Aquacolor® Underwater Cinematography: Breaking the Available Light and Color Barriers Underwater

By W. Tuckerman Biays

(Presented at the Society’s 125th Technical conference in Los Angeles (paper No. 125-43) on November 2, 1983 by W. Tuckerman Biays, Aquacolor® Pictures, Key Largo. Fla. This article was received June 26, 1984. A similar version of this article appeared in American Cinematographer, August/September 1984. copyright © 1985 by the Society of Motion Picture and Television Engineers, Inc.

Photographs by Alice de P. T. Biays)

This article describes a new system for filming underwater. The Aquacolor® system consists of underwater cameras with patented, state-of-the-art automatic exposure controls, unique metering, and new multiple filter systems that enable underwater cinematographers to capture, as never before, the rich and beautiful colors beneath the sea. Color charts, gray scales, and skin tones are reproduced without artificial lights through at least 40 ft of sea water almost as naturally as through air.

Figure 1. “Nowhere else in the living world does color reach

the variety and dominance that is shown in the coral reef.” Twenty-.four years ago Dr. Marston Bates wrote, “Nowhere else in the Living world does color reach the vari­ety and dominance that it shows in the coral reef. The overwhelming impres­sion, whether of fish or of background, is color; exuberant, varied, striking color”’ (Fig. 1). Unfortunately, mo­tion-picture audiences have rarely seen these vivid colors on the screen. Colors as seen and photographed underwater are severely affected by the massive blue/green filter factor of ocean water (Fig. 2). The red end of the color spectrum attenuates drasti­cally when passing through water. As the depth increases, the light becomes predominantly bluer, causing spectral imbalance. Divers must view every­thing through this heavy cyan water filter, which masks the true colors that are present in the sea. Swimmers’ gog­gles and masks only enable divers to see clearly. They have not yet been designed to rebalance light to enable divers to see clearly in full color. Since most people are not aware of the colors they are missing, there has been no real demand to find practical methods to enable divers to see the full spectrum and brilliance of colors underwater, let alone for recording them on motion-­picture film with consistent reliability. Human vision does make an ad­justment, psychological in part, which allows divers to perceive some of the warm colors of the coral reef world. But film by itself has no ability to compensate for the blue/green filter factor of sea water. This is why skin tones on sun-bronzed divers usually appear cold and lifeless when photo­graphed underwater.

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Figure 2. Colors as seen and photographed underwater are severely affected by the massive blue/green filter factor of ocean water. Unless filmmakers correct for the cyan light, beauty and color remain disguised, and suntanned skin appears cold and lifeless. (Water path =25 ft.) Film directors and producers rec­ognize the severe cyan cast the sea gives their films. Yet, at a time when marvelous technological achievements are being made in every aspect of film and video work, few attempts have been made to establish and pursue scientific norms of color fidelity in underwater cinematography. Today’s film emulsions are capable of recording the full range of colors underwater. Kodak color control patches can be reproduced as faithfully through 40 ft or more of sea water as anywhere else (Fig. 3). Real colors aren’t being recorded because existing exposure controls, light-sensing de­vices, and published in-water color correction data contain inaccuracies which do not cope with the spectral imbalances and light fluctuations en­countered in the sea. Underwater camera equipment has not been pro­vided with precision devices designed specifically to deal with the dynamic exposure and color balance problems that exist in underwater filmmaking. Figure 3. Aquacolor® reveals the complete visible spectrum of colors in the sea. Here color charts, gray scales, and skin tones are reproduced through 35 ft of sea water without the use of artificial lights.

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Figure 4. Aquacolor 16-mm 400-ft movie camera includes multiple composite optical filters with selection devices, and a patented automatic aperture control with a specialized metering system so maintain precise exposure through filters in water.The system automatically compensates for continuously changing effects of reflection, scattering, absorption, and refraction of underwater light and rebalances the color of the light entering the lens, The Aquacolor® System

The components of the Aquacolor® camera system, developed by Larry Westhaver and the author, are multi­ple composite optical filters with se­lection devices, and a patented auto­matic aperture control with a special­ized metering system to maintain precise exposure through filters in water (Fig. 4). Aquacolor® reveals the complete visible spectrum of colors in the sea while filming with ambient daylight. It records the true rich colors and lovely pastels that dominate a healthy tropical coral reef. Films shot in Aquacolor® show appealing suntanned divers instead of green-skinned hu­manoids (Figs. 5 and 6). At the 125th SMPTE Technical Conference in November 1983, a 20-min presentation reel from Aqua­color® Pictures revealed three signifi­cant advances for underwater color filmmaking:

1. Incomparable color saturation, with color charts, gray scales, and skin tones reproduced through at least 40 ft of sea water almost as naturally and vividly as if they were filmed through air.

2. New dimensions in precise ex­posure, automatically.

3. Optimum detail and color in turbid water.

Figure 5. Monochromatic pictures do not offer much contrast or detail for television. (Water path = 25 ft.) Figure 6. Color provides definition. With Aquacolor®, television viewing takes off in a new dimension. (Water path = 30 ft.)

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Problems Encountered

Exposure and Color Balance Perspectives The techniques of above-water photography are not adequate to the task of recording the underwater scene within the tolerances adhered to in cinematography through air. Analyz­ing intensity and color content of light through air is simple. Above water, light is relatively stable and somewhat controllable. Beneath the surface of the sea, however, the intensity and color balance of light can fluctuate frequently and uncontrollably in the time it takes to film even a five-second episode.

Figure 7. A plot of percent of light reflected from a sea surface with varying angles of the sun. The dotted horizontal line shows the constant percent reflected light when the sky is completely overcast (perfectly diffuse light). (Illustration reprinted from Underwater Photography, by permission of the publisher.2)

Maintaining precise exposure in the ocean depends on numerous factors which change continuously. Varying quantities of daylight actually pene­trate the water’s surface, depending on atmospheric conditions, the angle of the sun, and the wave action. Maximum sunlight penetration occurs at rare times on clear days when the water is smooth and the sun is directly over­head. The critical angle of reflection is 48.6º. When the sun is not within 48.6º of being directly overhead, the penetration of direct rays diminishes increasingly due to surface reflection (Fig. 7). On the other hand, surface reflection of diffuse light is relatively constant.

