscope optics, not the camera. Many digital cameras today (2004) seem to be using imaging chips and lenses that are very close to the human eye in physical scale. This is a wonderful thing for those wanting to adapt the cameras to microscopes, because no optical adapters (such as a negative "relay lens") are needed, just mechanical arrangements. The pupil of the human eye may be assume to be about 4 to 5 mm in diameter when viewing microscope images. A good microscope will provide an exit pupil of similar diameter, and the camera lens should match this as well. Not so wonderful for the would-be photomicrographer is the trend away from putting filter mount threads on the lens turrets, even on the more expensive consumer models; later versions of my Sony DSC-S30 have a telescoping lens contraption that regrettably features no thread mount. If you're looking to buy a digital camera with hopes of photomicrography, look for one with a fixed, threaded turret, with the inside thread diameter significantly larger than the microscope eyepiece you hope to use. Even if your camera has an extending/retracting lens turret, you may find an optional adapter tube (see Nikon, Canon, and Olympus examples below) that provides both room for the turret and filter threads for a further adapter. As a last resort, one can fit a sleeve machined just larger than the turret, with one or more screws for clamping to the turret itself.

The original microscopy experiments above were done in 2002. In 2004, I repeated them with the same microscope, but using a higher-resolution camera (Sony DSC-F707, 2560 x 1920 resolution = 5 megapixels) and an Edmund Scientific Co. resolution test target (gratings from 5 lines/mm to 200 lines/mm). This apparatus proved a resolution of 160 lines/mm (4000 lines/inch), or equivalently to 8000 pixels/inch (3 microns/pixel). The photograph shows a contrast enhancement of the 160 lines/mm grating. This is about the same resolution achieved directly viewing into the microscope eyepiece with the naked eye, and is the essential resolution limit imposed by the inspection microscope. Thus a higher-resolution camera does not necessarily translate into higher resolution photomicroscopy images, because the microscope itself introduces the resolution-limiting optical elements. This is a proper approach to the task, where the camera should be chosen to capture an image of some specified area, consistent with the resolution limits and field size of the microscope.

The advantage of a better camera is chiefly the larger field size it can capture at the resolution limits. To the left is a thumbnail of another Lincoln penny image taken with the higher-resolution camera at something less than the maximum magnification. See the full 1600x1600 resolution image here [155 KB JPG file], which makes a 20X image on a typical 96 dpi monitor. We can see a field of up to 0.9 inches diameter at this resolution (2000 pixels/inch), with the whole item imaged at once instead of just the nose. Using combinations of the camera and microscope zoom lenses, the magnification can be increased by another factor of about four to 80X or so, but vignetting will start to reduce the size of the object area.

The Sony DSC-S85 camera with the Sony VAD-S70 adapter (45mm to 52mm lens adapter) provides a 52mm filter thread.

Here are some more digital camera microscope adapters I made for a customer. These slide over a slightly smaller 1.135" eyepiece on a Bausch and Lomb microscope. The smaller item on the left provides an M41x0.5 thread for an Olympus C-3020 digital camera. The larger item on the right provides an M62x0.75 thread for an Olympus E-10 or E-20 digital camera. I used commercial 6061 aluminum round stock for these. The threads on the left look uneven because of an interference pattern (moire effect) on the digital photo. Note the optical illusion which makes the bore look larger on the left adapter compared to the right; they are in fact equal.

The photos below show the attachment of the M41x0.5 adapter (above on left) to an Olympus C-3020 digital camera, and to the microscope eyepiece.

This adapter I made for a customer with a Nikon Coolpix 5700 digital camera (reviewed here and here) and a Nikon Labophot microscope. That Nikon camera is unusual because although it is a rather advanced model, the zoom depends on the lens turret extending various distances in and out of the camera body, like many snapshot cameras. While the lens hood provides a threaded ring, because of the turret extension, you cannot mount a filter or adapter directly to those threads; instead you must use a Nikon UR-E8 adapter (shown in the photos), which is essentially a 34mm long step-down tube from male M53.5-0.75 (mates to lens hood) to female M50x0.75 (for further accessories). This tube has an ID=51mm and OD=55.75mm, with a stop ridge of 47mm ID at 5.5mm inside of the female threads. This is the black item in the photos. The aluminum microscope adapter I made mated to the M50x0.75 thread on the UR-E8 adapter and received a 23mm (OD) Nikon Labophot microscope eyepiece via a slip fit, overall length of 1 inch. After taking these specimen photos, I enlarged the 23mm bore to 29.2mm to slip over the external diameter of the Labophot eyepiece.

Another unusual feature of this adapter is that it can be screwed inside the UR-E8 adapter, or reversibly outside, depending on the camera lens turret extension. This allows the microscope eyepiece a 1.75-inch vertex range relative to the camera, to accommodate various zoom settings while minimizing vignetting. The photos to the left show the reversible mounting.







I made a similar large adapter, with Nylon thumbscrew, to adapt a Nikon D70 digital camera with a 70-300mm zoom lens and 62mm lens thread (M62x0.75), to a Celestron 4060 microscope eyepiece with a 1.100" outside diameter.

This step-down ring adapter (shown in the center of the photo) I made for a customer who already had a Canon LA-DC52C step-up adapter (left of photo) for a Canon A60, A70, A75, or A85 digital camera (similar to the LA-DC52D for the A80 or A95, or the LA-DC52B for the A30 and A40), which provides an M52x0.75 thread, which was to be mounted to a C-mount (1"-32 thread) adapter (right of photo) on the microscope. This Canon adapter, like the Nikon one above, provides an offset tube, inside which the lens turret of the camera has room to extend and retract. Both the inside and outside edges of the ring are threaded, although the photo resolution doesn't resolve all the threads.

This adapter is different than the others in that instead of an unthreaded sliding fit to a cylindrical microscope eyepiece, the adapter provides a female thread to connect to C-mount threads on the microscope. It is essentially a 1/4" thick aluminum washer with threads on the inside and outside edges.

A similar approach would work for the Canon LA-DC58D conversion lens adapter, which provides a 58mm filter thread for the Canon Powershot G6 camera. Likewise for the LA-DC58 for the Powershot G1 and G2, and the LA-DC58B for the Powershot G3 and G5.



This adapter I made for a customer's Olympus C-4000 camera, which provides a 43mm filter thread mount. The smooth inside bore slips closely over the eyepiece (1.162" outside diameter) of a Bausch and Lomb inspection microscope. The height in the photo shows my standard 1-inch overall length for these adapters.

I have also begun including a rubber O-ring with each of the slip-type adapters. For example, for this adapter with a 1.162" inside diameter, a standard inch-series #213 Buna-N O-ring (ID=15/16", OD=1-3/16", section=1/8") fits snugly into the inside diameter without distorting. This provides a cushion against which one can rest the front of the lens turret to achieve a near-minimal vertex distance to the eyepiece optics. To increase the vertex distance, one can insert more of the same O-rings in a stack.

This adapter also required an additional modification (not shown in the photo above or visible in the assembly photo below) to accommodate the turret lens of the camera projecting 0.050" beyond the end of the Olympus CLA-1 41mm-43mm adapter/extension tube for this camera. Since the step ending the 43mm female threads inside the Olympus tube was 0.115" deep, a total length of at least 0.165" (0.2" in practice) had to be relieved inside the threaded end of the adapter, with an inside diameter of 1.575" (40mm) to allow passage of the 1.45" dia extending lens turret.



This photo shows the completed assembly, consisting of the Olympus C-4000 camera, Olympus CLA-1 adapter, and custom microscope adapter.



Most camera filter threads have a tiny 0.75mm spacing ("pitch"). This close-up photo shows a threaded section of the C-4000 adapter above. Threads cut properly on a lathe wiil have a smooth finish and correct profile. Good-quality threads attach easily to the camera lens, and ensure a secure attachment.

I usually design the threaded length to span about 1/4", which is about 8 to 10 fully threaded turns, like you see here. Full engagement to the camera lens typically requires only 2 or 3 careful turns. Should the initial threads of an adapter ever be damaged, such as by dropping it or accidentally cross-threading it into the lens, I can repair it on the lathe by simply facing off a bit of the threaded end, exposing new, undamaged threads at the adapter face.



This custom adapter connects the 37mm filter thread on the customer's camera to an American Optical (AO) inspection microscope 10X eyepiece having a 1.180" outside diameter. This adapter is a bit thin, but still strong enough for the mounting task. In cases where the camera threads happen to be smaller in diameter than the outside of the eyepiece, the adapter uses a shoulder to step up the body diameter and maintain strength.



This photo shows how the eyepiece joins precisely to the adapter with a slip fit. This provides an accurate axial alignment, which minimizes aberrations and distortions in the photo images. By having the customer send the actual eyepiece, a very close fit is guaranteed on the first try.

These slip fits are designed to be close enough for a "telescoping" fit between the eyepiece and the adapter, allowing an adjustable range of vertex distance. The adapter can be fixed on the eyepiece by assembling with a bit of tissue paper or other thin shim for a tight fit. Or, a bit of white glue or cyanoacrylate (CA) glue ("super glue") into the gap creates a semi-permanent attachment; since CA glue does not bond strongly to the oxidized aluminum surfaces of the adapter and eyepiece, the bond is more of a wedge casting than a true glued bond, and the pieces can be later separated and the glue cleaned off if needed. We can also add an optional 1/4"-20 threaded hole and Nylon thumbscrew to the adapter as a clamp.



This custom adapter mounts a Nikon 4500 digital camera with 28mm threads to an Olympus SZ-CTV microscope adapter. The Olympus adapter provides a cylindrical slip fit with a thumbscrew.





This custom adapter mounts a Nikon Coolpix 950 digital camera with 28mm threads to a Leica microscope eyepiece with 1.126" outside diameter. This is an unusual adapter in that the eyepiece diameter exceeds the camera threads, requiring a stepped shoulder on the adapter.





