Using the 6 mm Nikon fisheye lens with the Nikon D1 camera

One solution is to optically convert the 6 mm fisheye lens image into a smaller image that correctly fits within the active area of the Nikon D1 image sensor. I built a simple adapter that reduces the focal length by a factor of 1.7 to 3.5 mm efl (a reduction factor of 1.5 would be preferred but was not as convenient to implement). The optical adapter consists of a 50 mm f1.4 Nikon AFD lens attached to the D1. This is attached directly to a reversed 85 mm f2 Nikkor lens by a dual 52 mm macro ring coupler. These two lenses form a high quality relay lens with a magnification of 0.588 (reciprocal of 1.7). A lens coupling tube is needed to position the 6 mm fisheye lens at the correct point relative to the 85 mm lens. This tube has two female (camera body) flanges and should have a flange to flange distance of 93 mm or slightly less. To prove out the concept I assembled the special lens coupler out of miscellaneous Nikon extention tube parts. The lens coupler used the following sequence of Nikon extension tube parts: (1) K3 ring, (3) K4 rings, (2) K5 rings, (1) BR3 ring. Vignetting is possible if either the 50 or 85 mm lenses are stopped down so set both wide open. Use manual or aperture priority exposure mode only. Use the iris on the front fisheye lens only. The focus sensor is operational, but the weight of the auxiliary optics can keep the autofocus from operating correctly. Manual focusing is recommended. The weight of the additional optics onto the filter thread of the 50 mm lens is significant, so some care is needed to not overload this lens. One side effect is that the relay lens system inverts the image so it is seen upside down in the camera viewfinder. This relay lens works with other Nikkor lenses with similar exit pupil locations but is not a general solution for most Nikkor lenses.

The above fisheye image was produced by a Nikon 6 mm f5.6 fisheye lens coupled to a Nikon D1 digital camera via an optical relay. This image has a diagonal field of view of 220 degrees including everything from straight up to 20 degrees below the horizon. (Raw jpeg fine image -- 1.0 mbyte)

One reason that I particularily like the 6 mm f5.6 fisheye Nikkor is that it provides a fast means to produce 360 degree panoramic images. The above image covers 360 degrees in azimuth and 110 degrees in elevation (from the zenith to 20 degrees below the horizon). This image was created digitally converting the polar format image at the top of this page into a rectangular format using Photoshop and Panorama Tools. For more examples and theory, see my Spherecam page.

Use the mouse to navigate in the image.

Use the control and shift keys to zoom.

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Copyright 2000 by Dan Slater, All rights reserved.