Light that penetrates the surface travels more slowly through water than through air. This results in refraction. The light rays are bent not only at a refractive index of 4/3, but also by the angle of the sun as it passes overhead. The bending increases as the sun moves towards the horizon - thus causing the refracted rays to pass through more and more water before achieving specified depths. Longer water paths result in diminished light intensity because of absorption and scattering.

Dark particles in water cause the light photons to be converted to heat energy, resulting in absorption. In absorption, the light photon is lost as a source of light. Absorption becomes more pronounced with increases in turbidity.

Bright particles in water reflect and scatter light. The concentrated beams of light are broken down into numer­ous weaker beams by particles in the transmission medium. Those photons are lost as directional but not as inci­dent light. There are always varying amounts of algae and other matter in suspension in the sea to scatter light. Since sea water is never totally mo­tionless, quantities and qualities of scatter-producing particles vary con­tinuously between underwater cameras and subjects. Scattering caused both by suspended matter and by micro­scopic vibrations of water molecules results in diffusion. In water, as on land, diffuse light greatly reduces contrast.

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Figure 8. In this photo, made with a 35mm Aquacolor® camera with a 24mm lens, 24 ft deep and 15 ft from the diver, the red “V” inset on the front of the wetsuit is red, even though it is in shadow.



Figure 9. In this photo, made with a conventional 35mm camera with 15mm lens and corrective port, approximately 8 ft deep and 5 ft from the divers, both wetsuits are black in the shadow areas, even though the short suit on the right is red all over. (Photo courtesy Jim Payette.) Other Effects The quality of light and color balance are not the only photographic essentials affected by the sea. The quality of the underwater cinemato­grapher’s thinking is affected also. Water pressure and steady loss of body heat combine to dull the diver’s mental faculties. Calculations and operations that are simple at the surface become progressively more difficult with depth and exposure. Keeping it simple is a top priority for all successful work in the sea. Clearly, a method for continuous aperture control is the most practical way to maintain proper exposure set­tings throughout the changing light levels that are unavoidable in most underwater shots. Unfortunately, the automatic aperture controls currently available are not sufficiently fast and accurate. Also, many current light-sensing techniques become unreliable underwater. Spectral Imbalance in Water Selective absorption of the compo­nent colors in light which passes through water is a more pronounced and complex problem than the changing light levels. For conventional photographic purposes, we learned that in the subtropical water of the Florida Keys and the Bahamas, red is absorbed after passing through about 20 ft of water. Orange disappears after 35 ft. Yellow and violet are absorbed by 65 ft, green by about 75 ft. and blue by approximately 90 ft. Over 100 ft, everything appears gray.

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Customary Attempts to Obtain Warm Colors

Many underwater cameramen and documentary filmmakers shoot with daylight-balanced film and tungsten lights, thinking that the excessive red of the lights will be absorbed by the water. In theory a 16-ft water path will convert 3200K to 5500K. In practice, at a camera/light-to-subject distance of 8 ft, even several 1,000-W lights have insufficient power to illuminate most scenes uniformly.

Philosophy

Evaluating Test Films

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Figure 10. Test films begin with a suntanned diver holding color patches with gray scales in open sunlight just prior to each dive.



Figure 11. At working depths of 20 ft. or more, a diver and color patches are filmed again. The Experimental Aquacolor® Camera In building the Aquacolor® experi­mental camera system, port and lens configurations had to be analyzed and selected for spectral transmission properties and design suitability. Plexiglas ports are less prone to con­densation than are glass ports, and normally, dome ports are preferable. Dome ports shorten the water distances necessary to shoot through, improving image quality. However, close-up shots using wide-angle lenses and dome ports produce pictures with undesirable degrees of forced per­spective, and many close shots would be required. Flat ports also have their special problems. They require longer water paths and create longitudinal chromatic aberrations, which slightly reduce resolution and color saturation.



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In water, a light-sensing system is required which, even through drastic color temperature conversions, main­tains the light intensity (exposure value) specified for various film emulsions. To accomplish this, Westhaver devised a specialized metering system. This metering system is essential for maintaining proper exposure while working through multiple filter variations in ocean water. The sensor must be made to have a specific spectral response, one that covers the entire range of visible light. For the Aquacolor system, the sensor must also have exceptional speed. A type-5 CdS photoconductive cell exhibits a response of the type required. A draw­back of CdS cells, however, is their slow response time at low light levels. For our work, optimum results have been achieved with a unique photo­sensitive field-effect transistor.

An exact, critically-damped, automatic exposure control (AEC) was required. In the dynamic sun-and-shadow underwater environment, panning without precision aperture control is almost certain to produce exposure errors with color shifts within scenes, which lab timers cannot correct. So Westhaver invented a state-of-the-art electro-mechanical device for precision aperture control (Fig. 13). The patented AEC is as indispensable to Aquacolor cinematography as fins are to fish.

In the experimental 16mm Aquacolor movie camera, a Bolex reflex camera was used because uninter­rupted light sensing could be accomplished easily via the beam splitter in the Bolex viewfinder system (Fig. 14). This placed the sensor behind the filter/lens/aperture combination and before the shutter. Therefore, the light sensor reacts to a portion of the same light admitted by the lens. A high degree of accuracy is maintained because the light sensor can activate the correction circuitry to compensate for mechanical errors in aperture ring and gearing. Correct exposure is maintained by sensing light deviation and correcting for it by opening or closing the aperture to the desired degree by means of a servo mechanism. Proper lens aperture setting is maintained constantly, whether the shutter is opened or closed. The aperture control’s precision is not limited by mechanical friction. Accuracy is adjust­able. A threshold circuit is provided to interrupt the power to the dc servo­motor whenever the exposure error is so small that the power supplied either could not cause correction or is photographically negligible. This prevents unnecessary power drain, important in portable, battery-operated equipment.

Figure 13. Some components of the Westhaver critically-damped AEC on a 12-120 lens used for action scenes above water.

Figure 14. Part of the light sensor circuit on the underwater camera.

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The automatic aperture system assures the best possible exposure on every frame of film run through the camera. The aperture control responds to exposure variations as small as 1/32 of an f-stop. The critically-damped system senses light changes and cor­rects for them faster than the eye can detect. Above all, the aperture control system makes it possible to color-correct through filters in water. In practical applications, man simply cannot perform as well in the sea as does the Westhaver automatic aperture control, invented specifically for in-water cinematography.