This custom adapter mounts an Olympus C-750 digital camera (via the 55mm Olympus CLA-4 adapter tube) to a cylindrical microscope eyepiece.





These custom adapters are threaded bushings, with C-mount (1"-32) threads on the outside, and 1/4"-20 (UNC coarse) threads on the inside. Lengths are 10mm and 14mm. The cost of a small item like this by weight roughly equates to gold. Precision instrumentation is not cheap.

Here the same two adapters are reworked to 1/2"-20 (UNF fine) inside threads, with a third adapter of 16mm length.



This custom adapter mounts a 37mm camera thread (M37x0.75) to a 1.310" outside diameter cylindrical Bausch & Lomb inspection microscope eyepiece. Note the use of a fitted O-ring as a cushion for the front of the camera lens, which minimizes the reflex distance and vignetting. We provide the correct O-ring(s) as needed with the adapter.





This custom adapter mounts a 30mm camera thread (M30x0.75) to a 1.152" outside diameter cylindrical Bausch & Lomb inspection microscope eyepiece. This mounts a Sony DCR-TRV11 or DCR-TVR27 video camera to the scope.



This custom adapter mounts a 37mm camera thread (M37x0.75) to a 1.221" (31mm) outside diameter cylindrical Nikon CoolPix MDC lens (a relay lens for a Leica MZ16 and other microscopes, also called an MDC-A or MDC-relay, presumably just an acronym for "microscope digital camera" [adapter]). The close-fitting smooth inside bore of the adapter provides a telescoping mechanism which with the single nylon clamping screw (1/4"-20 x 1 inch) provides an adjustable vertex distance between camera and microscope. Male threads (M28x0.75-3mm) at the end of the MDC lens are not used; a fixed step-up ring (28mm to 37mm), a standard item from photographic suppliers, is an alternative for a fixed-vertex-distance adaptation.





The custom adapter (on the right in the photo) is a threaded-flanged bushing which adapts the 28mm (M28x0.75) female thread of the Nikon UR-E6 adapter (on the left in the photo, for a Nikon Coolpix 5000 digital camera) to a female C-mount thread (1"-32) for attachment to a microscope lens. The flange allows one or two O-rings to be inserted to adjust the vertex distance. This bushing weighed only 3.6 grams, and the inside and outside threads cleared each other by a thickness of less than 1mm. The finished item was priced at about 3 times the cost of gold by weight.



This custom adapter mounts a Canon EOS Digital Rebel 300D digital SLR with 18-55 EFS lens (58mm camera thread, M58x0.75) to a 1.154" (29.3mm) outside diamter microscope eyepiece, namely a Leica Mark X Gemolite Stereo Zoom with 15X W.F. eyepieces. The three nylon screws (1/4"-20 x 1-inch) allow for vertex distance adjustment.



Topcon SL-5D and SL-6E Slit Lamp

This custom adapter retrofits Canon and Nikon digital SLRs to the camera port of an ophthalmological instrument, a Topcon slit lamp (Topcon SL-5D slit lamp and Topcon SL-6E slit lamp). The camera port in the original design accepted an obsolete Topcon 35mm film camera back. This photo shows the original bayonet ring mount for the original film camera.

This drawing shows the new adaptation for the Topcon SL-5D and SL-6E slit lamps, consisting of a custom adapter which replaces certain components in the original bayonet mount, and a stock T-mount adapter for the Canon or Nikon digital SLR. The custom adapter provides a male T-mount thread (M42x0.75), on which a commercial adapter (T-mount to EOS) is then attached for the camera. The design works with the original Topcon locking ring to secure the adapter into the instrument. Adapting in two pieces via an intermediate T-mount thread has several benefits: it avoids having to machine the more difficult EOS bayonet lens fitting, it allows rotation of the camera on the instrument, it provides an adjustable vertex distance; and it is compatible with many other T-mount items. The T-mount-to-EOS ring can be purchased inexpensively off-the-shelf, as well as for a wide variety of other camera lens standards. See the detailed mechanical drawing [2.7 MB PDF file] for complete details and specifications.

A photo showing the upgraded camera coupler mounted in a Topcon SL-5E slit lamp, ready to receive the digital camera. The camera coupler locks into the Topcon instrument using the original locking ring and handle seen just below the camera bayonet mount.

A photo showing the Canon 400D (Rebel XTi) digital SLR being mounted on the Topcon SL-5E slit lamp, using the adapter. Close coupling of the new camera to the instrument maintains parfocality with the eyepiece view, while not interfering with the observer's chin. The digital camera can be quickly removed and a conventional lens attached for use in ordinary photography. Besides the Canon 400D (Rebel XTi), the Canon 300D (Digital Rebel), 350D (Digital Rebel XT), 1000D (Digital Rebel XS), and 450D (Digital Rebel XSi) models are also suitable for this application.



Topcon SL-7E and SL-7F Slit Lamps

Shown at left is my digital camera upgrade for the Topcon SL-7E and SL-7F slit lamps. This kit consists of a mechanical bayonet adapter and an electronic interface cable. The assembly is shown here with a Canon 40D digital camera and the original Topcon beamsplitter. The adapter is compatible with all Canon digital SLR models.



The adapter and digital camera are shown here mounted on the beamsplitter for the Topcon SL-7E slit lamp.

See the installation and operating instructions for more diagrams, photos and details.



Nikon FS-2, FS-3, and FS-3V Slit Lamps

Nikon made a series of excellent photo slit lamps up until the early 2000s. These were fitted with beamsplitters and camera attachments for Nikon film SLR bodies. There was also a video camera beamsplitter which is shown in the photo at left. This beamsplitter I adapted for digital SLRs by (1) fabricating a replacement lens cell to change the optical focal length of the adapter to an appropriate magnification for the digital SLR sensor, and (2) fabricating a clamp and fitting for the SLR camera mount.



This is the retrofitted beamsplitter, camera adapter, and digital SLR camera assembled to a Nikon FS-2 slit lamp biomicroscope (without the headrest).



Nikon also made a drop-down type of beamsplitter attachment for the FS-2/FS-3/FS-3V slit lamps, as shown on the left, similar in principle to the Topcon SL-7E and SL-7F slit lamps. The Nikon beamsplitter provided a solenoid-operated mirror and electronic interface for film photography on the slit lamp. The mirror flip provided 100 percent light to the eyepieces during the examination, while redirecting the same light to the camera during the moment of photographic exposure. This avoids losing light in the 50/50 or 70/30 division in the usual prismatic or half-mirror beamsplitter. I have seen these beamsplitters in four various configurations for different camera body types: (1) with a standard Nikon F bayonet, and hard-wired cables providing the standard Nikon remote shutter connector (10-pin round) and standard PC flash-sync connector; (2) also with Nikon F bayonet but an 8-pin Hirose RP6 receptacle connector (no longer made) for the shutter and flash sync signals; (3) like the previous but with a 10-pin Hirose RP6 connector; and (4) with an unusual Nikon bayonet mount (which is not the Nikon F mount) for scientific instrumentation having pogo-pin connections, similar to what is used on the Topcon TRC-50EX and TRC-50DX retinal cameras (for which Nikon apparently made the 35mm film camera bodies). The first beamsplitter configuration with its Nikon-F bayonet can accept a Nikon digital SLR without modification, if the digital SLR model is one of the mid-range or high-end models that provide the 10-pin type of connector. To use other Nikon digital SLR models providing different remote connectors requires splicing in the appropriate connector. The bayonet on the second and third beamsplitter configuration also fits a Nikon digital SLR directly, but the electronics must be disassembled and modified to replace the obsolete Hirose connection with cables and signals to fit the DSLR shutter and flash sync interfaces. The fourth beamsplitter configuration requires both mechanical and electronic adaptations such as shown on the left, where I replaced the instrumentation bayonet with a custom T-mount lens fitting, and I added an electronic interface and cabling for shutter remote and flash sync, such as for the Nikon D7000 shown. The T-mount adaptation can also be applied to the Nikon F configuration to allow use with Canon and other non-Nikon digital SLRs via hot-shoe connector.



Here is the retrofitted beamsplitter and custom camera adapter assembled to a Nikon FS-3V slit lamp biomicroscope (without the headrest, illumination tower, and flash power supply), shown with a Nikon D7000 DSLR for digital photography. Nikon used infinity-optics and stackable-dovetail-accessory principles as introduced by Zeiss. This is a superb instrument with built-in flash for slit-lamp photography of the highest quality, originally in the film era but now in digital technology. In my opinion the zoom optics and integrated flash make this the best photographic slit lamp ever made, rivalled only by the current Haag-Streit BX900. Too bad Nikon did not succeed in this business, and discontinued making slit lamps and retinal cameras in the early 2000s. The $20K price in those days was extremely costly for a clinical instrument, which explains why this could not have been a big seller and is rarely found now.

If you are fortunate to own one of these fine Nikon instruments with a film camera, please contact me to retrofit it to digital photography and preserve its value and enduring worth.



Topcon TRC-50EX and TRC-50X Retinal Cameras (Upper Port Digital Camera Adapter)

This is an updated version of the upper-port adapter for the Topcon TRC-50EX retinal camera. For more photos and technical details, see the installation and operating instructions. You can also read the original TRC-50EX instruction manual [4 MB PDF file, 71 pages]. I also make a Topcon TRC-50X digital adapter (technical details and ordering); you can also download the original TRC-50X instruction manual [6 MB PDF file, 46 pages]. See a sample digital retinal photo [1.2 MB JPEG image] taken on a Topcon TRC-50X with a Canon T2i digital SLR camera using this adapter.



This adapter couples a Topcon TRC-50EX retinal camera to a Canon 400D digital SLR. It is complex, consisting of optical, mechanical, and electrical components. See the installation and operating instructions for more diagrams, photos and details. Five optical elements in two groups resize and relocate the instrument exit pupil at a suitable distance for a relay lens, which in turn refocuses the image at a size to match the camera's digital sensor, which is 0.6 the size of the original 35mm film intended for the instrument. Mechanical components maintain a rigid positioning of the optics, as well as axial and rotational adjustments for focusing and alignment. The electronic interface cable (not shown) operates the digital camera synchronously with the instrument triggers.



