PROF. HAROLD E. EDGERTON*

Massachusetts Institute of Technology

Cambridge, Mass.

Supplementary Lighting in

Underwater Photography

Sound will provide the principal way by whichmen and instruments will do precise navigationin the sea.

ABSTRACT: Photography in the sea, particularly the deep sea, requires a lightsource near the camera because daylight from the surface does not penetrate.~onttnuous sources of light require an energy source which may be large andmvolved, and are, therefore, only used for visual observation, for motion-picturephot~graphy, and f~r television. Flash lighting is almost universally employedfor nngle-puture sttll photography as ample energy is contained in a small bat-tery to expose thousands of photographs. Calculations are shown to aid in thedesign of an illumination system that allows for the absorption and scatteringeffects of sea water.

SUPPLEMENTARY LIGHTING IN THE SEA

H UMAN OB~ERVATIONS AND photographyat depth In the sea must be accomplishedwith auxiliary lighting as sunlight is rapidlyabsorbed with depth. Even at 30 meters belowthe surface, sunlight is very feeble. A sourceof light should be taken into the sea whenworking at almost any depth.

If close to the surface and below a ship, anelectrical cable can be used for power tooperate an over-vol ted tungsten lamp. Cous-teau has used this system most effectively inhis remarkable award winning motion pic-tures The Silent World and World WithoutSun. He uses tungsten lamps that are over-vol ted momentarily during the operation ofthe motion picture camera. The diver-photog-rapher signals the engine room of the R/VCalypso by means of a buzzer when the fullpower of the lamp is required for photog-raphy. Cousteau uses a daylight type ofcolor film with tungsten illumination. Thecolor balance of the camera-light is correctedat one distance because the water absorbs the

* Presented at the Annual Convention of theAmerican Society of Photogrammetry, Washing-ton, D. c., :vIarch 1967 as one of several paperson underwater photography, all contained in thisissue.

red light more than the blue. A yellow pictureresults for closer distances than this and ablue-green one for further. The casu~l audi-ence attending an underwater movie is notconscious of these subtle color changes asthey are so occupied by watching the actionon the screen.

Strobe and flash lamp lighting equipmentare of the greatest importance in the sea forstill photography, because the illuminationfrom the sun ceases to be useful at shallowdepths due to the absorption and scattering inthe water. It is always night or bad weather orfoggy when one goes below the surface of thesea. Supplementary lighting equipment is anessential item whenever still cameras are usedin the sea, not only to furnish light, but also toovercome the color unbalance, and unevenlighting from light transmitted from the sur-face.

The expendable flash lamp is of great usefor underwater photography, because of thelarge quantity of light that is available fromthe chemical burning of the oxygen and metalfoil. A slow shutter speed 0/25 sec.) is de-sired so that as much light as possible can beused. As with the motion pictures, Cousteauand others use the expendable flash lamp at adistance of 3 meters plus from the subject and

906

SUPPLEMENTARY LIGHTING IN UNDERWATER PHOTOGRAPHY 907

depend on the selective absorption of thewater to reduce the red light so that thebalance is correct for daylight color film. Adaylight blue Aash lamp can be used at closerdistances in water, for example, less thanabou t 2 meters.

Electronic Aash is an advantage under-water if many photographs are taken becausethe diver does not need to replace the lamp ashe does with the expendable Aash lamp. An-other important property of an electronicAash source for underwater photography is itsability to produce thousands of Aashes effi-ciently from a small electrical battery. Thus,the inability to control exactly where andwhen a photograph is to be made underwaterby suspended cameras can be compensatedpartly by taking many thousands of photos.

The photographer of underwater subjects,especially deep-sea, seldom has the artisticfreedom of his above-water brother. Most ofthe time the underwater camera operator isshooting blind with a camera by some sort ofremote control. It is possible to go with thecamera in a bathyscaphe or diving saucer as aview finder, but this is a luxury arrangementwhich is not available for most routine deep-sea photography assignments. In some cases atelevision camera can be used as a remoteview finder to aid the photographer to selectthe right moment to release the shu tter.

Unfortunately, one cannot see or photo-graph greater than approxi mately 30 metersfrom the camera, even in the clearest of oceanwater. A more practical limit for photographyseems to be 10 or 15 meters in mid-ocean atthe bottom where conditions are good. Be-yond 15 meters a haze absorbs light anddestroys the photographic image. Many at-tempts have been made to overcome theoptical limitations by selecting the mostfavorable wave length, but to my knowledgeno spectacular results have been attained.One may conclude that the camera shouldhave a wide-angle lens which should be keptas close as possible to the subject, so thatoptical effects from the water are minimized.Likewise, the ligh ts should be separated fromthe camera and closer to the su bject than thecamera in order to prevent back scattering,absorption, and to give shadows and model-ing.

