I was wondering how can you tell if a lens is telephoto?

Question

I ordered a camera for my sister and she wanted to a telephoto lens...It came with 2, and I was going to order another one but I want to make sure that I don't already have a telephoto lens.. How do you tell?

Answer 1

You can tell by its focal length. Many photographers usually call "telephoto" any long lens, even though a real telephoto is a specially built lens, so that the actual length of the lens is shorter than its focal length. A normal or standard focal length for a 35mm film camera is 50mm. For a digital camera it can be shorter. So, a 70mm or an 85mm lens can already be considered a telephoto. A common telephoto for a 35mm camera is 105mm, but there's also much more poweful ones (200mm, 300mm, 400mm, 500mm, etc... and even 1000mm and up).
Many cameras, however, come with zoom lenses that combine a range of focal lengths into one lens, from wide angle to telephoto, but this range isn't usually very broad, like 28mm to 90mm or something slightly below/above that range.
So, just check what the length of your lenses is. You may already have a telephoto lens. But you may also want to buy a longer one if you need to take pictures of very distant objects you can't get close to (ex. wild animals, birds, the moon). Keep in mind however, that a very long lens is usually very expensive and the longer the lens, the more difficult it is to focus -- it magnifies the slightest camera movement so your pictures can come out blurry if you don't use a tripod.

Answer 2

For 35mm film cameras, telephoto would mean lenses with focal lengths longer than normal (50mm). But on some digital SLR cameras this has changed because the lens elements are relating to digital light receiver that is smaller than a 35mm negative.
For instance, on my Canon Digital Rebel, my 50mm film lens is actually closer to 80mm (a telephoto lens). My digital zoom lens of 18-55mm is similar to a 28-90mm film lens (which is actually a wide-angle, normal and short telephoto lens all in one). There's a fairly big selection of wide-angle to telephoto zooms available.

So for some digital lenses and cameras, normal would be around 30mm or so and telephoto would be over that. Some camera brands also sell devices called telextenders that will lengthen the reach of your lens (although you will lose a few stops of light in aperture in the process).

It's also important to remember that telephoto is the opposite of wide-angle. Where a wide-angle lens pushes away from the subject, the telephoto grabs it and pulls it closer. Both will distort the true image in a way. While the wide-angle lens reveals a wide field of view, the telephoto's field of view is very narrow.

Depth of field (the amount of sharpness in the area in front of and behind the focal point) also decreases with telephoto lenses and increases with wide-angle. This is another reason why telephoto lenses are better traditional portrait lenses.

Answer 3

The name telephoto goes in direct relation to the diagonal of the negative; the 35mm cameras produce a negative of about 50mm diagonal, so, any focal length bigger than that is consider telephoto, and any shorter will be called wide angle.
There will be 'extreme telephoto' like 1000mm focal length.
The most common TPlens ranges from 70mm to 300mm with several in between.
The WA lenses are below 40mm focal length, going to the extrem ones called 'Fish eye'