It can be difficult to make a good photograph of a bird. There are practical and technical reasons for that. Birds are small, fast, and shy so it is hard to get close enough to a wild bird to take the picture. Most photographs of birds are taken with telephoto lenses, lenses which magnify objects, making them appear closer and larger than they are. The technical reasons are the laws of physics. Light entering a camera lens, like light entering our eyes, behaves according to those laws. For bird photography, that light usually enters a telephoto lens. Because of how such lens must be built, the background of the photo is thrown out of focus. Photographers refer to this as a “shallow depth of field.”
Let’s compare a couple of photos. (You can double click on either to see an enlarged version.) The first is an Ansel Adams photograph of birds on a beach. Notice that everything you see in the photo, from the beach in the foreground all the way to the sun in the background, is in sharp focus. That is because Mr. Adams used a very small aperture (hole)to take the photo which resulted in a large depth-of-field. (Everything in focus) Notice how small the birds are. If Adams had wanted to make the birds the center of attention in the photograph he would have had only two choices; get closer or use a telephoto lens which would have made almost everything else in the photograph unfocused.
Now look at this photo of a male Bobolink. If the photographer had used a small aperture like Adams did everything in the photo would be in focus but the Bobolink would have been tiny. But had the photographer tried to get close, the bird would have spooked and flown away. Because the bird was the subject of the photograph, the photographer had to use a telephoto lens to magnify the bird in the resulting print. That lens, because of those laws of physics, had to have a large aperture which resulted in the unfocused background. If you look at the bottom of the photograph, you’ll notice some out-of-focus flowers in the foreground as well. That was not the photographer’s fault. His lens could only focus in a small range of distance from the lens because it has a very small depth-of-field. (The bird and the plant he is perched on are in the same “plane,” hence focused. The photographer could have cropped the out-of-focus foreground out of the picture, but there was nothing to do about the background.)
There is nothing wrong with this kind of documentary telephoto photography and we have many thousands of wonderful close-up images of birds as a result. But, when you’ve seen many thousand such images, you begin to yearn for something different. We’ll talk about that in the next post in this series. We’ll move from visually recording birds to artistic explorations of them.