Photography of the bottom of the ocean isof great importance. To cover a square milewith 10-by-10-meter photographs will requiresome 29,000 photographs if no photo-overlapis obtained. This is a lot of photos to process,study, and position. Accurate bottom map-ping by photography is a big task. There are

-1i(2.

many square miles in the ocean! And thenthere is also the space between the bottomand the surface to be explored.

A few practical systems of underwaterphotographic equipment will now be de-scribed and some examples will be shown.Figure 1 shows a typical arrangement of twocameras (stereo pair), an electronic Aash unit,and a pinger on a metal rack (Unistrut sys-tem). Dr. J. B. Hersey, formerly with \\ToodsHole Oceanographic Institute, and now at theOffice of Naval Research, says "A singlecamera is only one half of a stereo camera sys-tem!" His experience wi th stereo has im-pressed him with the added information thatthe stereo presentation produces, and he in-sists on a two-camera stereo pair. He alsowan ts color in at least one of the stereo cam-eras, because it gives added information.

Another underwater camera arrangementused on W.H.O.r. ships is shown in Figure 2.Note that the strobe is closer to the bottomand off the axis of the camera as this position-ing tends to red uce the back scatter from thestrobe. A si milar arrangemen t with as manyas three cameras and two 200-watt-secondstrobes have been used to obtain photographswith the cameras at 15 meters above thebottom in clear ocean water. The Unistrutsystem enables a camera user to modify or

908 PHOTOGRAMMETRTC ENGI EERING

change his camera-lamp arrangement quicklyto suit his whims.

An improved camera system, with 400 footreels of film instead of 100, has been devel-oped in response to a request from 'vV.H.O.I.and others who wish to take many photos inthe sea.

The recen t discovery of very large sharks atgreat depths (1100 fathoms) off San ClementeIsland, California was made with a camerasystem conceived by Prof. John D. Isaacs(Scripps Institution of Oceanography). Thecamera-flash lamp system is thrown over-board and allowed to stay on the bottom un tila time delay release mechanism permi ts thecamera to float to the surface for retrieval.Rare bottom fish have been photographed aswell as a large shark at a bait box on the bot-tom.

LIGHT REQUIREMENTS

Below a few hundred feet of depth in waterdaylight is inappreciable and auxiliary light-ing is required. A lamp on or near a camera isneeded to produce the following beam-candela-seconds (BCPS) to expose a photo-graph.

c(BCPS) = D2A 2 - l'2D

S

where

D = lamp-subject distance and camera-sub-ject distance

A = camera lens apertures = ASA fil m speedc = a constant 15 to 25, when D is in feet

a constant 162 to 270, when D is inmeters

a = absorption co-efficient of the water innatural log units (e=2.73)

If aD = 1 the light (BCPS) must be increasedby 2.732 , or 7.5, compared to air use. At twoattenuation lengths the factor is 55. Beyondthis distance the ligh t losses are so great thatphotography is almost impossible, especiallydue to the image loss in the low-contrastphotograph. No convenien t easy-to-use meteris available to measure the factor, ea2D , whichcould be called the water factor.

The absorption coefficient depends uponthe wave length (color) of the light with the

largest value in the red. Duntleyl gives in-formation for distilled water (Table 1). It isobserved that the red light will be absorbedmuch more than the green or blue with dis-tance, thus disturbing the color balance.

Suspended particles in the water of theocean absorb and scatter the light so that theattenuation length is much shorter than theabove information for distilled water.

CAMERA CONTROL

A very practical problem of photography inthe sea is measurement and control of theheight of the camera over the bottom whilephotographs are being made. A camera forexample, must be held accurately at someselected height, such as 10 meters from thebottom. There are at least four ways to dothis.

1. The trigger2 method where a shutteroperating device, usually a switch, hangs be-low the camera. This bottom-activated elec-trical swi tch causes operation of the camerawhen it is at the desired height. After the ex-posure is made the camera is raised in prep-aration for the next operation.

