TAKE A LOOK AT THE PHOTOGRAPH that accompanies this article. When I shared this image at a recent meeting of the San Diego Underwater Photographic Society, one of the newer club members asked, “How did you manage to properly expose the sponge and blue water that surrounds the diver?” She explained that in a similar scenario, the water in her photograph was almost solid black and she couldn’t even see the diver in her frame. She only saw a small white dot from the light the diver was holding.
The question is relatively simple to answer but over the years I have seen photographers complicate the process because they don’t understand that the exposure process needs to begin by taking a light meter reading on the blue water, even though the water occupies a very small portion of the composed frame.
For this type of shot, one in which you are trying to properly expose a small section of sunlit water in your frame, I recommend using the manual exposure mode. At the very least, you want to understand how to get the correct exposure in the manual mode so that you understand what you are asking your camera system to do if you use any kind of “automatic” exposure mode.
There are several ways to go about getting the proper exposure of the blue water. (1) You could swim to the opening and take a light meter reading on the water. Of course, that is time consuming and the swimming and exhalation bubbles can stir up backscatter-producing particulate. (2) You could use spot metering and very carefully aim your light meter at the blue water. (3) You could take a series of photographs before the diver gets into position (thus blocking too much water) and check the exposure of the blue water on the camera’s LCD screen, or with your histogram, using the camera’s playback mode. (4) Or, as I did in this case, you could ascend a few feet, look over the top of the ledge, hold your camera at an angle that allows you to take a light meter reading on the water behind the opening.
In all of these scenarios, all I am suggesting is that you make sure to take your light meter reading on the blue water and that you make sure you are not taking the reading on the diver, the dark sides of the cave or on any other element in the frame.
Used properly, your light meter reading establishes your camera system’s exposure settings (f/stop, shutter speed and ISO). Do not change them. These are the settings you will be working with.
Now let’s turn our attention to the sponge. The exposure challenge is to adjust your strobe power when composing your shot after you have taken your light meter reading and your f/stop, shutter speed and ISO are set. By composing your frame, you establish your strobe-to-subject distance and that should help you determine the correct power setting for your strobe.
In essence, what you want to do in this shooting scenario is expose the water and sponge exactly the same way you would if the diver and cave were not in the frame. That’s the way to keep the exposure process from getting more complicated than it needs to be.