This photo shows the adapter mounted on a Canon 400D digital SLR camera. Besides the 5 optical elements, the adapter consists of 4 custom and 2 stock mechanical assemblies.



Here's the adapter and camera mounted on the Topcon TRC-50EX. We have used the upper port which the Topcon TRC-50EX provides for mounting an accessory camera. To take a photo, the operator pushes a button on the instrument joystick to trigger a synchronized series of events: First, an instrument mirror flips to redirect the image from the viewfinder eyepiece to the upper camera. Second, the instrument sends an electronic signal to the digital camera to open the its shutter. Third, when the digital camera has opened its shutter, it returns an electronic signal to the instrument to fire the flash illumination. Fourth, the instrument fires the flash. Fifth, the camera shutter closes. Finally, the instrument returns the mirror to the viewfinder path. The custom cable which connects the digital SLR's shutter release and flash sync to the Topcon instrument is not shown here.



Topcon TRC-50EX Retinal Camera (Rear Port Digital Camera Adapter)

A later design of mine shown here for the Topcon TRC-50EX rear port is a bayonet adapter with gold "pogo pin" connection (also called a "hot shoe" connection) for electronic interface to the Topcon instrument. The pins and housing for the electronic interface are a custom, precision design and assembly fitted to match the original dimensions. One side provides the mechanical Canon bayonet attachment, and the other the Topcon bayonet. See the mechanical drawing [572 KB PDF file, 1 page] for details. This adapter also fits the latest Topcon TRC-50DX retinal cameras, which use the same rear port interface, but an extension on the port is required, with a matching extension inserted in the viewfinder, to avoid interference between the digital camera body and the case on the TRC-50DX (which unfortunately projects out further than on the TRC-50EX).



This adapter works with the full-frame Canon 5D Mark II digital SLR to replace the Topcon MT-10 film camera which originally took photographs on the instrument. The adapter provides an attachment at a parfocal distance so that the digital camera is mechanically and optically equal to the film camera being replaced. Parfocality in this adapter is crucial, since the instrument's original eyepiece viewfinder is retained. The required distances leave only a few millimeters of space within which to machine both the bayonet mechanisms and the electronics assembly.



This photo shows the digital camera mounted on the instrument with the adapter. The instrument joystick triggers the digital camera shutter via the Canon remote connector, and the Canon flash sync terminal in turn fires the Topcon instrument flash. Photos are immediately reviewable on the camera as shown, or may be automatically transferred and displayed on an attached PC via tethering software.



To provide parfocality, mounting of the digital camera must be very close to the instrument. The Canon 5D digital SLR body just barely clears any interference with the Topcon exterior. Other brands and models of digital camera bodies will not fit here, because they have features such as a built-in flash which project too far forward and would not permit this close adaptation.



The camera is mounted upside down to avoid mechanical interference with the original viewfinder, and to yield an upright image from the Topcon instrumentation optics, which are inverted relative to an ordinary SLR camera lens..

The adapter works with both the Canon 5D and the Canon 5D Mark II model camera bodies. The digital camera readily detaches and is then usable for ordinary photography by attaching a conventional SLR lens, or to switch to a different instrument.

See also the installation instructions for this product.



Kowa fx-50R Retinal Camera (Rear Port Digital Camera Adapter)

This adapter, seen on the lower port of a Kowa fx-50R retinal camera where a Polaroid camera used to attach, fits a Canon digital camera with a macro lens to the instrument. The smaller original 35mm film camera body is seen on the rear port, above which is the viewfinding eyepiece. Kowa's instrument design is quite suitable for digital conversion because the viewfinder is a fixed and separate part of the instrument, instead of being incorporated into the 35mm film or Polaroid film camera backs.

The diagonal mirror on the digital adapter orients the camera to clear of the rest of the instrument, and unmirrors the image which was previously mirrored inside the instrument. A single lens element in the adapter acts as a field lens to avoid vignetting in the macro imaging technique. A custom electronic cable inserts between the original connectors to intercept the joystick pushbutton signal, remotely triggering the digital camera shutter instead of the instrument; the cable also forwards the digital camera flash sync signal to the instrument to triggers the instrument flash.

The adapter provides two swivel adjustment mechanisms, one on each side of the diagonal, with setscrews and thumbscrews for adjustment and locking. This permits the adapter to pivot to the operator's right or left while still producing an upright digital image. This left or right pivot moves the digital camera out of the photographer's way, although it is not then so convenient for reviewing photos on the camera's display. Tethering the camera to a PC display is thus desirable with the pivoted orientations.

This adapter also fits the newer Kowa fx-500 (Kowa fx-500S) retinal cameras.

Technical details and more photos are available in the installation and use instructions.



Kowa RC-2 Handheld Retinal Camera (Rear Port Digital Camera Adapter)

This adapter converts an unusual retinal camera, which is portable and handheld, for digital photography. The instrument provides a steady illumination lamp for examination of the patient's retina as well as a xenon flash lamp for photography. Light from these lamps exits the prism, just under the objective lens, where it enters the pupil of the subject eye at a steep angle to avoid a corneal reflection back towards the observer's point of view. The original compact camera body used 35mm film in direct projection and was attached with a locking rail mechanism. The film camera also provided a reflex viewfinder. To adapt this instrument for digital photography, we first remove the film camera and replace it with a custom-machined threaded bushing that fits around the exit lens and is attached with screws in place of those that held the rails. Then onto this thread we can attach a 3-part adapter consisting of a 30mm eyepiece barrel, eyepiece adapter, and stock conversion lens adapter tube. A 30mm wide-field eyepiece with 22mm field number is chosen to afocalize the image for a Canon G10 (or G11 or G12) digital camera, which provides the full field of view of the original instrument. The eyepiece also provides a very long exit pupil that reaches into the very deep entrance pupil of the Canon lens on this type of camera. White Nylon setscrews provide rotational calibration of the camera orientation, and axial alignment of the camera entrance pupil.



Viewfinding is now done digitally on the LCD screen of the camera. We used the Canon G10 (or G11 or G12) camera rather than a digital SLR because of the weight requirements of the handheld design, and the mechanical interference that parfocal mounting of an SLR would have imposed. The adapter components are all aluminum or Delrin for minimal weight.

Part of the economy of the original design was to route the 300 volt xenon flash trigger through the film camera, which must now be isolated from the digital camera electronics. A "safe sync" adapter connects the flash synchronization signal from the Canon camera to the high-voltage PC-sync connector on the instrument.

Haag-Streit BM 900 Slit Lamp Digital Camera Adapter

This device adapts a Canon digital SLR (or other T-mount adaptable SLR body) to the eyetube of a Haag-Streit BM 900 slit lamp, providing digital photography through this 50-year-old classic instrument design. The eyepieces of this instrument are of an older Huygenian design no longer used much for microscopy, requiring an unusual adapter geometry. The barrel diameter and flange distance of this Haag-Streit model are also non-standard, requiring customization of the adapter tube. A telescoping lens cell with thumbscrew lock allows for parfocal calibration to the instrument's focal plane with inscribed crop of the full field of view, or the crop factor can be adjusted with consequent non-parfocal operation. The adapter body is machined from black Delrin; the narrow barrel is machined from aluminum with flat black paint inside.



Here is the Haag-Streit BM 900 adapter mounted on a Canon 40D digital SLR camera. To take a photograph, the examiner replaces one of the eyepieces with the adapted camera. Framing and focusing are available through the other binocular eyepiece, or through the viewfinder of the digital camera. An optional foot switch provide hands-free shutter operation. The design is based on the T-mount thread mount, which through an inexpensive bayonet component allows use with any make or model of digital SLR camera.



Topcon TRC-NW6 Non-Mydriatic Retinal Camera Digital Adapter

This adapter upgrades a Topcon non-mydriatic retinal camera to use a Canon digital SLR camera instead of the Polaroid or 35mm film camera originally fitted. The electrical interface uses an interpolation technique, whereby the internal circuitry is modified to intercept the joystick trigger signal and send it through the digital camera before processing by the instrument, thus synchronizing the otherwise incompatible timing.



This adapter requires much in the way of precise mechanical improvisation since the instrument uses two simultaneous connections for electrical versus mechanical connection, as opposed to earlier Topcon models which tended to incorporate them into one connection. The optical design exploits the macro principle available on certain Canon lenses, which fills the digital frame with the instrument image while permitting parfocal calibration to the infrared imaging system of the non-mydriatic viewfinder.



More photos and technical details are found in the installation and operating instructions for the Topcon TRC-NW6 digital adapter here.

See a sample retinal image [2269 x 2269 pixels, JPEG 1.4MB] taken with the Topcon TRC-NW6 using the adapter with a Canon 40D digital camera.

Topcon TRC-NW3 Non-Mydriatic Retinal Camera

This custom-modified attachment for the Topcon TRC-NW3 retinal camera upgrades the system for digital photography. This Topcon model is older than the Topcon TRC-NW6 above, but performs very well and is an excellent base for a digitally upgraded system. See the Topcon TRC-NW3 digital upgrade instruction manual for more technical details and photos. You can also read the original Topcon TRC-NW3 instruction manual [6 MB PDF file, 31 pages].



Topcon TRC-50VT Retinal Camera

This adapter kit converts a Topcon TRC-50VT retinal camera (also known as a fundus camera) from the original film camera back to use a Canon EOS digital SLR camera. The kit consists of:

A mechanical adapter to mount the Canon digital camera on the Topcon instrument in a precisely parfocal, axially centered position.

A modified breech ring that replaces the original Topcon ring, which avoids the mechanical interference of the flash "nose" of certain Canon SLR models with the instrument.

