Zoom and Telephoto

[pmillage]

Good Day;
Can someone tell me the main difference between zoom and telephoto? I know zoom changes the range between wide angle and close up but doesn't telephoto as well?...cheers everyone

[Chip]

Here's my understanding:

A zoom is a lens that can change focal lengths. Zooms can be wide angle, such as 11-16 mm, or longer, such as 70-300mm.

A telephoto lens just means one that has longer reach. So, an 80-400mm zoom would be telephoto at the longer end. And a 400mm prime would also be a telephoto - but, since it's a prime, by definition, it's not a zoom.

So, to sum up, a zoom may or may not be a telephoto. If depend on the focal length at the long/longer end.

If I'm off or incomplete, I'm sure one of the more knowledgeable folks here will chime in.

[jamesev]

Difference Between Zoom and Telephoto | Difference Between | Zoom vs Telephoto

[Doug Pardee]

Originally Posted by pmillage

Can someone tell me the main difference between zoom and telephoto?

There are two answers to that, because common usage no longer agrees with the formal definitions.

Common usage:
A telephoto lens is one that gives a more magnified image that a normal lens. There is no official standard for a normal lens, but most folks are willing to accept a number of somewhere around 45-50mm for 35mm film.

A zoom lens is one that gives a continuous range of focal lengths to choose from. There are wide-angle zooms, telephoto zooms, and wide-to-telephoto zooms. Most kit lenses are in the "wide-to-telephoto zoom" category.

Formal definitions:
A telephoto lens is one in which the physical length of the lens is shorter than the focal length (a bit of handwaving in there). This is accomplished by adding a lens group called a telephoto group to the lens design.

A zoom lens is one which provides a continuous range of focal lengths, and where changing the focal length does not adjust the focus distance. This is very important in movie and video photography, where the zooming often occurs while recording and you don't want the focus to wander. (This characteristic is called being parfocal.) Almost all lenses for still photography are varifocal lenses, which means that they provide a continuous range of focal lengths but the focus distance might vary during focal length adjustment.

Examples:
An 85mm lens is often considered to be telephoto even though it probably does not in fact have any telephoto lens group.

An 85mm lens is not a zoom lens. A 17-85mm lens is often considered a zoom lens, because it can be set to any focal length between 17 and 85mm.

A 12-20mm lens is generally considered to be a zoom lens, but it's not telephoto because even 20mm is wide-angle on all current DSLRs.

The kit lenses that come with most DSLRs are considered to be zoom lenses even though the focus distance almost certainly changes as you adjust the focal length. Technically, they're varifocal lenses.