To hold experimental color-correcting filters, we constructed circular disks with filter ports that could be rotated in front of the camera lens (Fig. 15). Since the filters were inside the hermetically-sealed underwater housing, we used Kodak Wratten CC gelatin filters. They were easy to work with, enabled us to make any combination we needed, and do not bend light passing through them. Figure 15. An old filter wheel set up for selective color absorption tests.

Color Attenuation in the Ocean



Aquacolor uses a system of subtractive filters. Our objective has been to find the workable complements, as recorded by film, to the absorption characteristics of ocean water. To do this, we selectively reduced the component colors of visible light to the level of the weakest component. Ideally, the scene records as if filmed through air. Spectral imbalances are corrected by a series of filters created to comple­ment the water absorption curves for various light transmission distances. The densities of filters used are pro­portional to the light-transmission distances.

First, it was necessary to identify the water path attenuating the various components of the color spectrum as the sum of the distances from surface-to-subject-to-lens, and always in that order. For example, if the diving model is 30 ft below the surface, and the camera is 10 ft below the surface and directly over the model, the water path affecting the color balance is 50 ft long. If model and camera change places, the water path becomes 30 ft. If both are 45 ft deep and 5 ft apart, the water path for color correction is 50 ft. Recognizing how this water path is determined is essential to successful color correction.

The refractive index of light in water causes objects to appear 25% closer than they actually are. Conventional diving masks do not correct for this. Film subjects appearing to be 3 ft away will in fact be 4 ft away. So all lens-to-subject distances as perceived by the underwater cameraman must be multiplied by a factor of 1.33. (This calculated lens-to-subject distance must not be confused with focus settings required for lenses set behind flat ports, which require apparent distance lens settings.) Depth readings are never a problem, as precision ex­panded-scale depth gauges accurately provide the depths of camera and subjects in ft/in.

The attenuation of each of the component colors in the visible spectrum is not uniform and varies with the length of the water paths. It is necessary to balance underwater light for all colors, like green, as well as attenuated reds, oranges, and yellows. If one corrects only for the loss of red, the intermediate colors are left unbalanced. Subtle shades of green, for example, can be distorted to record as inaccurate shades of brown. Each filter has to be a composite of several Kodak Wratten CC gelatin filters. After determining the correct color attenuation values across the visible spectrum, it becomes possible to create a system of selective, computer-generated subtractive filters for every water path through which the camera must color correct. Aquacolor filter calculations produced significant changes from the existing published tables that provide color correcting guidelines for use in water.



To reproduce the real colors without going into over and under color cor­rection, it was necessary to change filters for every 5 ft of water path. Essentially, accurate color correction is achievable at the plane of focus. Beyond that, warm colors fall off.

Different locations and conditions within a given region can produce variant color casts. Florida’s sub­tropical coastal waters inside the coral reefs normally produce a green filter effect. Light passing through pure ocean water has a bluer filter effect and does not attenuate the blue end of the color spectrum as much as coastal water. Water close to shore tends to produce a yellow cast, as does turbid water. In fact, as turbidity increases, selective absorption becomes more significant than selective scattering. With sufficient turbidity, the attenuation of the violet end of the color spectrum becomes greater than that of the red end. The attenuation of the red end of the color spectrum, however, is not caused by particulate matter in the water. It is caused by the molecular Structure of water itself, even of dis­tilled water. For ideal color correction, each condition requires different filter combinations compensating for every length of water path (Fig. 16).

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Whether lighting is directional or diffuse also affects color saturation. When white light falls upon a colored subject, the component parts of the light source that do not match the pigment or dyes of the subject’s surface colors are absorbed. The components of the visible spectrum that are not absorbed are reflected and are per­ceived as the visual sensation we call color. Frequently, however, total ab­sorption of the wavelengths does not occur. That unabsorbed light is re­flected as white light, and is called specular reflection. Specular reflec­tions mix with the colors being re­flected from the subject, and have a canceling, or graying, effect on those colors. Because of specular reflections, bright colors lack saturation on over­cast days, and pastel colors can be difficult to record at all, unless shot close up. When light falling on the subject is highly directional, the cam­era can be positioned in such a way that specular reflections entering the camera lens are minimal. In the rela­tively diffuse light in water, specular reflections are an ever-present prop­erty of light that must be understood if color saturation is to be achieved with any degree of certainty. An un­derstanding of the effects of specular reflections is essential also for realistic analysis of color film tests made in Water. Additional Camera Developments Throughout the developmental years, while performing in situ tests with experimental movie and still cameras, further revisions were created, built, and refined, to improve the total Aquacolor® capability. Figure 16. A plot of percent transmitted light versus wavelength for a water path of loft. From top to bottom, the types of water are: pure, average ocean, maximum coastal, average coastal, and turbid. Notice that the light coming from the pure and ocean waters will appear bluish, from the coastal waters will appear greenish, and from the turbid water will appear yellowish. (Reprinted from Underwater Photography, by permission of the publisher.3)

Figure 17 Control knobs for filters and focus.

Optimum underwater housing weight, balance, and controls are all-important. In air, the present experi­mental 16mm movie camera weighs 42½lb with 100-ft film load, and 561/2 lb with 400-ft film load. In the water, both versions weigh 2 oz. The camera balances well in any attitude for ef­fortless one-handed aim-and-shoot operation. This is a very important design criterion as it leaves one hand free so the underwater cameraman can maintain stability and/or operate the focus, action viewfinder parallax, or CC control knobs during the filming of moving subjects.

Much time and effort went into the creation of multiple filter-wheel de­vices. Equally significant was the de­sign and location of the CC filter and focus control knobs on either side of the viewfinder housing through the top of the housing just over the lens (Fig. `17). There the controls may be oper­ated without interrupting the opera­tor’s view of the subject, either through the viewfinders, or over the top of the camera housing.



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Precise framing throughout tight, fast-moving action scenes is exceedingly difficult to achieve in water. We designed and tested several systems before we devised an effective one for maintaining accurate parallax control of the external action viewfinder even as the camera-to-subject distance changes (Fig. 18). For stationary shots and precision framing, a double lens reflex system was created with parallax adjustments. It is designed to pro­vide an optimum view through the reflex optical system while the operator’s eye remains as much as 9 in. behind the viewfinder port. This provides the operator simultaneously with through-the-lens perspective and an overview of the panorama in front of the camera. This is an important ca­pability for use with a fast-moving subject being filmed close up.

