Canon® EOS Digital Photography Photo Workshop

4.4. FOCAL LENGTH AND APERTURE EFFECTS

While some photography technologies relate only to your camera's internal operation, and knowing them won't necessarily make you a better photographer, understanding some others can have a direct impact on your compositional skills and your ability to control your camera more completely.

4.4.1. FOCAL LENGTH AND IMAGES

Knowing the relative behavior of lenses, how focal length works with them, and how they will work with and be effectively applied to various subjects is essential to producing good photography. The relative sizes and perceived distance between objects change as focal lengths change, whether in a zoom lens or by using different lenses. Of course, to achieve a similar photo with a wide-angle versus a telephoto lens — say, for example, an image of a house that shows the entire building — you need to physically change your position to get closer or farther depending on your lens's focal length. A telephoto lens will make a row of racing cars, viewed head-on, look far closer to one another than they really are, while with a slightly wide-angle lens you might need to have a family pose closer together than might seem natural because the lens will spread them apart somewhat.

Other factors are affected by focal length, as well; telephoto lenses, for example, are susceptible to camera shake and can produce blurry images with minimal movement because their focal length is so long (which, once again, is why image stabilization is helpful). ...