An neutral-density filter for the Topcon instrument, which reduces the instrument's flash intensity to compensate for the Canon digital SLR's improved light sensitivity.

A flash synchronization adapter cable, which triggers the Topcon instrument flash in synchronization with the Canon digital camera shutter. This cable adapts the Canon digital camera flash trigger signal to the DB-15 connector provided on the Topcon TRC-50VT, which was originally intended for a Polaroid camera.

See the mechanical drawing [700 KB PDF file] for a detailed view of the adapted camera mounting.



There are 3 options I build for the Topcon TRC-50VT:

Direct projection to an APS-frame Canon or Nikon digital SLR, such as the Canon 50D, Direct projection to a full-frame Canon 5D or 5D Mark II on the rear port, and Relay lens to a APS-frame Canon or Nikon digital SLR on the upper port.

Option (1) imposes an 0.6X crop factor, so you lose some of the top and bottom of the image, both in viewing and in imaging. Options (2) and (3) don't crop, they show the full frame.

Options (1) and (2) mount the digital camera on the rear port, close to the instrument like the original film camera. Option (3) mounts the digital camera above the top of the instrument on the upper port, similar to the optional Polaroid or TV attachments Topcon originally sold for the instrument.

Options (1) and (2) show an inverted preview, which you either get used to, or use my inverting Canon viewfinder magnifier, which adds 4 inches of length the rear of the camera. These options also eliminate the Topcon viewfinder as a consequence of using the rear port. The Canon viewfinder is a focusing-screen type with a beamsplitter for autofocus and exposure metering, which is necessarily smaller and less bright compared to the original Topcon viewfinder eyepiece with its near-100 percent transmission. You typically have to boost the steady illumination to compensate with difficult subject eyes compared to the Topcon film camera viewfinder, which adds another difficulty factor in itself to marginally viewable subjects. Viewfinding for fluorescein angiography (FA) is thus hardly possible, since the views are so dim even in the Topcon viewfinder.

Option (3) retains the Topcon film camera for viewfinding, with the digital camera acting as an image recorder only. This configuration performs with the same superb clinical convenience of the original design. The chief disadvantage is the higher cost. A secondary disadvantage is that it relies on the mirror-flip mechanism for the upper port, which has proven trouble-prone in the aging Topcon film-based instruments.

The complete adaptation requires not only mechanical and optical devices, but an electronic interface as well, since the old film cameras used a different signaling and synchronization method than today's digital cameras. At left is a photo of the joystick interpolation connector I designed for this pupose, consisting of a custom machined housing holding the appropriate connectors and containing an electronic chip and wiring.. This device inserts between the plug and socket connecting the Topcon joystick to the Topcon controller, and provides a new cable to the digital camera shutter remote connector. This allows the digital camera to shoot a picture whenever the joystick button is pressed. The camera remote connector shown is for a Canon N3 type; Canon E3 or Nikon 10-pin connectors are also supported by the design. Flash synchronization of the instrument to the digital camera is provided by a separate electronic interface using a similar arrangement. For more details, see the installation instructions for the interpolation cable.



Other model Canon cameras such as the Digital Rebel series (original, XT, XTi, XS, and XSi models, also known as the 300D, 350D, 400D, 1000D, and 450D respectively), and the 10D/20D/30D/40D/50D series, are compatible with options (1) and (3).

This adapter converts the rear port of the Topcon TRC-50VT retinal camera to the C-mount interface such as for attaching a video camera. The front of the adapter is the bayonet used in the Topcon instrumentation; the rear is a standard C-mount thread. The length is chosen to make the C-mount attachment parfocal with the original film camera. The assembly also provides a dovetail adjustment with setscrews to rotate the attached device into alignment with the Topcon instrument. This is for specialized applications of the instrument, since the C-mount format will crop the 22mm diameter instrument image circle to about 18mm or less.



For further details on this instrument, see the original Topcon TRC-50VT instruction manual [91 MB PDF file, 46 pages]. To disassemble the complete Topcon TRC-50VT into smaller pieces for parcel shipping, see my instructions. See also the diagnostic test set for the Topcon TRC-50VT which I designed and built to diagnose problems with the interface between the Topcon instrument and the Canon digital cameras.

Canon CR6-45NM Non-Mydriatic Retinal Camera

Shown at left is my digital camera upgrade for the Canon CR6-45NM retinal camera. I build this adapter starting with the original bayonet receptacle from the Polaroid camera which was used on this instrument. To this I add (1) a mechanical adapter, (2) an electronic interface with cables to the digital camera shutter and flash sync, (3) a stock Canon lens, and (4) a neutral density filter to reduce the flash intensity for the digital exposure. The assembly is shown here with a Canon Digital Rebel XTi SLR camera body and Canon 28mm lens. The adapter is compatible with all Canon digital SLR models.



The adapter and digital camera are shown here mounted on the Canon CR6-45NM retinal camera. The process of taking a non-mydriatic retinal photo is identical to the 35mm film or Polaroid photography originally employed on this unit.

See the installation and operating instructions for more diagrams, photos and details.

See the Canon CR-DA1 operation manual for details of a digital camera adapter Canon made for the Canon CR6-45NM.



Canon CR4-45NM Non-Mydriatic Retinal Camera

This is a digital camera upgrade for the Canon CR4-45NM retinal camera. This Canon model is older than the Canon CR6-45NM above, but performs very well and is an excellent base for a digitally upgraded system. See the installation and operating instructions for more diagrams, photos and details.



Canon CF-60U and CF-60ZA Retinal Cameras

The Canon CF-60U retinal camera originally used the Canon F-A 35mm film camera body, which was a special model of the popular Canon F 35mm film camera. Upgrading this instrument to digital requires that the old "pogo pin" connector to the film camera be removed and replaced with a standard connector and electronic interface circuit which connects the instrument joystick and flash synchronization to the digital camera. Shown here is the rear port area with this connector upgrade installed. Installing this upgraded connector involves disassembling the upper unit, and then cutting and soldering the internal wiring. This in turn requires either sending the upper unit to me, or using the services of an on-site electronics technician following my documented instructions.



After the electronic connector is installed, a full-frame Canon 5D Mark II digital SLR is mechanically adapted to the rear port bayonet fitting of the instrument. A digital camera attached via an ordinary adapter ring is not parfocal with the original film camera operation, the focal plane of the digital camera being several mm further back than the film camera's. Thus a modified bayonet attachment assembly (not shown) replaces the original on the back of the instrument, to allow parfocal attachment of the digital camera. Not shown here is the electronic interface cable (see next photo).



These are the individual components for the electronic interface to digitally upgrade the Canon CF-60U retinal camera. The bracket is a custom-machined piece to replace the original "pogo pin" assembly that connected the instrument to the old film camera. The connector receptacle (not shown, see above photos) mounts in the large hole in the bracket, and connects to the mating plug on the cable. . The cable connects the digital camera, splitting into two connectors, one for the Canon shutter remote and another for the Canon hot-shoe flash synchronization. An electronic interface circuit contained inside the grey connector hood converts the logic and levels of the film camera signals to be compatible with the digital connections.



Olympus ENF Type P3 Endoscope to Canon SD750 Camera

About the application: A modern medical endoscope is an instrument to illuminate and examine deep within a narrow channel through a thin fiber optic imaging bundle. Typically this image is presented to the examiner through an eyepiece with a very narrow field of view. The examiner may view the image directly by looking into the eyepiece, or on an attached display, typically made to the eyepiece through a C-mount relay lens adapter to a video camera. Attachment to current digital cameras is feasible but not supported by the medical endoscope manufacturers. This project sought to attach a digital camera to an Olympus ENF Type P3 endoscope to provide both a live digital video display and recording for teaching, and high-resolution still digital photography.

Why adapt an un-adaptable camera? Important to the endoscope user is the light weight of the instrument and attachments, which must be held and manipulated in one hand during an examination. This suggests the use of the high-quality but ultra-compact digital cameras such as the Canon SD series (Canon SD750, Canon SD790). It is a frustratingly universal lack of compact digital cameras of all makes that they provide no means to attach lens accessories, and are therefore not mechanically adaptable to instrumentation, although they are quite suitable optically. For this reason I developed a flanged-threaded adapter tube, shown in this photo, for securely attaching accessories to the Canon SD cameras. This tube provides a 30mm (M30x0.75) internal thread for attaching accessories, while allowing for the free movement and extension of the camera lens turret.



The adapter tube for Canon SD cameras: The adapter tube attaches permanently to the camera body as shown in the two views of this photo. On the left is the original camera with the lens turret extended. On the right is the camera as modified by the attachment of the adapter. This requires disassembling and separating the front metal cover from the camera, gently removing the decorative bezel (held on by contact adhesive) from around the camera lens passage of the cover, drilling three precisely placed miniature holes around the lens passage in the cover, attaching the adapter to the cover with three miniature screws, and reassembling the camera. This modification is thus not a user-installable item, requiring modification at the machine shop here, with careful technique to avoid damaging the fragile internal camera mechanisms. The adapter piece is machined from aluminum to be very lightweight yet strong. It will fit many of the SD models, namely all the Canon SD7xx series which use this case design. The success of this adaptation depends on (1) the easy disassembly of the front cover, (2) the cover being made of sturdy metal and not plastic, and (3) there being some clearance behind the cover at the critical points where the newly added screw heads project back. The design would work on other Canon compact models, or other brands of compact cameras, which have these cover characteristics.

Reversible, non-interfering design: The notch in the flange of the adapter provides clearance to the built-in camera flash, which otherwise would be partly obscured. Two additional holes in the flange provide passages through the adapter for features on the front of the camera, namely the focus-assist lamp and the microphone. While the endoscope does not use these camera features, the adapter is designed to not interfere with the normal operation of the camera when off the endoscope. The only difference from normal operation is that normally the lens turret retracts when the power is off, making the camera more compact, while on the modified camera the adapter is always projecting. The modification may be reversed by disassembling the cover again and removing the miniature screws holding on the adapter. Replacing the decorative bezel then hides the holes added to the front cover.

