There are two primary elements of choosing and using a lens: what focal length to use and where to focus/what aperture to use. Let’s take a look at how these elements affect an image.
How Does Focal Length Affect Your Image?
The only thing that changes when you use a different focal length lens is the cropping of your image!
Optical aberrations aside, short focal length or wide angle lenses do not distort close subjects, and long focal length or telephoto lenses do not compress subject features. What really causes these familiar effects discussed so often in popular texts is a change of perspective: a change in the camera’s physical position relative to your subject. (Figure 2).
When you move in close to a subject, it becomes very large in relation to its background. That over- large nose you get with a wide angle lens portrait is because you’ve probably moved in very close to the subject in order to fill the frame, and the nose, being closest to the lens, is now very large in relation to the ears. This is a matter of your proximity to the subject and has nothing to do with the lens itself. (Figure 1).
When you look at a distant scene through a long focal length or telephoto lens, elements in the scene may appear compressed, almost right on top of each other. Once again, this has nothing to do with the lens, but is simply a matter of the tight framing on the subject. If you put the camera down and frame the scene just as tightly with your hands, the elements of the scene will appear as “compressed” as they did through the lens.