2. The use of a pinger3 sound source on thecamera which enables the operator on the shipto know at all times where his camera islocated above the bottom. A pinger sends outa short powerful pulse of underwater sound atregular one second intervals. One sound wavegoes directly to the surface from the pinger,and another goes down to the bottom of thesea, is reflected, and then arrives at a latertime at the surface. The operator on the shipmeasures this time delay between the twosignals, and thereby knows where his camerais positioned as the velocity of sound in wateris known to be about 5,000 feet per second.

3. The sled system of Capt. Jacques Cous-teall. His device, a special sled which carriesthe camera and strobe, has the ability to rightitself regardless of how it is dragged across thebottom by a strong cable from the ship.

The sled, or troika as Cousteau calls it, is anideal platform for a deep sea camera. Thelamps and cameras are carefully placed be-hind the heavy metal parts of the sled toreduce the probability of damage as the sledgoes through rough areas on the bottom of the

Color Blue

TABLE 1

Green Red

Wave length, mlJ.l/a (In) meters

40013

44022

48028

52025

56019

6005.1

6503.3

7001.7

SlJPPLEME TTARY LlGHTI TG IN UNDERWATER PHOTOGRAPHY 909

sea. Cousteau is always careful to make a de-tailed sonar study of the area he plans to draghis sled over, also observing winds and tides.Then lowering the device to the bottom, hebegins traversing over the area of interest.

What if the sled becomes wedged into atough spot and becomes an anchor? Cousteaupartially solves this problem with a doublecable attachment method. The main cable isfirmly attached to the stern of the sled. Aweaker cable ties the main cable to the bow.If the sled is stuck, a powerful vertical pullwill break the weak connection and the sledwill upend, hopefully releasing itself from thebottom attachmen t.

Cousteau once dragged his sleds over themid-Atlantic rift mountains and obtainedsome remarkable photographs. One of theseappears as an illustration in his book TheLiving Sea'. I urge you to take a look at thatmoon-like scene and wonder how in the worldhis sled could go in such a rough place withouttrouble. Incidentally, one of his sleds is still onthe bottom, about halfway to Europe. If youwant this sled with its movie camera andstrobe for a souvenir I am sure that Cousteauwill give it to you if you find it. Please notethe location, the sled is halfway betweenMonaco and New York, possibly north of thedirect line by some 500 or a thousand miles!

4. The captive vehicle5 method. One systemuses a TV camera on a tethered submersiblewith a cable to the master ship. A monitorscreen permits the operator on the ship tocontrol the submersible into the desired pat-tern. Then when the subject is in Yiew, thephotographic equipment is turned on to ob-tain high quality photographs for measure-men t or record purposes.

An ambitious project was undertaken in1961 on the continental shelf off l\ewfound-land to photograph submarine cables. Asstated by G. R. Leopold in his Bell TelephoneLaboratory report (File f O. 34912-16), "Thepurpose of the investigation was to examinethe cables and the ocean bottom at firsthandand to seek out possible physical explanationsfor our apparent vulnerability to trawlerbreaks in the area."

This vehicle, with a controlled buoyancyframe using electrical propulsion, was madeby the Vare Industries. An electric cablejoined it to the mother ship, the Polar Star.On board the vehicle was a television screento record the action below, and the necessarycontrols to guide the vehicle to follow thecable once it was found.

A deep-sea 35-m m. camera and a 100-watt-second xenon flash lamp were mounted near

the TV camera tube as a remote view finder.An operator watching the TV screen couldtake photographs whenever he desired bypressing a push button.

Another very difficult but successful deep-sea effort was the photography of theThresher site, some 200 miles east of Boston,in 8,500 feet of water. The ill-fated Th.resherwas a nuclear powered submarine that sunkduring her deep diving tests in April, 1963.Many groups worked on the photographyeffort. Worzel of the Lamont Geological Ob-servatory, Columbia University, while aboardthe Robert D. Conrad made many photographswith a Thorndike Camera of the bottom con-tact type. Hersey used the pinger system onseveral Edgerton, Germerhausen & Griercameras, together with four widely spacedhydrophones while aboard the Atlantis II,for camera location information. Buchananand Patterson, Office of Naval Research, usedcameras with remote surface control. Thecameras were started from the surface when amagnetometer near the camera showed thepresence of iron. Some 40,000 photos weremade within 1,000 feet of the wreck. Fromthese a photomosaic was made. Part of theThresher wreck was photographed with thenumber of the submarine clearly visible.

The bathyscaphe Trieste (remodeled andcalled Trieste II) made eight dives at theThresher si teo Photographs were made andalso a clearly marked piece of pipe was re-trieved from the bottom.