Important readouts are located within the double lens reflex view­finder housing (Fig. 19). One is the brightly lighted electronic exposure readout for verifying depth-of-field. Another is a bright red light that op­erates in combination with a sonic signal, indicating when light levels are too high or too low for the exposure index of the film in use. Warning lights indicate potential filter selection problems also.

There is a flooding alarm so sensi­tive that merely breathing moist air on any of the moisture detection sensors activates both a loud buzzer and a re­peating strobe located outside the housing (Fig. 20). The device has a test circuit, and has never produced a false alarm. Another effective safety feature is the portable vacuum test system. It was devised to enable 90-sec, foolproof leak-detection checks before each dive.

Special runners on the base of the camera housing provide exceptional stability and non-skid features. On unstable boat decks this feature pro­vides protection for both camera and crew.

Exterior lights tell diving models and crew members when the camera is running. A built-in compass and film counter light up for night work (Fig. 21). There is a battery voltage tester for in-use checks. An expanded-scale, precision depth gauge on the camera housing is used in specifying filter se­lections. In short, there are all manner of things to delight the cinematogra­pher with a passion for precision. Figure 18. Depth gauge. Action viewfinder with precision parallax control, adjustable while shooting. Double-lens reflex viewfinder with close-up parallax offsets. Figure 19. Double-lens reflex viewfinder readouts Figure 20. The transparent housings with selector switches contain buzzers, strobe, indicator lights,and night lights which interconnect with circuits within the camera housing and on the camera itself.

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State of the Art Ni-Cad Reliability Like most modern movie cameras, Aquacolor cameras are powered by nickel-cadmium (ni-cad) cells. Un­fortunately, such power supplies re­main the least certain components in today’s electro-mechanical cameras because commonly used ni-cad bat­teries are very desirable in most ways, except one: state-of-charge measuring equipment has not existed to provide the user with the precise ampere-hours (Ah) of capacity available to operate the cameras. The only way a camera­man can be certain his ni-cad batteries are fully charged is to give them a full charge - regardless of the cells’ in­determinate existing state of charge. Thus the cells get gassed, lose their charge balance, and their life is shortened abruptly, along with that of the entire battery pack. To overcome these limitations, Westhaver Associates invented a unique ni-cad charger/evaluator (Fig. 22) which eliminates overcharging, maintains balance charge, pinpoints defective cells, and removes the ni-cad limitation “memory-type” phenomenon. It tells precisely what number of Ah have been accepted during charg­ing and are available to operate equipment. The charger/evaluators extend the operating time and life ex­pectancy of the costly batteries. Most important, they increase the reliability of the battery systems at least by an order of magnitude, i.e., tenfold. Figure 21. Transparent starboard instrument pod with "camera running” lights and compass.

Figure 22. Ni-cad charger/evaluator (Illustration by JoAnn Turner Westhaver)

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Underwater Communications One of the underwater filmmaker’s most significant handicaps has been inability to talk to his diving actors and support divers on the “set.” In an age of advanced science, it is difficult to believe that communications beneath the surface of the sea are not good; in fact, there are hardly any at all. Most manufactured wireless underwater systems for verbal communication between film directors, cameramen, crew members, actors, and support vessels are so unworkable that hand signals and slates remain the standby. Figure 23. Underwater full-face mask containing microphone developed by W. T. Biays for distor­tion-free, wireless underwater communications. Listening divers need no equipment to hear.

What was needed was a microphone which would remain waterproof at any depth of pressure, yet would retain the sensitivity to transmit clear voice-sig­nals without the usual distortions that are normally generated within full face masks with demand regulators. After a year of R&D, we accomplished this (Fig. 23). Then it was a simple matter to modify conventional, powerful acoustic energy underwater commu­nications units to provide direct, relatively normal, undistorted conversation between divers and/or their support vessel. The powerful acoustical trans­ducers (underwater loudspeakers) generate waves through water that move divers’ eardrums just as sound waves do in air. This means that listening divers do not have to be equipped with special underwater receiving equipment to hear, and the cameraman/director can talk to his assistants and diving models or actors without taking time to go to the surface to issue instructions. The cam­eraman also can direct people while he is filming them. This saves many scenes that otherwise would have to be interrupted and begun again.

Automated Aquacolor camera systems operate almost with point-and-shoot simplicity and speed. Because of hyperfocal settings, it is usually only necessary to frame and shoot. The cameras really do keep frustration levels low and productivity high. The automatic exposure control frees the cameraman from purely mechanical functions, enabling him to concentrate more fully on the purpose of his craft: to capture the action and create suc­cessful compositions. The Aquacolor camera systems have lowered our clients’ and our own production costs significantly. The 4:1 shooting ratio of the 22-mm underwater film that demonstrates this paper is one example.

Problems of exposure and color balance are minimized for the film labs. To match skin and hair tones recorded 30 ft underwater by Aquacolor cameras with those recorded in scenes shot above water, requires no more than the moderate amount of lab timing normally used for films shot en­tirely out of water. Bracketing and/or re-shooting for exposure and/or color balance is never necessary. The amount of usable footage produced by the experimental Aquacolor camera is exceptional.

Aquacolor cameras make it possible to record natural, rich colors through more water than is possible with con­ventional lighting systems without the considerable expense, confusion, turbidity, and danger of lighting equip­ment, crews, and vessels with huge, noisy generators. Since these cameras continue to produce outstanding foot­age where poor visibility would delay or spoil conventional film operations, underwater film productions are less likely to be put off by fickle conditions of sea, visibility, and turbidity.

Despite the variety of composite filters, optics, electronics, and ni-cad batteries compacted within the Aquacolor camera housings, the units are reliable, manageable, and simple to operate. The aperture controls are made with no inherently fragile components. Through many years of de­veloping, testing, modifying, and making film, we never experienced a breakdown with any Aquacolor sys­tem. The cameras are so simple to operate they can be handed over to non-photographer divers with only one or two minutes of instruction.

For many years Aquacolor cameras have awaited a sufficiently high-speed, “warm” film, because Aquacolor filter combinations cost f-stops. When Eastman color high-speed negative film 7293 became available, that problem was solved. With help from Clay Kelty, president of Continental Film Lab in Miami, we quickly learned to optimize the best qualities of the new film while minimizing any disadvantages. We used E.I. 400, the prescribed Kodak Wratten 85 daylight conversion filter, and normal processing. Since ocean water contains particulate matter, grain is no more apparent than in films shot with the 7247 finer-grain color negative film.

