sailorsmom Loc: Souderton, PA

What is the difference between a zoom lens and a telephoto lens?

RocketScientist Loc: Littleton, Colorado

At the Canon camera museum http://www.canon.com/camera-museum/camera/lens/ef/standard_zoom.html

They seem to differentiate between the two as zoom is adjustable focal length while telephoto are prime lenses

egnblack Loc: San Jose, Ca.

Exactly correct. A zoom lens changes its' focal length, while a telephoto is a fixed length long lens. You can also have a zoom telephoto lens.

PhotoMan1929 Loc: Virginia, USA

As others have noted, a "zoom" lens has a range of focal lengths, whereas a "telephoto" lens, strictly speaking, is a lens with a long focal length and a relatively short physical length. Unfortunately, many people refer to any long focal length as a "telephoto."

The telephoto designs came into use in the early 20th century, in the days when view cameras were widely used by pro photographers. The telephoto design could get a long focal length without a long bellows extension which would have made the camera more susceptible to vibration from wind, etc.

Ottsy Loc: Elkridge, Md.

Zoom lenses have variable focal lengths as opposed to a prime lens which only has one. Naturally zoom lenses are more versatile, but a good prime lens is usually faster (more sensitive to light) and usually of better quality.