Real Life Experience - Manual Exposure and the Digital Rebel
Page 13

Green Moray Eel
On a trip to the Bahamas on the Nekton Rorqual, I shot my Nikon D100 while my friend Robin Reed shot a Canon Digital Rebel. I learned some really great lessons about shooting with the Rebel. I carried many of these lessons over to my shooting with my D100. This is the first time that Robin shot an SLR underwater. I really thought that she would have a hard time making the transition from a Nikonos rangefinder type camera to a housed SLR. I was really wrong. She really loved the whole SLR experience.
Shooting Modes - Aperture Priority or Manual?
With my D100, I can shoot in Aperture Priority. This is what happens. If I set the camera to Aperture Priority and connect an underwater flash (Ikelite Substrobe 200), the camera will limit itself to shutter speeds between 1/60th and 1/180th of a second. This is interesting since the camera doesn't seem to know that a flash is attached. When I look at the EXIF info for each shot, it shows that "NO FLASH" was connected. Somehow, it still fires and locks in a shutter speed range. This is a Win-Win situation. If the lighting conditions change with a lot of backlighting, the shutter speed will get faster. THIS DOES NOT HAPPEN WITH THE DIGITAL REBEL! Here is an example of what happens with my D100.

ISO 200, f13 at 1/60th second
Aperture Priority

ISO 200, f13 at 1/180th second
Aperture Priority

In both examples above, I shot in Aperture Priority. Both photos were taken at within fifteen minutes of each other at the same dive location. In the left photo, I used a lens opening of f13 with an ISO setting of 200. My histogram showed this to be the correct exposure for this scene. I was shooting horizontally so the background water exposure was very close to f13. Therefore, the shutter speed of 1/60th second that the camera chose was all that was required for this photo. In the example on the right, I was shooting towards the surface. The lens opening of f13 was correct for the flash output. The background water color was too bright for the combination of ISO 200, f13 and 1/60th of a second. The camera chose a shutter speed of 1/180th second to provide a better background exposure. I didn't do anything to make the choice. The camera really helped me here.

Digital Rebel & Aperture Priority
When Robin shot her Digital Rebel in Aperture Priority with an underwater flash (Ikelite Substrobe 200), the camera did not limit itself to a range of shutter speeds faster than 1/60th of a second. Instead, it used very slow speeds when the light level was low. This was always true since Robin was using small lens openings (ex: f8, f11, f16 or f22) for greater depth of field. The camera would use shutter speeds much slower than 1/60th of a second. I saw shutter speeds as slow as 1/20th of a second. This is too slow a speed for sharp exposures. The result was blurry images.

Program Mode and Exposure Compensation
In the Aperture Priority mode, Robin would look at her histogram after the shot and use exposure compensation to change her exposure. This is very similar to fooling a Nikonos V camera by bracketing using the film speed dial. What we found was that it was too difficult to change exposure compensation with her camera.  It was a two step process and it took too much time and she had to take her eye away from the viewfinder to make the change. This is okay if you are shooting static subjects but not great when shooting fish and subjects that move.

Solution - Shoot in the Manual Mode
We solved this problem by shooting in the manual mode. Talk about going back to basics. The upside is that with a histogram, it is so much easier than it ever was with film. Robin used an ISO setting of 100, set the shutter speed to 1/125th of a second, and changed lens openings to fine tune her exposures. Of course, she used the histogram after each shot to see what changes needed to be made. On the Ikelite housing for the Digital Rebel, the lever that pushes in the exposure compensation button (required to change lens openings in the manual mode) is spring loaded and Robin just left it in place on the exposure compensation button. Changing lens openings after that was just a matter of turning a dial. She found this setup easy to use and could make exposure changes with a minimum of fuss. If you are new to digital photography, do not let manual exposure make you nervous. First, learn how the histogram works and how to make changes in lens openings to make your exposure better. If you go in the wrong direction, don't worry. Look at your histogram and you will see that you went the wrong way. You can then compensate in the right direction.

The Proof is in the Results
Robin's results were impressive. We both agreed that she had more keeper photos from this one trip than she had in all of her film underwater photo trips combined. With her permission, I have included some of her photos below. Robin shot in the manual mode with macro subjects, fish subjects and with wide angle subjects. The wide angle shooting required an additional step which I will outline on another page.

I shot for most of our week in the manual mode also. I thought that after all these years of shooting, going back to basics was refreshing. In a future page, I will show you results from my Nikon 12-24mm zoom lens when shooting in the manual mode.

Samples - The following are examples of Robin Reed's underwater photos from our trip to the northern Bahamas in May of 2004 on the Nekton Rorqual.

French Angelfish

Scrawled Cowfish

Great Altantic Barracuda

A Word of Caution

Digital photography renewed Robin's interest in underwater photography. It does cause a problem that all aspiring digital underwater photographers should recognize. Robin was using a 512mb compact flash card and shooting jpegs. This gave her the capability of shooting a few hundred images on a dive. It became very easy to lose track of bottom time or the amount of air remaining. Please remember to check your bottom time and remaining air often. It's way too easy to get so caught up in photography that you overstay your bottom time or run out of air. When I turned to digital photography underwater, my wife, Veronica, and my dive buddy, Beth Dalzell, made me learn a new mantra: AIR - BOTTOM TIME - PHOTOS . The list is in order of importance. I recite it often.

Shooting wide angle in the manual mode with the D100 and the Nikon 12-24mm zoom lens.