I recently went whale watching off the coast of Gloucester, and it was an absolute thrill. Mother and calf humpback; breaches; tail flaps; fins splashing in all directions. So it was with considerable anticipation that I downloaded the photos into Aperture and then… utter disappointment.
But before I dissect what went wrong, check out the gallery at the end of this post.
There were 2 obvious issues. First were the blurry photos caused by camera shake. Most of these were my quickly panning to catch a shot, so I wasn’t too annoyed with these. However, I do need to pay more attention to the 1/focal length rule – Set your shutter speed to 1/L and you should be in good shape. For these shots, that would have been 1/300 s, whereas I was often shooting at slower speeds. Ideally, I’d shoot in auto ISO mode (I love my D200), and set the minimum shutter speed to 1/300 s. Problem 1 solved.
The second problem was more disheartening. Many of my photos, while clearly in focus, were blurry. And I quickly realized that my depth of field covered only the front part of the whale. The photo at left shows this quite clearly. Note the leading edge of the focal plane is near the front edge of the whale (look especially at the water, along a line about 1/3 in from the left). But the back edge of the whale is already out of focus. My DoF was far too shallow.
Back home, I did the calculation. At 70 feet (the whale may have been even closer), 200mm lens DX format, f/5.6, my total DoF was 8.4 ft – and only 4.45 feet of that is behind my focus point. Obviously, that is not nearly enough depth of field for a humpback whale!
I have now done what every current photographer has done: picked up a DoF calculator for my ipod touch. Now, when I’m on the boat, I’ll know that for a whale 70 feet away I should set my aperture in the neighborhood of f/16 (24.37 feet total DoF, 14.24 feet behind) for the whales to be safely ensconced in my depth of field.
An important lesson for me to learn. From now on, I will pay much more attention to DoF.