Optical compatibility: The Canon SD series cameras, and indeed just about all compact cameras, have a lens and iris smaller in scale than the human eye, which means that they will couple directly to just about any eyepiece or other instrument designed for eye viewing. The modification to accept attachments thus converts the camera into something very versatile for instrumentation applications. One could only wish that the original camera came with an attachment provision. Advancing technology and economy have made these cameras cost less than this custom modification work.

Endoscope eyepiece optics: A consideration with fiber endoscopes is the narrow presentation in the eyepiece view. The apparent size of the circular field of view in an endoscope eyepiece is typically only 7 degrees, versus about 40 or 45 degrees in a typical wide-field microscope eyepiece. Indeed, when first using an endoscope, the observer tends to feel as though the instrument is not properly designed, since the image is so small compared to what one is used to in other optical instruments such as a compound microscope. But the narrow view and low magnification is in fact a sound design. Since the fiber bundle represents only a few hundred pixels across, comparable to the resolution of the observer's eye over a similar angle, magnifying the image further would not improve the visual resolution. Since minimal lighting is desirable in endoscopy to minimize heating of tissues, and image brightness is increased by lower eyepiece magnification, the eyepiece design is chosen for the minimal magnification that will just allow an acute eye to resolve the individual fibers or a little better. While this is all suitable for visual use, the attachment of a camera presents a challenge, lest the useful image crop to the narrow center of the camera field of view, leaving most of the field unused. When attaching an afocal camera with a simple mechanical adapter, the camera must be capable of an almost telescopic zoom to enlarge a 7 degree subject enough to fill the camera field of view, equivalent to a 200mm lens on a 35mm film camera. Otherwise the endoscope image will never be larger than a small circle in a larger black camera field. A typical point-and-shoot camera might have an optical zoom range of 4:1, with the lens being equivalent to a 28mm to 112mm zoom lens in a 35mm film camera, corresponding to an angle of view from 45 degrees (wide angle) to 12 degrees (telephoto) in the vertical aspect. Such a camera at maximum telephoto zoom will not fill the photograph's vertical aspect with optical zoom only, requiring that a small extra digital zoom be applied. Since the camera's megapixels of resolution far out-resolve the kilopixels of effective endoscope fiber resolution, the slight application of digital zoom does not limit the resolution of the overall system. At the same time, applying maximum telephoto zoom in the camera lens will retract the camera's entrance pupil maximally away from the front vertex of the lens assembly, so the exit pupil of the endoscope eyepiece must still be able to reach the entrance pupil within the constraints imposed by the mechanical coupling. But happily, all these optical and mechanical issues resolve into a good fit with the Canon SD series and Nikon L series of compact cameras.

Endoscope eyepieces tend to have an extra generous eye relief, by virtue of the fact that the fiber bundle, which is the aperture stop of the system, is very close to the eyepiece lens. The exit pupil, being the image of this aperture stop as imaged by the eyepiece, can thus be 25mm or more above the end of the eyepiece, so the reach into a compact telephoto lens is typically feasible. Contrast this with a compound microscope which, although having a similar eyepiece, has an aperture stop imposed by the microscope objective which is 160mm or more from the eyepiece, placing the exit pupil only about 16mm above the end of the eyepiece, and not able to reach the entrance pupil of a zoomed camera lens.



The endoscope adapter: A second custom adapter piece attaches the modified Canon SD750 camera to the endoscope's standard mushroom eyepiece, also known as the endoscope "B-cup" eyepiece. A 30mm thread attaches to the threads of the modified Canon SD750, and a bushing with three Nylon thumbscrews attaches to the endoscope. This piece is machined from polyacetal engineering polymer (Delrin). A larger thread size or a step-down ring would make this adapter compatible with other cameras with filter threads already on the lens, or that accept conversion lens adapter tubes with filter threads. More complex (but more convenient) clamping systems are typically used on older stock adapters for these instruments, but these are not feasible to produce in a custom shop.





The assembly: This photo shows the arrangement of the Olympus endoscope to the modified Canon camera and custom adapter. The endoscope provides a standard mushroom-shaped end ("B-cup") to the eyepiece. This shape allows for direct viewing by eye, or for the mechanical attachment of accessories.



Here we see the completed assembly. The thumbscrews allow for rapid attachment, rotational alignment, and detachment of the adapted camera. The attachment is firm and definite, yet the Nylon thumbscrew tips will not mar the hard eyepiece body. Endoscope eyepieces typically provide a very narrow field of view, so setting about a 5X telephoto zoom on the Canon SD750 fills the camera field of view with the endoscopic view in an inscribed crop. By using the camera zoom, we eliminate the need for any costly beam-expanding optics in the adapter. The potential Moire effect due to the digital pixels sampling the discrete fibers of the image is nulled out by adjusting the rotation of the camera on the endoscope, and by the high resolution of the camera oversampling the fiber ends. The nearly telecentric exit pupil of the endoscope eyepiece makes this type of adaptation possible with virtually any camera lens with sufficient zoom. The fiber optics of the endoscope are limited to some hundreds of elements in each dimension, equivalent to about 1 megapixel of image sampling, so the digital camera's many megapixels of resolution are more than adequate for a full rendition of the instrument's capabilities.



This is the endoscope adapter updated for the more recent Canon SD1300 compact camera. Canon changes camera models frequently, requiring frequent adjustments to the adapter designs.



This is the endoscope adapter updated for the more recent Canon ELPH 310HS compact camera, shown with a Storz 11101RP2 endoscope. This Storz model provides a standard B-cup eyepiece like the Olympus P3 endoscope above. This Canon camera provides a digital teleconverter and 8X optical zoom which allows coupling to the difficult field of view requirements and eye relief of the endoscope, without additional optics. This adaptation requires I sell the new camera itself (see ordering page), modified with the adapter installed, since the only feasible attachment method requires the delicate disassembly and modification of the original shell of the camera.



Digital SLR Camera Adapter for Zeiss OPMI instruments (slit lamps and operating microscopes) with Zeiss beamsplitter

The adapter shown in the photo adapts a digital SLR camera on the left to a Zeiss OPMI beamsplitter on the right, The Zeiss OPMI (operating microscope) system is an infinity-optics design (sometimes called "parallel optics", which is not quite proper) which allows for the insertion of the beamsplitter shown into the stacked instrument components using a dovetail and dovetail-receptacle mechanism. This same OPMI dovetail interface is used on Zeiss operating microscopes as well as Zeiss slit lamps, and the digital camera adapter is compatible with any Zeiss OPMI instrument accessory fitting (see the drawing with details of this fitting). The custom adapter allows the use of any digital SLR camera via a T-mount mechanical interface, for which a Pentax K10D digital SLR is shown here.



Here is the adapter and beamsplitter assembled with a Canon 40D digital SLR camera. A screw-and-lockring feature on the adapter allows for parfocal calibration of the camera to the binocular eyepiece view of the Zeiss instrument. Parfocal calibration permits shooting precisely focused digital pictures using the normal instrument view, instead of having to focus through the camera viewfinder.

Optically, this is an afocal-focal adapter design, which incorporates a multielement lens to focalize the infinity image at the proper position and scale for the digital camera sensor, taking into account the Zeiss instrument's aperture stops and mechanical constraints. The Zeiss attachment mechanism at the beamsplitter is an unusual threaded locking-tab type.

Photographic lighting using the normal slit illuminator is sufficient if the digital camera is set to a high ISO sensitivity. Thus the full range of slit lamp diagnostic examination may be photographed. Another convenient feature of this adaptation is that the built-in flash of the digital camera can be raised, and diffused and reflected with a white card, to take low-magnification, high-resolution photos of the entire eye.

The grub-screw feature of the T-mount adapter provides rotational alignment of the camera in any desired orientation. The Zeiss OPMI beamsplitter provides two ports, one for each of the two stereoscopic binocular views, and the adapted camera may be mounted on either side. Two digital cameras and adapters, one on each side of a single beamsplitter, would provide stereoscopic pair photography!



Here is the adapted camera and beamsplitter assembled with a Zeiss slit lamp. The adapter and camera are lightweight and do not interfere with the smooth motion and stability of the microscopic examination. Part of this economy is to omit a 90-degree mirror from the adapter, which results in mirrored photographs, which are then unmirrored later in software. A separate adapter cable (not shown) connects the digital camera remote shutter to the Zeiss slit lamp joystick button, allowing the examiner to use one hand to manipulate the instrument into position and focus, and shoot digital photos, while leaving the other hand free to assist the patient. We've also made footswitch shutter releases for practitioners favoring a "third hand" option.

See also a high-resolution (3872 x 2592) digital anterior photograph [513KB JPEG file] as taken with this instrument and adapter.



The larger design at the left adds a precision diagonal mirror fitting via an "elbow" component to the Zeiss OPMI adapter. Unlike the simpler straight-tube design above, this produces unmirrored images in the digital camera. The T-mount exit fitting adapts easily to Canon, Nikon, or other digital SLR cameras. A telescoping mechanism with thumbscrew lock provides both parfocal calibration to the instrument and various orientations to suit the desired clearance around the instrument. Compare my design to an original Zeiss f=137 video camera adapter (manufactured for Zeiss by Urban Engineering in the US) from many years ago and no longer available, seen in this photo 1 and photo 2.

The Zeiss item provided a manually adjustable iris to set the optical aperture from f/8 to f/44, which trades off the light available for exposure with the depth of field in focus. In my DSLR adapter this aperture feature is available by assembling an optional, non-adjustable aperture-stop disk which I fabricate for any desired f/number next to the lens.



Here is the elbow adapter shown with a Zeiss beamsplitter as used with Zeiss SL-120 and SL-130 slit lamps. These Zeiss models use a slightly modified dovetail instrument interface that is not quite compatible with the classic Zeiss OPMI instruments, but the beamsplitter still provides the same OPMI accessory interface on the exit attachment point. The digital SLR shown here is a Canon 40D; all Canon SLR models are compatible.