Excellent photographs of the H-bomb thatwas lost and recovered off Spain were madefrom the Alvin and other underwater vehiclesduring the past year.

There are many cameras at the bottom ofthe sea. I personally know of one stereo pairthat is full of exposed pictures, probably thebest that I have ever made. This loss was ex-perienced at a spot on the north wall of thePuerto Rico Trench at 20°07' North, 66°30'\,Vest. '0le were pulling the gear up with thewinch after the photo run. Suddenly the cableparted and down it wen t. There are thou-sands of feet of cable on top of the camera.

I thought it would be worth a retrievaleffort, so the next year I was at the same spotwith an improvised hook and had the use ofthe ship for an all night dragging search. Noluck. Perhaps we snagged the cable but itslipped free. \Ve were probably at the wrongspot due to navigation errors. Better fishingnext time! If anyone finds the camera systemplease remember that the film should bedeveloped. One camera has Plus X film, theother has super Ektachrome color film.

910 PHOTOGRAMMETRIC ENGINEERl NG

POSITIONING AND NAVIGATION

Bottom photography usually is uneventful,showing many miles of desert-like sediment.Therefore, it is not too important to knowexact positions. If one expects to photographthe identical area for a second ti me, it will bevery difficult for two reasons: (1) the exactshi p' s posi tion is not known; and (2) tides andcurrents displace the camera in an unknownmanner even if the ship is held directly abovethe target. Some method of bottom navigationis required if the camera is to be brought backto an identical bottom area.

One way to locate a spot on the bottom is toanchor a buoy. The position of the buoy, withrespect to the anchor position, will depend onthe water currents and their effects on thefloat. Tight cables from large buoys to a largeanchor tend to minimize the positional error.

A second and more involved method is asonar transponder on the bottom which sendsa ping when commanded. Let us call this asound-house, as con trasted to a lighthouse usedin surface navigation. \iVhenever one sends asound signal from the surface, or from apinger on a camera, he will receive an echoresponse at a delay corresponding to the dis-tances involved. Thus, he can measure twodistances, one to the bottom, and a second tothe sound-house.

A transponder sound-house receives soundpulses from the sonar on the ship and returnsa re-enforced echo which is also recorded onthe sonar receiver. A series of signals will ap-pear on the chart from the sound-house. Theship and sound-house are at their closest posi-tion when the signal is received at the earliesttime on the recorder chart. A second pass canthen be made from another direction to ob-tain further information.

If two sound-houses are used, two positionscan be located on a chart where the shipmight be located. With three sound-houses,there is no ambiguity in the ship's position.The positioning and navigation problem isexactly the same as the surface navigationalfix where information from three known light-houses is used. A lighthouse gives an angle; incontrast, a sound-house gives an echo delaytime which is proportional to distance as thevelocity of sound in water is almost a con-stant. The bottom navigation problem is moredifficult than the surface navigation problembecause of the added complication of waterdepth. The submerged water craft and anaircraft have exactly the same problem ofnavigation in a three-dimensional medium.Several problems may be experienced in the

initial installation of the sound-houses; butonce they are in place, an accurate survey canbe made and the ship should be able to gorepeatedly to the same pinpoint spot in thesea.

N ow the camera, or other devices, can alsobe accurately located by the use of a pinger onthe object lowered. The pulses from thepinger will give the operator on the ship theusual camera-to-bottom distance. At thesametime, the pulses from the camera willstimulate the transponder sound-houses andthey in turn will send additional signals to theship. These signals enable the operator toknow where his camera is located with respectto the target, if the position of the target isknown with respect to the sound-houses.Then the remaining job is the manipulation ofthe ship so that the camera photographs thedesired subject. This requires skill. The samesonar procedure can be used with the bathy-scaphe, with the additional feature that ahuman observer can take over the controlswhen the subject comes into view. Also, theuse of a side-looking6 sonar can be very help-ful if the target sticks out of the bottom, oncethe bathyscaphe has been put into the desiredarea.

The sound-house transponder can be usedas a marker. For example, a submarine couldtake one along on her dives with the provisionfor dropping it at the main center of interest.In this way the sub can go back to the identi-cal spot for another effort to photograph orsearch.

In conclusion, it seems evident that soundwill be the principal way in which men andinstruments can do precise navigation in thesea. Both light and radio are not effective forlarge distances underwater because of absorp-tion. Sound will be effective to several mileswhereas photography is only effective to 30meters under ideal conditions. However, thetwo methods are used together for obtaininginformation about the bottom of the sea; andsound, of short pulse length6, can furthermoregive important information to the geologyand archaeology of the sediments below thebottom.