When filming in the sea with ambient light, an important consideration is the scene’s lighting contrast. A typical scene might contain a swimmer with his back in direct sunlight, but his face and chest in complete shadow. The Eastman color negative film has a 4:1 luminance ratio that not only reproduces the portions of the scene in direct sunlight as desired, but additionally records the shadow details and colors. Normally, such shadow details and colors can be recorded only with the use of traditional fill lighting either from artificial lights, or from working over a highly reflective sand bottom in shallow, clear water.

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In underwater work where sun and shadow are relatively uncontrollable, an unusual characteristic discovered was the high-speed film’s ability, through Aquacolor filters, to record colors in shadow areas with no signif­icant color shift from what is recorded in direct sunlight. We also learned that in the diffuse light and specular re­flections in the sea, with the Aquacolor filters, outstanding Eastman film records the intermediate pastel colors almost as well as through air. We learned in our work that with the new film we can rely on a camera exposure latitude that spans seven f­stops when counting the shoulder and toe densities. This is essential to Aquacolor, because working through the dense Aquacolor multiple-filter combinations, the underwater cinem­atographer requires every bit of the exposure latitude provided by the new Eastman negative film. With Eastman 7294, it was even possible to film an air lift salvage op­eration with available ambient light through 40 ft of dirty water between 5 and 6 p.m. Despite the turbidity and flat light, the details and colors turned out so well that the scenes were in­cluded in a high-budget commercial.

Aquacolor pictures create optimum detail in turbid water.’ Long shots of scenes made on squally days, 22 ft underwater with visibility limited to 25 ft, aren’t very usable to filmmakers as a rule. But with Aquacolor, the results can be very usable. On 16mm film strips, color provides definition. For this reason, Aquacolor cameras “see” better than the divers who operate them. But this is only because we haven’t applied Aquacolor technology to diver’s masks yet. The low-contrast problems inherent in underwater films are overcome by the unique color contrast in Aquacolor pictures. With the brilliant color satu­ration of the Eastman color high-speed negative film, the color-corrected subjects contrast dramatically with distant, relatively cyan backgrounds in many scenes. By analyzing foreground and background objects, the Aquaco­lor cameraman/director can make the contrasts work to advantage to create striking, 3-D-like effects. The Eastman color high-speed negative film’s brilliant color satura­tion produces a quantum leap forward for Aquacolor. Most important, 7294/5294 film provides the speed required for Aquacolor systems to operate successfully through most of the same water paths that non-Aqua-color cameras worked through previously.

Finally, Aquacolor techniques are completely practical to use in all sorts of commercial applications through 40 ft and more of water. Together with the Aquacolor technology, the East­man color high-speed negative film creates an exciting and colorful new era for underwater cinematography.



Aquacolor Supplemental Lighting

Figure 24. 650-W lamps, shown without beam diffusers or compensating filters, were developed to operate from a generator set at 1361/4 V. The lights weigh 2 oz in sea water, and are designed to augment, not replace, ambient light

Provision has been made for additional light sources when ambient light is insufficient, such as for night filming or for fill lighting in dark shadow areas. Each camera grip has special attachments for quick-connecting spring-latched light arms in water. Lights on each side of the camera are provided with expandable, jointed arms that allow the lights to be aimed at subjects at 45 degree angles. This minimizes backscatter and flat lighting.

Since existing lighting for under­water applications produced incorrect color balance and/or hot spots, ex­perimental daylight color temperature lighting systems were developed to complement the Aquacolor camera systems. Self-contained 12-V battery-operated lights serve close-up applica­tions such as under ledges, in acute turbidity, etc. We are experimenting with battery-operated xenon arc lights to replace tungsten-halogen ones.

For more far-reaching applications, a set of six 650-W lamps were devel­oped and built (Fig. 24) to operate from a 136-V generator via a ground fault circuit interrupter (Fig. 25) and then through 220 ft of cable by way of an electric-drive cable reel with col­lector rings (Fig. 26). Floats are at­tached to the cable to keep it from hanging up in the reefs, and to eliminate the need for diving and surface cable tenders. Each set of lights weighs 2 oz in sea water. All lights are designed to augment, not replace, ambient light -- except, of course, at night. The 120-V lights do this so well with Aquacolor daylight conversion filters that often it is necessary to consult records to tell if pictures were shot with or without the help of the supplemental lighting. There is no hint of hot spots with these lights. Everything within the plane of focus is lighted uniformly.

One pays an illuminance penalty when daylight filters are used over tungsten lights. We performed calcu­lations and made up experimental Aquacolor filters to use in front of the camera lens in conjunction with 3200K lights, in an attempt to extend the “reach” of the lights. The results of the tests in daylight were disappointing. Trying to color-correct in daylight with tungsten lights produced unreliable results. The attenuation of the red color from the lights was too abrupt and critical to maintain the precise water path to match the attenuated red of the light with the required filters. The inescap­able fact is that where serious scene-to-scene color-correct pictures are required, mixing light sources with sig­nificantly different color temperatures essentially is unworkable - especially underwater.

At night tungsten lights work well. Then they become the only light source, and are not being used in an impractical attempt to replace ambient daylight. With the battery-operated Aquacolor lights, Aquacolor cameras continue to produce optimum results even when visibility is 2 ft or less due to extreme turbidity. Test results have been remarkable. With the experimental lights, backscatter is minimal - almost nonexistent to all practical intents. This is made possible by the use of two low-power lights on special arms that locate and aim the lights where they do not light the water between the lens and subject. The detail and color thus recorded on film are almost equal to that of film made in clear water - even though the cameraman who views the subject from behind the camera, which is a greater distance than lens-to-subject, may see relatively indistinct subjects as he films. Obtaining color-correct pictures at night with portable 120-V lights is fairly simple. ("Portable" lights are anything divers can swim around with, usually 1000 W or less per element.) We eliminate the Wratten 85 filters, and use 3200K lights with diffusers which eliminate hot spots and spread the light uni­formly over an angle of 70 degrees.

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Figure 25. Self-tending vessel includes ground fault circuit interrupter for safety in using generator-operated 120-V lights underwater, and remote control and meters for maintaining precise voltage and color temperature at the lights.

