by Jim Zuckerman
I encountered one of the most unusual and challenging exposure situations yesterday when I visited the beautiful world-class aquarium in Chattanooga, Tennessee. There are several cylindrical displays of moon jellyfish that are dazzling in their beauty and grace. They are illuminated with lights that keep changing colors, and the lighting is very, very dark. Even at 1600 ISO and f/2.5 I was getting black pictures with virtually no detail.
The only possibility of recording a usable image was with flash. But the Lucite cylinders made it impossible to use on-camera flash because of the reflection. In addition, front lighting wouldn’t show the diaphanous, ever-changing forms of these remarkable creatures. Side lighting wouldn’t do the trick, either. Only direct backlighting would make the animal glow from within and define the delicate internal structures against the dark water.
There were major challenges, though. The tank was about six feet in diameter. I always carry a connecting cable from camera to flash that allows the use of off-camera flash, but it wasn’t long enough. I couldn’t use a slave system because if the flash that was held behind the moon jellyfish could see the on-camera main flash, the latter would also be reflected in the Lucite cylinder. I didn’t have any other flash equipment with me to set up a radio trigger, so I only had one option.
I had my wife hold my Canon 580 on the opposite side of the tank. I used a one second exposure at f/22, and in the dark room this gave her enough time to trigger the flash manually. I counted one, two, three and then I pressed the shutter button and my wife triggered the flash during the one-second window. The room and the exhibit were dark enough so no extraneous ambient light affected the exposure.
I’ve written two books on exposure, and I’ve experimented with special effects with flash photography for 35 years. But in this situation, I had no idea what the exposure should be. There was no way to take a light reading, even with a flash meter, and no way to judge the exposure from experience because I had never done this before. As the floating jellyfish changed the angle of their bodies relative to my Canon 1Ds Mark II – which altered the amount of tissue, and therefore density, between the flash and me – I took several pictures. Fortunately, the immediate feedback of digital technology allowed me to see what was going on. The moon jellies were extremely thin – it was almost like shooting through cloudy cellophane – which meant that it was like I was shooting straight into my flash. The water itself absorbed light, but still the flash was blindingly bright.
After seeing the overexposed images I was getting, I set the ISO on 100, used ETTL mode on the flash, and reduced the output by minus one f/stop. I used f/22 on my 50mm macro lens to make the exposure you see here. The small lens aperture also gave me the depth of field I needed in this situation where focus was critical. I focused using manual focus mode because the autofocus was basically useless in the extreme low light of the tank. Too, the filmy nature of the moon jellyfish didn’t provide a clearly definable surface with enough contrast for the autofocus to function correctly.
The illumination you are seeing is the flash coming right through the jellyfish. My wife was standing about five or six feet behind it.
I used Photoshop to intensify the colors somewhat, but otherwise this is completely unmanipulated.