REFERENCES

1. Duntley, S. Q.! "Light in the sea," Journat ofthe Opttcal Soctety of America, 53, (2), pp. 214-233, February 1963 (This is a review article withmany references).Tyler, J. E., W. H. Richardson, and R. \71/.Holmes, "Method for Obtaining the OpticalProperties ?f Large Bodies of Water," Jomnalof Geophysual Research, 64, (6), pp. 667-73,June 1959.

SUPPLE.IENTARY LIGHTING IN UNDERWATER PHOTOGRAPHY 911

Preisendorfer, R. W., "Divergence of the lightfield in optical media," Scripps Institute ofOceanography, Univ. Calif., Ref. 58-41, p. 16,1957.

2. Ewing, M., A. Vine, and J. L. \\'orzel, "Photog-raphy of the ocean bottom," J. Opt. Soc. Am.. ,36, (6), pp. 307-321, June 1946Edgerton, H. E., and R. T. Troutner, "Deep seaincandescent lamps," Under Sea Technology,pp. 21-26, April 1966Edgerton, H. E., and J. R. Killian, Jr., "Flash,seeing the unseen," Branford Press, Newton,Mass. (2nd Edition) 1954

3. Edgerton, H. E., and J. Y. Cousteau, " nder-water camera positioning by onar," Rev. Sci.Inst., 30, (12), pp. 1125-26, December 1959Edgerton, H. E., " nderwater pinpoint pho-tography," SPIE Technical Symposium LosAngeles, California, AUgllst 8, 1963 (Journal ofthe SPIE, pp. 3-5, Oct./Nov. 1963)Edgerton, H. E., " Underwater photographywith strobe lighting," and "Sound in the sea,"

SPIE Convention, Santa Barbara, Cal. Oct.1966.Nalwalk, A. J., J. B. Hersey, ]. S. Reitzel &H. E. Edgerton, "Improved Techniques of deep-sea rock-dredging," Deep-Sea Research, pp. 301-302, Aug./Sept. 1961

4. Cousteau, J. Y., "The Living Sea," Harper &Row, p. 239, 1963

5. Leopold, G. R., Bell Telephone Lab Report (FileNo. 34912-16)

6. Yules, J. A., and H. E. Edgerton, "Bottomsonar search techniques," Undersea Technotogy,pp. 29-32, November 1964Edgerton, H. E., and G. G. Hayward, "The'boomer' sonar source for seismic profiling,"Journal Geophysical Research, 69, (14), pp. 3033-42, July 15,1964

7. Hersey, J. B., "Sound Reflections In and UnderOceans," Physics Today, 18, (II), pp. 17-24,November 1965

8. Edgerton, H. E., "Exploring the sea withsonar," Discovery, pp. 40-45, September 1966

(Continued from page 905)

color control in printing far more accuratethan any combination of filters with trans-parency film can provide in the rapidly chang-ing undersea conditions.

Left until last in this report is the mostversatile of color-control tools when usedskillfully-artificial light. Flash bulbs (bothclear and blue), photoflood lamps, quartziodide lamps, and electronic flash are excel-lent agents of color restoration. Blue flashbulbs and electronic flash approximate thecolor temperatures of daylight. For shortlight-to-subject distances they bring out colorwell. Longer distances reduce their effective-ness. An ideal ligh t-to-su bject distance of 5 to6 feet gives a subtle, pleasing effect of partialrestoration but does not overpower the blueunderwater feeling. Flash weak enough to bea fill-in and not a main light source is espe-cially effective at this distance.

Clear flash bulbs, or incandescent lampsburning with a warm light, are effective colorcontrollers at greater distances than colderdaylight-balanced light sources. The blue ofthe water acts as a normalizing filter when thelights are used with a daylight film instead ofthe tungsten film for which they were de-signed. vVhen too close to the subject, how-ever, the underwater effect can be lost.

Underwater photography is growing out ofits adolescence and equipment is becomingmore sophisticated. Some day underwaterscenics will show subtle color nuances underthe grey-blue mantle, and underwater close-ups will modify the fiery reds and mustardyellows of coral in back of startlingly unreal-looking fish to give a more genuine feeling forthe fish's watery environment.

I should like to see the twilight world ofunderwater penetrated but not overpowered.