Maintaining correct voltage at the lights is important. With generator-powered 120-V lights, voltage drop is appreciable in cables light enough to be manageable in underwater work. For example, calculations show that six 650-W, 3200K lamps rated at 120 V and powered through 220 ft of No. 12 AWG cable produce a voltage drop of 16-1/4 V through the cable. Theoret­ically, each volt of change causes a 10K shift. Without compensation, this would lower the Kelvin temperature of the lights to 3037-1/2K. In this instance, setting the generator governor to boost the voltage to 136-1/4 V will provide 120 V and 3200K at the lights. (Generators are notoriously overrated. So the gen­erator(s) must be more than adequate. Also, never rely on a vessel’s generators already set up as part of the ship’s service.)

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As we know from conventional film work, to maintain a constant exposure setting, the power (wattage) must be doubled every time the light distance is increased by a factor of 1.414 (the square root of 2). Thus if we assume clear water with negligible loss, it is necessary to quadruple the watts every time we double the water path (lights-to-subject-to-camera lens). Conversely, the intensity falls off as the square of the distance (water path). So every time we double our water path, theoretically it costs us at least two f-stops. Consider a hypothetical case (Table 1). Given: the camera-to-subject dis­tance is 1 ft and the light-to-subject is 1 ft; the water path is 2 ft. Assume two pairs of 650-W lights with diffusers produce a T-stop of T/22 at this 1-ft camera/light-to-subject distance. If we move the camera and lights back to positions 2 ft from the subject, the re­quired aperture setting for the 4-ft water path would become T/ 11. At 3 ft each, the aperture would have to be opened to T/7. At 4 ft, the aperture required would be T/5.6. At 8 ft, T/2.8 would be required. Of course these hypothetical settings do not take into account scattering, absorption, and corrective filtration. In practice, portable lights cannot adequately il­luminate entire scenes 8 ft away. * Figure 26. 220 ft of cable supply voltage to the 120-V ac movie lamps through a motor-driven monel cable reel with collector rings. Floats clip onto the cable to provide neutral buoyancy, both so that it does not snag on coral and to eliminate the need for extra support divers to tend the cable.

It is evident that for close-up filming with artificial lights, detrimental ex­posure changes result when camera/ light-to-subject distances are not maintained within 6-in, tolerances. The dynamics that exist while working in the sea with hand-held, portable cameras and lights are such that it is only with the Westhaver aperture control that we can be assured of ob­taining correct exposure throughout every scene let alone go on accu­rately to record the full, incredible variety of rich colors of coral reef life forms at night.

The red end of the light spectrum produced by the 3 200K lights is ab­sorbed just as with daylight. The same subtractive filter values are required for the same length water paths. The difference with lights is that we must change filters in the cameras in smaller increments with each 1-ft change in the water path length. This is because, as related to working with ambient daylight, the relatively severe drop-off of the intensity of the artificial lights makes the color changes more obvious. The requirement for filter changes every 12 in. is explained also by the fact that we create a far greater per­centage change of the total usable water path than when we work solely with ambient light, where a 1-ft change in a total water path of 40 to 60 ft is a much smaller percentage change.

To obtain correct colors, the first subtractive filters are required when the camera/light-to-subject distance is 1 ft. The distances we are talking about, by the way, are real distances, not apparent distances as perceived by divers wearing conventional masks. With the Aquacolor cameras, correctly recording the full spectrum of colors in water at night with the Aquacolor lighting system is dependable and relatively simple - provided we keep all illuminated subjects equidistant from the camera and lights.

The only time we work with the 3200K lights in the daytime is where ambient light is photographically insignificant - in deep water, under ledges, or in caves or wrecks, etc. “Photographically insignificant” means the ambient light is no more than 1/16 of the light available to illu­minate the scene. In other words, the lights must raise the illumination in the scene at least four stops. Then we simply use our tungsten film, lights, and subtractive filters exactly as for night filming.

When filmmaking in natural am­bient light through 40 to 60 ft or more of water, Aquacolor subtractive filter technology produces far more color in scenes than we have ever seen achieved with artificial lighting in open water. However, there are always scenes that can be improved with selective key and fill lighting.

Now we have come to the difficult part: creating key and fill lighting underwater in daytime while the Aquacolor camera color corrects the ambi­ent natural light. The only way we know consistently to achieve color-correct pictures this way is to use fill lighting with the same color temperature as the ambient light for any given water path. Then both light sources simultaneously will receive proper color correction from the Aquacolor filters in the camera. Thus we may alter the intensity of light in portions of the scene, but not the color tem­perature of the ambient natural photographic light.

Reflectors would appear to be the simple, logical way to provide the supplemental lighting with color tem­peratures that match the ambient light. Unfortunately, reflectors of sufficient light-gathering capacity in the diffuse light in water too often would be unmanageable in the ceaseless motion of the sea. The logistics and limitations are so obvious we have made no attempts to experiment with reflectors for ambient daylight in water.

We have experimented with two self-contained ni-cad-powered xenon arc underwater light units which we built recently. Without auxiliary lenses the lights are 12.3 times brighter than automobile high-beam headlights. With diffusers to spread the beams uniformly throughout the field of coverage of a 10mm lens, the lights should have a range of 30 in. To the 6000K lights we must add a series of blue conversion filters to produce supplemental key and fill lighting to match the color temperature of water for various water paths. When we proceed with tests with the complementary filter selections, it then will be possible to provide servo-operated, continuously variable conversion filters on any 5600K lights. The servos will be controlled automatically by the Aquacolor camera’s filter selection system.

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“The underwater cinematographer rarely gets a second opportunity to record some of the most unexpected and exciting events in the sea. High-definition TV is making impressive advances, but at this time remains an imperfect hybrid as a video-to-film bridge.”

Aquacolor for Video

Aquacolor film-to-tape transfers have been accomplished with colors so bright and true that transmitted scenes were saturated with color. Contrast is created by showing objects in full color instead of as monochromes. The color contrast accentuates the definition of underwater objects. This increases the amount of detail in each scene, making Aquacolor pictures excellent for tele­vision viewing.

The best film-to-tape transfers were made directly off the Eastman color high-speed negatives. The negative film density range fits within the density range of typical NTSC or PAL systems, so it can be transferred di­rectly from the negative (by reverse polarity). In this manner, the fullest amount of information is transferred to the videotape before the negative density scale is expanded to the greater density spread of the projection print.

