Primes and zooms

Lenses come in two flavors: prime lenses, which have a single fixed focal…length, that means they have one field of view, and zoom lenses which have a…variable focal length.…So they have a field of view that can go from wide to more narrow.…For the most part a lens with a longer focal length will be physically longer. For example,…I've got this 400mm lens, which is as you would expect much longer than this 50mm lens.…Now I say for the most part, because zoom lenses can complicate things.…For example, I've got this 50mm lens here and then I've got this is a 16 to…35 millimeter zoom.…

It's much longer than the 50. That's because zoom lenses have complex mechanics…and sometimes require extra glass.…So even though this is ultimately a shorter focal length, it's a…physically longer lens.…With primes you'll sometimes find a kind of odd size variation.…For example, here is a 28mm lens and here is a different 50mm lens. The 28mm is…a shorter focal length, but in this case it's a physically larger lens.…