Here is the elbow adapter, Zeiss OPMI beamsplitter, and digital SLR shown on a Zeiss 125/16 slit lamp.



This is my adapter for a Global (brand) operating (surgical or dental) microscope, with attaches a LoupeCam miniature HD camera to the microscope beamsplitter. Global surgical microscopes are similar in optical principle to the Zeiss OPMI instruments, but with slightly different (and incompatible) mechanical fittings, such that attachments and adapters for one will not work with the other. The assembly is very small; the diameter of the camera body shown is a little less than an inch in diameter. This camera provides a USB connection for live HD video and high-resolution still photography. See additional photos from the Global-LoupeCam adapter here.



This is another adapter for the Global operating microscope, which is a modification of an existing Global adapter which originally used a now-obsolete Panasonic GP-KS162HD "lipstick" camera. I retrofitted the original Global adapter to provide a standard C-mount camera fitting, and shortened the length to match the focal plane to the C-mount optical requirements. Thus the adapter can now work with any standard industrial/scientific camera rather than depending on one make-and-model like the original design. This result is shown here with an Edmund Optics EO-1312C HD color camera, which provides a USB 3.0 connection to a computer for high-resolution stills and HD live video. The cost for this modification work is only a fifth of the price of a new adapter with similar capabilities. See the detailed instructions for installing this adapter.



These Zeiss operating microscope digital camera attachments can be used on classic Leica instruments such as the Leica 690 operating microscopes via an Zeiss-Leica adapter. See the drawing (1-page PDF file).

This attachment provides live imaging of microscopic surgical fields with tunable color filtering. This assembly combines my Zeiss OPMI adapter with custom fittings to a CRi Varispec LCTF (liquid crystal tunable filter, model VIS-07-HC-20, which is the blue box), ending in another custom adapter to an Apogee high-sensitivity camera with D02 (2"-24) thread mount. An alternate back end provides compatibility with C-mount cameras. The camera adapter assembly consists (1) a custom fitting with f=125mm f/5.2 objective lens for the Zeiss OPMI accessory port, (2) a Thorlabs CRM1/M cage rotation mount with polarizer element, (3) a custom adapter from the previous components to the Varispec LCTF dovetail fitting, (4) a custom adapter from the LCTF dovetail to Apogee camera 2"-24 thread, providing a focusing adjustment. A second version of (4) consists of a custom adapter from the LCTF dovetail to a C-mount camera, incorporating an second lens (f=50mm) to reduce the combined effective focal length to f=75mm f/3.1 for cropping to a smaller format. A third version of (4) consists of an eyepiece adapter for direct visual observation. The focal lengths and apertures of the optical system are chosen to yield a field of view in the cameras which covers approximately the same field of view as in the surgeon's eyepieces. See the CAD model exploded assembly diagram here [1-page PDF file].



This is a similar assembly to the LCTF attachment above, but uses a Thorlabs FW103S/M motorized filter wheel for filter switching instead of a costly tunable filter. The filter wheel (large black round item) is computer controlled by a stepper motor (left) for rapid switching (55 milliseconds/switch). The front end (right) fits Zeiss OPMI surgical microscopes, including an f=125mm objective lens and Thorlabs CRM1/M cage rotation mount with polarizer element, and the back end (top) provides a diagonal mirror and Apogee camera 2"-24 thread mount. See the CAD model exploded assembly diagram here [1-page PDF file].

Another example of polarization microscopy work is my copying of a rare Leica polarization filter holder [2-page PDF file]. This is a filter slider that slightly tilts the filter elements to avoid surface reflections.



The diagonal adapter can also be fitted to the Haag-Streit BQ900 slit lamp via the standard beamsplitter port. The Haag-Streit coupling is similar to, but incompatible with, the Zeiss type.



This is the diagonal adapter on a Haag-Streit BQ900 slit lamp, shown assembled with a Canon 40D digital SLR.



This longer focal-length version of the adapter for the Haag-Streit BQ900 works with full-frame cameras, shown here with a Sony E-mount bayonet fitting and Sony A7S mirrorless camera. This is readily configured for Canon or Nikon full-frame DSLRs.



This is the diagonal adapter fitted to the Topcon SL-2D slit lamp via the Topcon beamsplitter. This also fits the Topcon SL-2E, SL-5D, SL-6E, and the Topcon OMS-70 operating microscope. Technical details and more photographs are here.



HD Video Camera Adapter for Zeiss OPMI binocular

Instead of using the Zeiss OPMI beamsplitter for camera mounting, it is also possible to adapt cameras directly to the eyetubes of the binocular in place of the eyepieces. Later models of the Zeiss OPMI binocular provide eyetubes with magnetic clutches to hold the eyepieces in place, instead of the older sliding friction fit or screw-on attachment. The adapter shown here couples an HD video camera to this magnetic eyetube mechanism. I produced this adapter to work with small flash-memory HD video cameras such as the Canon HF20, Canon HF200 (shown in the photo), and Canon HF M300. Newer HD video camera models also work well as long as they provide a 37mm filter thread (or other standard size thread) for attachment to the adapter. The single camera shown here records ordinary HD video and high-resolution still photos, as well as providing a live 1080p video feed to an HDTV. See below for a 3D camera-pair version.



This is a close-up of the HD video camera adapter itself. The threaded end fits the filter threads of the video camera; the other end precisely fits the Zeiss magnetic eyetube socket. Optics in the adapter afocalize the Zeiss instrument's image with a field-of-view angle for an appropriate cropping to the HD video frame width. More photos for this project are here.



This slighly different custom adapter fits the Zeiss OPMI Visu 200 binocular (f125) instead of the f170 on the Zeiss Lumera binocular. The receptacle shape of the eyetubes is identical, but the magnetic clutch mechanism differs. On the eyetube you can see the tiny setscrew we have added to lock the camera adapter into the eyetube and to lock the rotation of the camera.



Another project involved generating live 3D video from a Zeiss OPMI Lumera operating microscope from the binocular eyetubes. A pair of HDMI video signals from a pair of low-cost HD video cameras mounted on the two Zeiss OPMI eyetubes feeds into a video processor to produce live 3D HD video on a 3D HDTV. For the 3D application, each of the two cameras must be rotationally aligned to the other, so I replaced the original Zeiss magnetic eyetube with a custom thumbscrew type eyetube to provide a locking rotational adjustment.

Another constraint for the 3D application is that the optical axes of the two Zeiss eyetubes will only separate to about 75mm maximum distance, which puts the two cameras very close together. While the compact HD cameras are small enough to fit inside this constraint, the HDMI output connectors are located on the right side of the cameras, blocking one of the connectors when the cameras are closely mounted side-by-side as shown. The solution is to invert one of the cameras so that the HDMI connector on each camera is located to the outer side. The 3D video processor provides the option to invert the images, so the inverted camera image can me returned to upright like its mate. Inverting one camera also allows both built-in camera displays to fold out like wings as shown. The 3D processor also provides an X and Y frame shift to cover the remaining degrees of freedom required to align the image pair for a properly calibrated 3D effect.



The device at left is my design of a laser collimator used to construct, test, and perfect Zeiss OPMI attachments.

In Zeiss operating microscopes, the two optical paths constituting the left and right pair of stereo views are precisely aligned in parallel. An adapter to attach a single camera to one side or the other does not have to be too precisely centered, so ordinary machining and mechanical assembly will provide sufficient alignment. But in applications where an attachment simultaneously uses both images, such as 3D viewing or photography, the optical axes of the attachment must be more precisely parallel than ordinary machining tolerances will provide. If this precise parallelism is not maintained, the two images of the stereo pair will not be centered with respect to each other. Uncentered images produce a binocular view which the eyes cannot visually converge, or a 3D photograph with displaced centers that cannot be live-viewed.

The principle of the collimator is to produce (1) two laser beams (2) spaced on the OPMI standard spacing of 22mm alongside the central axis, which beams are also (3) precisely parallel to each other, and (4) precisely normal to the mechanical face of the collimator. Each beam thus has four degrees of freedom requiring precise control, consisting of a position and angle each for both left/right and up/down directions. The position is automatically established by the sphere size (conveniently, these are readily available as precision polyacetal bearing balls) and by the precise machining of the clamping mechanism to hold the spheres. The angles are precisely adjusted by manually pivoting the spheres within the clamp. In practice the alignment is done by holding the collimator in a steady fixture, and projecting the laser spots across a room-sized distance to a vertical wall. To locate the projection of the central axis, a precision mirror is attached to the face of the collimator, and a third laser beam is reflected from the wall to the collimator and back to the wall. All these lasers can be inexpensive modules such as are used in laser pointers. Once this projection of the central axis is located and marked, the target projections of the left and right paths are marked on either side at the standard 22mm separation. A one-time calibration is then performed as follows: The spherical clamp is loosened, the spheres holding the lasers are nudged gently by hand until the beam spots fall upon the left and right targets respectively, and the clamp is tightened.

Precise parallelism to 1 minute of arc can be considered a high standard for optical instrumentation. One minute of arc is about the limit of visual acuity of the human eye, making it more than sufficient for direct visual instruments. One minute of arc also exceeds the resolution of 4K high-definition photographs over a wide-angle 45 degree field view. When projected to a target 30 feet away, 1 minute of arc corresponds to about 2 millimeters of separation. Mechanically adjusting to this close degree is just barely feasible with the simple type of spherical mechanism and fixturing shown here. The precision is constrained not only by the fineness and rigidity of the mechanics, but also by the laser optics, which in inexpensive focusable laser modules yields a beam waist of about 1 milliradian = 3.4 minutes of arc, which is a spot size that allows centering on the order of 1 minute of arc.