Theoretically, projection print film-to-tape transfers are not desirable for Aquacolor pictures. The dynamic range of the video system runs from a minimum peak light density of about 0.3 to a maximum TV black density of roughly 2.4. The relative density range of a positive projection print extends from 0.2 to 4.0. The density scale of the print is not compressible. So when transferring from a projection print, everything within the density range of roughly 2.5 through 4.0 is lost as TV black. This is not to say that projection print transfers necessarily are a handicap for films made in controlled studio lighting situations with lighting ratios of 2:1. But for the uncontrolled lighting situations encountered un­derwater, such density constrictions can result in acute loss of details and colors in shadow areas. For illustra­tion, all one need do is watch any TV newscast and observe what happens to back-lighted subjects shot in sunlight.

Aquacolor technology can color-correct the light for video cameras just as it does for movie cameras. At this time, however, TV producers will achieve superior Aquacolor videotapes if the underwater scenes are recorded on Eastman color high-speed negative film and then transferred directly to tape.

Limitations

The Eastman color negative film tolerates lighting ratios of 4:1 in any given scene. Video tolerates less. Video lighting contrast ratios are not ade­quate to the task of filming by ambient light in the sun and shadow environ­ment of the sea. Working with such restrictive luminance ratios in all but ideal reflective white and sand bottom areas requires the use of fill lights. Otherwise, too many shadow details and colors invariably must be lost as TV black.

A useful generalization is that the human eye handles a lighting contrast range of 1000:1, film of 100:1, and video of 10:1. Working through the dense Aquacolor multiple filter com­binations requires the full camera ex­posure latitude of 7 stops provided by the new Eastman negative film. Video camera exposure latitude may be as little as 2-1/2 stops, with latest state-of-the-art advances that approach 4-1/2 or even 5 stops. Without the full 7-stop latitude, Aquacolor techniques cannot be applied consistently through 40 ft and more of sea water, which is important for professional applications.

There are other shortcomings unique to pure video production in the sea. Video cannot tolerate overexpo­sure the way film can. In video, highlights burn out if only 1/2-stop over acceptable brightness. In video, 30 pictures are recorded each second on electronic camera pickup tubes. Each picture must be blanked out, or switched off, before the next picture can replace the existing one. Total blanking out of each picture (actually comprised of two fields of 1/6o-sec duration each) has not been perfected as yet. So burn-out in highlighted areas is carried over by the electronic signal into subsequent pictures. Stationary burn-out spots are called bloom. If the camera or the high­lighted object moves, the burn-out spot will appear as a comet-tail, as it streams through the scene. The point is, bloom and comet-tail producing situations are exceedingly difficult to avoid in tropical and subtropical underwater filming situations. Sunlight glints off mask face plates, watch crystals, chrome-plated diving equipment, silver-sided fish, etc. And the use of fill lights to complement the low lumi­nance ratio of video is certain to create some back-scatter and flare off particulate matter and objects in ocean water in addition to the sunlight reflections.

Because video engineers usually increase color saturation intentionally, video cameras have not been noted for their ability to record soft, pastel colors. The lovely pastels that hold up so well in Aquacolor negative-to-tape direct transfers probably would not be in the tapes had the underwater scenes been recorded on video instead of film.

The underwater cinematographer rarely gets a second opportunity to record some of the most unexpected and exciting events in the sea. High-definition TV is making impressive advances, but at this time remains an imperfect hybrid as a video-to-film bridge. In the sea, where anything can and often does happen, scenes recorded on film have more application, and perhaps value, than those restricted to tape. Productions originating on film will be available for HDTV when that replaces conventional TV. Current TV-originated productions presently do not have that prospect of being carried over into future HDTV mar­kets. At the rate man’s activities are transforming coastal waters, the colors we record in the next few years may be the last - perhaps giving the films untold value in the not-so-distant future.

It should be noted that movie cameras remain quantum leaps ahead of video cameras in quality image making, simplicity of operation, and reliability. The reliability factor is especially important around salt air and water locations, which often are far removed from repair and maintenance facilities and personnel.

A number of times we have been asked if the white balance of video cameras could be modified to perform the Aquacolor color corrections auto­matically, thus simplifying the cou­pling of color correction to the depth and focus settings. It can be done, but it is not practical. Existing white bal­ance controls cannot cover the range of color temperatures that we encounter underwater. Also, underwater we work in blue/green light. Video cameras are set up to deal with color temperatures ranging from daylight to tungsten light. Specialized cameras modified to deal with underwater light would not be usable out of the water, and still would lack the lighting contrast range of film, so many details would be lost.

Enormous efforts are being made to overcome the limitations of video cameras, and with truly dramatic ef~ fect. Outstanding examples are Pan­avision’s Panacam Reflex and Ikegami's EC-35 electronic cinematography cameras. When electronic cinematography passes through its present era of growing pains, it will begin expanding cinematographers’ horizons the way telescopes expand the universe. But that day is not yet with us. For professional Aquacolor picture-making, film continues to offer significant advantages over the present limitations of pure video production.

Future Developments

The original plan was to develop the Aquacolor camera systems in five steps. The first three have been com­pleted: metering system, aperture control, and Aquacolor filters.

The films being made with the ex­perimental cameras have proven the Aquacolor system. Preliminary work has begun to produce the first prototype 16mm Arri/Aquacolor camera system with auxiliary video viewfinders, recorders, and monitors. The system is being designed to work with every 16 and Super 16 SR Arriflex camera. When these prototypes are successfully launched, work should begin on theater-format Arris and then on step number four.

Step four will be an automatic filter selection to replace the present manual system. Step five will be electronic in­tensification of light in full color, with less than 10% resolution loss. The invention will be used first with video assist to provide 5-in, color monitors for improved viewfinding on the Aquacolor cameras. Then the elec­tronic intensification will be utilized in front of the lens. Aquacolor calculations indicate that it will be possible to fully color-correct in ambient light through more than 100 ft of ocean water.

Investment for the Future

It is hoped that the films produced by the Aquacolor camera systems can show people the overwhelming beauty of the sea, so they may identify with it in more personal and positive ways. The films can help audiences to better comprehend the importance of saving life in the sea, now threatened by the excesses of civilization. For if people do not act soon with wisdom and responsibility, there may be only dead seas to film. Then what purpose underwater color films?

Appendix

References

I. Marston Bates, The Forest and the Sea, New York: Signet Science Library Books, 1964, p. 55.

2. H. Schenek, Jr. and H. Kendall, Underwater Pho­tography, illus. by John E. Johnson, Cornell Mari­time Press, Cambridge, MD, 1957, p.70.

