What does focal length mean on an DSLR camera?
http://www.photoxels.com/tutorial_focal_length.html This one will make far more sense with the photos, which I can’t paste in via NowNow, alas. http://www.hash.com/users/jsherwood/tutes/focal/focal.html Somewhat techie, but shows good illustrations of what different focal lengths can do for or to an image. Why measure Focal Length? Unless you’re testing and calibrating lenses, I’m not sure why you’d want to know the exact focal length of a lens other than simply to satisfy your curiosity. It’s just something that some people want to know. If you pay for a 400mm lens, it’s nice to know you have a 400mm lens, not a 370mm lens I guess. In fact most lens makers will tell you that the focal length marked on a lens is +/- 5%. That means your 400mm could be as short as 380mm and still be “within spec”. Normally telephoto lense
