COLOR/EXPOSURE CONTROL by Herb Gruenhagen

What is color? Color is the way we perceive differing energy wavelengths of light reflecting off an object. What we call white is the combination of all wavelengths at once; when white light hits an object, the object may absorb some of the wavelengths and reflect others. If all the wavelengths reflect, we see the object as white. If none of the wavelengths reflect, we see the object as black. If some wavelengths reflect and others don't, we will see a color. The color is determined by the wavelengths that reflect off an object.

Water affects the amount of light available because water absorbs the different wavelengths of light at different depths. All the red colors are gone at about 15 feet, so you can understand that underwater color photography depends on a good strobe light or lights. The farther light travels through the water, the more color loss you will experience.

Color underwater photography really depends on the use of good lighting control via your strobe light. This doesn't mean that if you don't have a strobe that you can't take pictures underwater. A wide-angle photographer takes advantage of clear water and available light for the most part and maybe a little fill flash to fill in the details.

The quantity of light that reaches the film or digital chip is called exposure. Along with focus and composition, exposure is one of the basic elements of photography. The photographer can control the exposure using 4 techniques. One is to use the amount of light that is available. Shooting up really helps to expose a subject, especially kelp since it eats light for breakfast.

 The second way is to change film speeds. I really like 100ASA film because it is twice as fast as 50ASA and I have less exposure problems. But, you can compensate for the slow film by using one or both of the other two techniques, that is, either opening up your aperture or changing your shutter speed.

All this is well and good, but how do I find the proper exposure? Some of you will use automatic exposure control with TTL light systems. TTL works for most lighting situations, but the camera light meter can be fooled all too easily underwater. If a large stingray flies overhead with its shiny white undersides between you and the surface, the camera light meter may think there is more light then there really is and shut down your strobes and render the surrounding water underexposed. Underwater photography is really a little science and some guesswork too. F/8 AND BE THERE may help with your next great white shark encounter. This means to set your camera aperture to F8 and bracket one way or the other to get that shot. Experience and lots of practice is what really counts. Shooting lots of rolls of film in the same lighting situation really helps knowing what exposure to use and what works for your camera system. Practicing in a pool has also proved helpful, especially if you have changed some equipment, like strobes lights, etc.

Good luck in the September COLOR competition, where you will be tested not only on good image color, but also on proper exposure and sharp focus.