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Tuesday, December 1, 2009

Choose Your Perfect Zoom

The modern zoom lens is a marvel of technology, and it’s the nature photographer’s best friend

This Article Features Photo Zoom

Zuiko Digital
ƒ/2.8 SWD
You can change a composition (framing) and the subject size by changing focal length or by changing camera distance. Each method produces a different effect.

When you simply change focal length, whether by zooming or by changing from a prime lens of one focal length to a prime of another focal length, the perspective doesn’t change. You’re just changing the framing. A longer focal length shows less of the scene and makes the subject (and everything else in the frame proportionately) larger; a shorter focal length shows more of the scene and makes the subject (and everything else in the frame proportionately) smaller.


When you actually move the camera closer to or farther away from the subject, you change the perspective as well as the framing: When you move closer, the subject grows larger not only in the frame, but also relative to its surroundings. When you move farther away, the subject not only becomes smaller in the frame, but it becomes smaller relative to its surroundings. That’s a change in perspective, and it happens because you changed the camera-to-subject distance. Merely changing the focal length does not change perspective; you have to change the camera-to-subject distance to do that.

Pentax DA
We think of wide-angle lenses as expanding perspective because we generally move closer to our subjects when using a wide-angle lens. And we think of telephoto lenses as compressing perspective because we generally use telephotos to photograph distant subjects. But it’s the camera-to-subject distance, not the focal length, that changes the perspective.

You can demonstrate this for yourself. Put your camera on a tripod, attach a telephoto lens, and take a photo. Remove the telephoto lens, attach a wide-angle lens, and take another photo. At your computer, blow up the wide-angle shot so it covers the same area as the telephoto shot, and examine both images. You’ll see that the perspective is identical: The subject’s size relative to its surroundings is the same (of course, the wide-angle image will be much “grainier” due to the degree of enlargement).


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