3 lbid.,p.78



Bibliography



SMPTE, Elements of Color in Professional Motion Pictures, New York: Society of Motion Picture and Television Engineers, 1957.

Myers, HoIm and MeAlliater, Handbook of Ocean and Underwater Engineering, New York McGraw-Hill Book Co., 1969.

SMPTE, Technologies in the Laboratory Handling of Motion Picture and Other Long Films, Santa Monica, CA: Society of Motion Picture and Tele­vision Engineers, 1971.

Lawrence E. Mertens, In- Water Photography, New York: Wiley-lnterscience, 1970.

ASC. American Cinematographer Manual (First through Fifth Editions), Hollywood, CA: American society of Cinematographers, 1969-1980.

F. Schulke, Underwater Photography for Everyone, Englewood Cliffs, NJ: Prentice-Hall, Inc., 1978.

I. Mascelli, Mascelli’s Cine Workbook, Hollywood, CA: Cine/Grafic Publications, 1973.

A. wiia~~n, Cinema Workshop, Hollywood. CA: AS.C. Holding Corp., 1983. H. Frey and P. Tzimoulis, Camera Below, New York: Association Press, 1968.

R. Church, Photography Underwater, La Jolla, CA: Ron Church Prod~ctions, 1971.

U.S. Navy Department, U.S. Navy Diving Manual, Washington, D.C.: U.S. Government Printing Of­fice, 1965.

B. Slosky and A. Walker, Guide to the Underwater, New York: Sterling Publishing Co., Inc., 1966.

Reed’s Nautical Almanac and Coast Pilot, American East-Coast Editions, London: Thomas Reed Pub­lications Ltd., annual. Kodak Color Dataguide, Rochester, NY: Eastman KodakCo.. 1971.

Kodak Professional Photoguide, Rochester, NY: Eastman Kodak Co., 1975.

Kodak Pamphlet No. P-124, Bibliography on Under­water Photography and Photogrammetry, Roch­ester, NY: Eastman Kodak Co., 1968.

Kodak Publication No. B-3, Kodak Filters for Scien­tific and Technical Uses. Rochester, NY: Eastman Kodak Co., 1970.

Kodak Publication No. H-I, Selection and Use of Kodak and Eastman Motion Picture Films, Rochester, NY: Eastman Kodak Co., 1976.

Kodak Publication No. E-77, Kodak Color Films for Professional Use, Rochester, NY: Eastman Kodak Co., 8 Editions.

Kodak Publication No. E-74, Color as Seen and Pho­tographed, Rochester, NY: Eastman Kodak Co., 1962.

R. C. Seblin, F. R. Reinking, S. W. Spakowsky, D. L. Clifford, G. L. Whittier, and W. A. Szafranski, “Eastman Color Negative Film 7291,”SMPTEJ. 92: 1302-1309, December 1983. W. E. Green, “Photography Underwater,” The Ex­plorer, 18: 4-8, The Cleveland Museum of Natural History, Spring, 1976.

W. M. Stephens, “Sophisticated Underwater Cameras to Bring Depths Into Sharp Focus,” Oceanology International, pp. 37-40, May/June 1967.

W. v. Burt and G. F. Beardsley, “Underwater Optical Measurements,” Oceanology International, pp. 35-39, May/June 1969.

D. E. Williamson, M.D., “Underwater vision,” Skin Diver, pp. 24-26, 66, Sept. 1967. B. DeCourt and S. DeCourt, “Expand Your Horizons With a Corrective Underwater Lens System,” Skin Diver, pp. 12-14, 68-69, Feb. 1969.

G. T. McNeil, “The Dome Port in Underwater Pho­tography,” Skin Diver, pp. 40-43,67, Oct. 1970. S. Jordan, “Selective Color Attenuation varies for Several Reasons,” Skin Diver, pp. 6 1-62, 76-77, Jan. 1971.

G. Fishbach, “zonal Color Exposure Control,” Pho­toGraphic, pp. 71-74, May 1974. H. Fry, “Underwater Lighting Considerations,” In­dustrial Photography, pp. 18-19, 42,48-49, June 1972.

J. Birns, “Underwater Lights,” Oceanology Interna­tional. pp. 33-35, Feb. 1970. i. w. Harford, “Underwater Lighting: Current Capabilities,” Industrial Photography, pp. 23, 32, 34, 38-41, June 1971.

Author unknown. “Comparing Carbon Arc, Xenon, Selected Incandescent and Mesal-Halogen Lamps,” American Cinematographer, pp. 1148, 1184, 1219, Oct. 1975.

D. w. Samuelson, “The Breakthrough to Flicker-Free H Ml Lighting,” American Cinematographer, pp. 1186-1189, 1200-1201,Oct. 1975. A. Bodkins, “An Improved Daylight PAR Lighting System,” American Cinematographer, pp.430-431, 474, April 1976.

P. vlahos, “Daylight Filters: A Color Specification and Method of Measurement,” AMPTP Research Center Bulletin,Jan. 15, 1971. Thorn Lighting Ltd., “Thorn Lighting Introduces Hot Restrike CSI Lamps,” American Cinematographer, pp. 1040, 1084.

E. B. Noffsinger, “Image Evaluation and Criteria and Applications,” SPIE J., pp. 95-103, March 1971.

P. Parker, “The SMPTE Television Conference,” In­ternational Broadcast Engineer, 15: 79-85, May 1984.

K. Richter, “There’s More to ‘Clear Pictures’ than Meets the Eye!”, American Cinematographer, pp. 974-975, 986-987, 990-991, 1033-1038, Oct. 1978.

A. Gornick, Jr. “Blunting Neptune’s Trident,” Inter­national Photographer, pp. 10-11, 29-31, Sept.! Oct. 1982.

J. Birns, “Lighting for the New Dramaties ... Un­derwater,” International Photographer, pp. 12-13, 29, Sept/Oct. 1982.

P. Parker, “NAB ‘84,” International Broadcast En­gineer, 15: 40-48, July 1984. L. J. Roberts, Electronic Cinematography video Cameras,” International Photographer, pp. 10, 34, July 1983. J. Gainshorough, “Walt Deas, Underwater Camera­man, ‘Eyepiece, 5: 38, 40, Jan/Feb. 1984.

SMPTE Journal, March 1985