Much higher alignment precision, to about 1 second of arc, is feasible with the old techniques of optical tooling, using tools like alignment telescopes and jig transits, which were perfected in 1940s to 1960s before lasers, and still used for some work today. Indeed, a laser can be considered to be an alignment telescope in reverse, projecting a laser point source along a line of sight, instead of viewing a line of sight against a reticle target. The optical limitations are the same in either case, and the tiny laser pointer optics cannot perform as well as the much larger optical tooling. In the Zeiss OPMI application, constrained by the parallel optical path spacing of 22mm, the tiny laser modules fit directly within that spacing, which greatly simplifies the collimator mechanism. Alignment telescopes are much larger, which would require a larger and more complex mechanism to precisely move a single telescope from one side or the other of the stereo pair. Coincidentally, alignment telescopes, to achieve 1 second of arc precision across factory-sized distances, are fixtured on the front with a standard larger version of the spherical mount principle (3.5 inch diameter), with a thumbscrew mechanism on the rear providing extremely fine and rigid adjustment, without which the 1-second precision would not be achievable. The laser equivalent would involve something like a 10X beam expander, which turns a narrow laser source into a broad beam with much less divergence than the usual narrow beam.



This photo shows the front view of the Zeiss OPMI laser collimator with the beams energized. The beams emerge from the spherical mounts and pass through the two large holes in the assembly. The smaller holes near the edge accept 6mm cage mount rods for attaching the collimator to the device under test. The laser pointer modules are wired in parallel and powered by a 3 volt battery source. Fixturing may be attached via a 1/4-20 tripod mount on the bottom, which also accepts optical breadboard posts such as is shown here.

This photograph exhibits the dodging technique for photographing laser beams. It is actually two photos of the same scene, combined in Photoshop to create a double-exposure effect. The first photo was with normal studio lighting and the camera tripod mounted. The second photo was of the same scene, but a 30-second time exposure in a darkened room with the lasers energized. During the 30 seconds I swept a handheld white card along the beams. This essentially integrates a spatial map of many point samples. See more about this beam-dodging photography technique on my optical prototyping page.



This adapter fits C-mount cameras to the Zeiss OPMI instruments, shown here with a typical camera, the Panasonic GP-KH232 high-definition module. This camera provides 1080p HD video via a HDMI or RGB connection from a separate controller. The rectangular body shown here is tiny, less than an inch-long cube. The adapter is very compact due to its lack of a mirror diagonal, which mirroring is performed in the camera controller, a rare but valuable feature for instrumentation cameras. Various focal lengths can be fitted into this adapter to provide various crop ratios for different camera sensor sizes. This photo shows the 35mm focal length version. See detailed mechanical diagrams here for an updated design, as well as the installation instructions.



Here is the same adapter, showing its two components separated from the Panasonic GP-KH232 camera. The middle component contains the focal lens cell with C-mount threads. This cell also provides focus calibration and image centering adjustments. The sleeve on the left fits the Zeiss OPMI accessory fitting and also provides rotational alignment of the camera, since C-mount threads stop at a random orientation and do not align rotationally.

The Panasonic GP-KH232 camera (details) is based on the Sony IMX036 HD video chip (details). Other C-mount instrumentation cameras using this chip include the Point Grey Flea 3, a USB 3.0 interfaced camera (details) , and the Leopard Imaging LNC-Q10 H.264 Ethernet/wireless camera (details). The current version of this adapter fits the Panasonic GP-US932A HD Series C-mount cameras.



This shows the adapter and camera mounted on an Zeiss OPMI beamsplitter on a Zeiss 125/16 slit lamp. The same accessory fittings and beamsplitter are used on Zeiss operating microscopes. The adapter shown here (25mm focal length) nests entirely within the OPMI fitting, as does the camera's turret, leaving only about an inch of the tiny camera projecting out from the beamsplitter. The cable runs to a separate controller box which provides HD video signals for live display on a standard HDTV and/or digital recording.

See additional photos on the Zeiss OPMI to C-mount adapters. See also the detailed assembly diagram [PDF file].



Panasonic HD Video Camera Adapter for Zeiss OPMI and Möller instruments

This adapter connects a Panasonic HD video medical camera (Panasonic model AG-MDC10 camera with AG-MDR15 recorder) to Zeiss OPMI instruments. More photos for this Zeiss project are here. This same adapter principle can adapt the Panasonic professional video camera AG-HCK10G (with AG-HMR10 recorder) to various microscopic instruments for non-medical applications.



This is the same type adapter, except fitted for a Möller-Wedel surgical microscope beamsplitter, shown with the medical Panasonic AG-MDC10 HD video camera. More photos for this Möller project are here.



Modifying the Microsoft Lifecam Cinema and Lifecam Studio for Instrumentation Applications

At left is an example of how I modify the the Microsoft Lifecam Cinema (720p HD) and Microsoft Lifecam Studio (1080p HD) cameras for scientific and medical instrumentation. The Lifecams are USB cameras with amazing high-definition video performance, especially considering their street price of about $50 to $100. They also have the rare virtue among webcams of being housed in a cylindrical metal shell, so they can be easily fitted into the cylindrical geometry typical of optical instrumentation, in many cases with no modifications, using a relatively simple mechanical adapter. Compare this to the format of the GoPro HD Hero portable cameras, which are larger and rectangular, and not readily modified, optically or mechanically.

The most valuable potential is that the Lifecam cameras, when disassembled for the "guts", can be placed into custom housings with new lenses or no lenses at all, a technique which I have developed after amateur astronomer Gary Honis. For example, the assembly shown in the photo uses a modified Lifecam with custom lens assembly to turn an ordinary handheld ophthalmoscope into a digital retinal camera.

The original Lifecam lens is of very high quality but nevertheless provides only a very wide-angle field of view not suited to most instrumentation purposes. I remove this original lens and substitute a custom fitting for stock M12 lenses or C-mount lenses. This converts the Lifecam into a configurable fixed-focal-length HD camera for fitting with infinity, macro, or microscopic optics. The entrance pupil collimates to any visual eyepiece, even very short eye-relief eyepieces that would vignette with the usual digital camera lenses.

Removing the lens and substituting an appropriate custom mechanical fitting, such as a C-mount receptacle, yields a camera for direct projection with a format of 1/4" (Lifecam Cinema) or 1/2.7" (Lifecam Studio). The camera then becomes a direct HD replacement for older 1/4" or 1/3" SD (standard-definition NTSC or PAL) video cameras.

The Lifecams are thus seen to be a versatile and cost-effective basis for imaging, but they do have several limitations. While they produce HD format video, they do not produce any standard video output signal such as HDMI. Instead they are USB-only devices which must be tethered to a Windows computer with Microsoft's proprietary driver to view or record the images. The video/still viewing/recording application Microsoft provides is not very sophisticated, but the camera hardware drivers are properly implemented so that they work with standard video and studio applications such as National Instruments Labview, Adobe Premier, and the free and essential gem called virtualdub.

The power consumption of these cameras is such that they must be housed in metal fittings which act as a heat sink. To dissipate heat they also cannot be located completely inside of closed assemblies without a provision for external cooling.

Normally with any CCD camera one must block infrared to avoid unintended lens aberrations and unnatural color in the image. The original lens of the Lifecam contains an integral infrared blocking filter (IR cut filter), so when replacing the lens one must typically provide an IR cut filter for visible light applications; otherwise one has an near-infrared-sensitive camera. Should IR response be desirable, then removing the original lens and filter may be appropriate.



This is again the Microsoft LifeCam Studio 1080p HD camera, which I have modified by removing the stock exterior and replacing it with a custom metal sleeve, and replacing the stock wide-angle lens with a 50mm f/2 telephoto lens adjusted to a close focus, yielding a macro zoom effect. This lens provides a 55mm wide by 31mm high (2.2 by 1.2 inches) field of view at 500mm (20 inches), comparable to a 400mm lens on a 35mm format camera. The assembly is about 30mm (1.2 inches) diameter by 90mm (3.5 inches) long, weighing but a few ounces. The intended application is an eyeglass-mounted HD video recorder for surgical or laboratory procedures. In microscopic terms, the resolution is a remarkable 10 lp/mm at a working distance of 500mm, many times better than unaided visual resolution, making the enlarged HD display of the scene photo-realistic.



Canon Viewfinder Magnifier-Inverter

This viewfinder magnifier (see detailed description page) for Canon digital SLR cameras is a custom telescopic component I make, which provides a 2X magnified and inverted enlargement of the standard viewfinder. This is designed to compensate for the inverted view resulting from adaptation of certain instruments, such as the direct coupling to a Topcon TRC-50VT retinal camera described above.



Topcon TRC-JE and TRC-FE Retinal Cameras

This custom adapter retrofits a Topcon retinal camera to use a Canon or Nikon digital SLR camera instead of the original Topcon 35mm film camera. Pictures and technical details are in the installation instructions for Canon cameras [826 KB PDF file] and installation instructions for Nikon cameras [298 KB PDF file]. You can also order online.

A peculiarity of retinal camera optics is that the image produced by the instrument is upright, while a normal camera lens produces an inverted image. A specially modified SLR film camera back was therefore part of the original retinal camera system This special camera provided a non-inverting, periscopic, mirror-mirror type viewfinder. Ordinary SLR cameras provide a mirror-pentaprism type viewfinder, which inverts the incoming image, the net result then being an upright view when an ordinary camera lens is attached. Putting a digital SLR camera with conventional viewfinder on a retinal camera results in an inverted view in the viewfinder. Some photographers simply accommodate this inversion, or optionally my inverting viewfinder magnifier can be attached to provide an upright view.

Topcon also configured variations of this instrument designated as TRC-FET, TRC-FET3, and TRC-FE3, depending on whether it was equipped to for fluorescein angiography in addition to color photography ("F"), whether the camera mount tilted on a pitch axis ("T"), or whether the instrument had a power supply capable of fast exposure repetition with high flash energy ("3"). All variations are suitable for digital upgrade.



