Express Action Sports

A telesphoto lens tends to be of a fixed focal length and magnification. Zoom lens are similar to the lens you have, giving you adaptability. For example, A 200mm telephoto lens is just that, a fixed 200mm lens where as say a 200-500mm zoom lens give you 200mm through 500mm to play with.
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A telephoto lens is fixed focus. 150mm or 200mm or whatever. A zoom lens can move between a certain range…in your case 18mm and 55mm. You should be able to find a zoom lens that has greater magnification than the one you’re using now. Like a 28-200mm.
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http://photonotes.org/articles/beginner-faq/lenses.html

Your 18-55mm lens is a zoom lens, all it means is that the lens has a variable focal length between X and Y.

A telephoto lens is one that is greater focal length than the "normal" lens for a particular type of camera. On a 35mm, that is anything more than 50mm. On a 645 or 6X6, that is anything greater than an 80mm.

On your Digital Rebel with the 1.6x crop factor, it is anything greater than about 35mm. Your 18-55 is actually a short telephoto, with an equivalent field of view of approximately 29-88mm as compared to a 35mm camera.

What you can get to fulfill your need varies mostly with your budget. The Canon 75-300 III is the least expensive method to get a lot more reach, but is also the worst option. Better, yet still fairly low cost, is the Sigma 70-300 APO. Make sure it is the APO version, there are several.

Upping the budget a little, there is the Canon 55-250 IS, supposed to be a pretty good lens.

For another step up in price, there is the Canon 70-300 IS, which is an image stabilized version of the lens, but is a much better lens to begin with. For only a little more, you can get the Canon 70-200 f/4 L, a constant aperture zoom. Anything with an L in the name is a good lens. Even the 28-300 IS, even though it costs $2,300.
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A telephoto lens is a lens that makes the subject appear nearer than normal, telescope effect. With most crop-size sensors, normal is around 33mm so anything above that is telephoto. On an 18-55mm zoom lens, 55mm is telephoto.

To achieve more magnification, you get a lens with a longer focal length or more mm. You can get a 200mm, 300mm, 500mm or 1000mm, whatever you can afford.

You will notice that my suggestions above only have one number each. These are prime lenses, those that do not zoom. They are generally more expensive than zoom lenses. Zoom lenses are lenses that can vary focal length like your 18-55mm zoom lens. This means that you can shoot wide at 18mm but if you want to go closer, zoom to 55mm.

A zoom lens may have telephoto capabilities so it is possible to have zoom and telephoto at the same time within the same lens. The 18-55mm lens is an all-purpose lens that goes from wide to telephoto. A 75-200mm lens is a telephoto zoom lens that goes from tele to super telephoto.

In the unlikely event that you find Canon lenses too prohibitive to acquire, rather than get a poor alternative, you can always use the original zoom method invented years before the first zoom lens was made. It’s called walking. Simply approach your subject until you get the effect you want to achieve.
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Never mind the difference, for action and sport, you are going to need at least the
100-400mm L IS. Anything less than 100mm is going to be too short, and more
than 400mm is almost impossible to hold. That is why the 100-400mm is so nice,
it covers most of the range usually found in sport.
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