This thin threaded bushing adapts a 2"-40 threaded instrument to a M58x0.75 lens thread. Note the split ring design which prevents seizing of the small pitch inside threads on the large outside diameter instrument. Note also the small dimples (1/16" diameter x 1/16" deep) for a spanner wrench tool to insert and remove the adapter.



This is a custom adapter for a 1.162" outside diameter Bausch & Lomb eyepiece to C-mount (1"-32) lens thread.



This is a custom adapter for a 1.25" outside diameter telescope eyepiece to an M50x0.75 lens thread. Opposing Nylon thumbscrews lock the eyepiece in position, while allowing vertex distance adjustment.



Selecting a Camera for Digital Photomicrography

I've had inquiries about what "consumer" or "prosumer" digital cameras are good for adapting to photomicrography. Some criteria of desirability are:

Accessory threads that permit flush mounting of an adapter: Sadly, current digital cameras such as the compact consumer types have almost all eliminated this feature in recent years. Such threads used to be more commonly provided for the mounting of filters on the front of the camera lens, but this option has apparently become unimportant to casual point-and-shoot photographers. Some cameras with turret type lenses have threads or a bayonet fitting on the camera body which accepts a special adapter tube which surrounds the turret and terminates in standard filter threads; this is an acceptable compromise. This tube is often called a "conversion lens adapter" (CLA) because it it meant to be used to attach a "conversion lens", A "conversion lens" is essentially a short Galilean telescope which you attach in front of the normal camera lens to increase the magnification and thus convert the effective focal length of the built-in lens for a telephoto effect. One can also make this Galilean telescope with less than 1X magnification, and thus decrease the effective focal length and obtain a wide-angle, fisheye effect. Since the manufacturers typically use a standard filter thread size, these tubes are suitable for attaching filters and microscope adapters.

Sadly, current digital cameras such as the compact consumer types have almost all eliminated this feature in recent years. Such threads used to be more commonly provided for the mounting of filters on the front of the camera lens, but this option has apparently become unimportant to casual point-and-shoot photographers. Some cameras with turret type lenses have threads or a bayonet fitting on the camera body which accepts a special adapter tube which surrounds the turret and terminates in standard filter threads; this is an acceptable compromise. Optical dimensions close to the human eye: This permits a direct optical path for through-the-eyepiece afocal coupling, and avoids vignetting. See the section on Understanding and Avoiding Vignetting below. Large lenses, such as are found on better snapshot cameras and SLRs, have a deeply entocentric entrance pupil which introduces unavoidable vignetting in an attempt at afocal photomicrography; such camera lenses can only be adapted with a photo eyepiece, which is a more expensive adapter incorporating optical elements. Inexpensive cameras today tend to have the appropriate lens pupil in a turret form, but lack accessory threads.

This permits a direct optical path for through-the-eyepiece afocal coupling, and avoids vignetting. See the section on below. Large lenses, such as are found on better snapshot cameras and SLRs, have a deeply entocentric entrance pupil which introduces unavoidable vignetting in an attempt at afocal photomicrography; such camera lenses can only be adapted with a photo eyepiece, which is a more expensive adapter incorporating optical elements. Inexpensive cameras today tend to have the appropriate lens pupil in a turret form, but lack accessory threads. Manual modes for aperture, shutter, and focus: Afocal photomicrography typically requires that the aperture be manually fixed, since wider aperture sizes may introduce vignetting. Manual shutter control is not strictly necessary, but it is convenient for adjusting the exposure of difficult microscopic scenes. Focusing is best accomplished by the manual instrument adjustments, not by hunting with the camera's autofocus algorithm. Inexpensive digital cameras today typically provide such a manual mode, although this was not the case during the early years of digital photography.

What cameras sold today are suitable? Cameras at very low cost (less than USD $200) have become available which meet all the above desirability criteria. The Canon A630 is an example of an ideal camera for digital photomicrography. It also provides a live video-out preview, so you can then attach a video monitor to your instrument. Canon changes models very frequently, and in 2013, the point-and-shoot models with suitable features are the following from the A-series, G-series, and S-series models:

Canon Point-and-Shoot Cameras Suitable for Eyepiece Photomicrography

Model list updated as of May, 2013

Most of the models listed are older and not currently sold new by Canon

(But used specimens are widely and cheaply available) Canon Model

[Note 1] Articulated

LCD screen LCD

Size Remote Capture

[Note 2] Live Video

NTSC/PAL Canon

CLA tube Aftermarket

CLA tube(s)

[Note 3] Canon A510 No 1.8" Yes Yes LA-DC52F Bower A52B510C

Sakar JA-A80-52 Canon A520 No 1.8" Yes Yes LA-DC52F Bower A52B510C

Sakar JA-A80-52 Canon A540 No 2.5" No Yes LA-DC52F Bower A52B510C

Sakar JA-A80-52 Canon A570 IS No 2.5" No Yes LA-DC52G Sakar JA-A570-52 Canon A580 No 2.5" No Yes LA-DC52G Sakar JA-A570-52 Canon A590 IS No 2.5" No Yes LA-DC52G Sakar JA-A570-52 Canon A610 Yes 2.0" No Yes LA-DC58F Bower A52B610C

Sakar JA-640-52 Canon A620 Yes 2.0" Yes Yes LA-DC58F Bower A52B610C

Sakar JA-640-52 Canon A630 Yes 2.5" No Yes LA-DC58F Bower A52B610C

Sakar JA-640-52 Canon A640 Yes 2.5" Yes Yes LA-DC58F Bower A52B610C

Sakar JA-640-52 Canon A650 IS Yes 2.5" No Yes LA-DC58J Canon A700 No 2.5" No Yes LA-DC58G Canon A710 IS No 2.5" No Yes LA-DC58G Canon A720 IS No 2.5" No Yes LA-DC58G Canon G3 Yes 1.8" LA-DC58B Canon G5 Yes 1.8" LA-DC58B Canon G6 Yes 2.5" LA-DC58D Canon G7 No 2.5" Yes Yes LA-DC58H Sakar JA-G7-58 Canon G9 No 2.5" Yes Yes LA-DC58H Sakar JA-G7-58 Canon G10 No 3.0" Yes Yes LA-DC58K Sakar LA-G10 Canon G11 Yes 2.8" No [Note 6] Yes LA-DC58K Sakar LA-G10 Canon G12 Yes 2.8" No [Note 6] Yes, also 720p

HDMI playback LA-DC58K Sakar LA-G10 Canon S2 [Note 4] Yes 1.8" Yes Yes LA-DC58E Canon S3 [Note 4] Yes 2.0" Yes Yes LA-DC58E Canon S5 [Note 4] Yes 2.5" Yes Yes LA-DC58E Canon S90 No 3.0" No Yes None Lensmate 37mm adapter Canon S95 No 3.0" No Yes, also 720p HDMI None Lensmate 37mm adapter Canon SX1 [Note 5] Yes 2.8" No No

(records HD) None Lensmate 58mm adapter Canon SX10 [Note 5] Yes 2.5" No No

(records SD) None Lensmate 58mm adapter Canon SX20 [Note 5] Yes 2.5" No No

(records HD) None Lensmate 58mm adapter Canon SX30 [Note 5] Yes 2.7" No No

(records 720p HD) None Lensmate 58mm adapter Canon SX40 [Note 5] Yes 2.7" No SD only

(records 1080p HD) None Lensmate 58mm adapter Canon models A460, A470, A530, A550, and A560 are not suitable (lens-adapter bayonet omitted).

Likewise all SD and most SX models (except as listed above). Sorry!

However, see my custom adaptation of the SD750 and SD790 above.

After 2009, no Canon point-and-shoot camera provided an accessory fitting except the Canon G11/G12! Older Canon models A80 and A95 are suitable via the LA-DC52F CLA tube.

Note 1: Don't be confused by the "IS" designation appended to some Canon model numbers. This is just a redundant emphasis for the image stabilization feature and does not distinguish a model variation. For example, you may see the Canon A650 camera referred to as model A650 IS, A650-IS, A650IS, or just A650; these are all the same camera.

Note 2: Remote capture requires a software application for the PC. Canon includes a basic remote capture application with the camera. Breeze Systems publishes PSRemote for $49 (USD).

Note 3: Every aftermarket CLA tube I've seen is made of sturdy metal, fits well, and costs less than Canon's all-plastic originals. Brands like Bower, Sakar, and Kenko are all well-made, precisely fitted, and generally quite suitable.

Note 4: Canon models S2, S3, and S5 have a deep entrance pupil which will couple only to high-eyepoint eyepieces (eyepieces with eye relief of 18mm or more). Shorter eye relief eyepieces will exhibit vignetting.

Note 5: Canon SX models do not provide filter threads or a CLA bayonet, but they do provide a hood bayonet at the end of the lens which can accept an aftermarket adapter (linked in the table above). Canon does not offer anything but a plastic glare hood for this bayonet fitting.

Note 6: Canon apparently dropped remote-capture support in the G11 and G12 models, after providing it in the G-series up to and including the model G10. See the PSRemote features list.

The articulated LCD screen is a useful feature if the camera must be mounted at an angle that does not permit convenient viewing towards the rear of the camera body. Remote capture which allows you to operate the camera tethered to a PC, which can be an important feature for applications like laboratory data capture. A video-out feature allows you to display the live (although low-resolution) microscopic image on a video monitor or PC, such as for group instruction.

You may also wish to study the eyepiece adapter instruction sheet provided with my eyepiece adapters for the Canon A-series cameras.

For laboratory use, it is often necessary to have direct PC control of the camera, and/or image transfer, via protocols over USB connections like PTP (Picture Transfer Protocol). This allows periodic or time-based taking of photos, or synchronization with other laboratory apparatus or sensors. See Figuiéres excellent page on Digital Camera Support for UNIX, Linux and BSD.

Understanding and Avoiding Vignetting

The "exit pupil" produced by the microscope eyepiece is t