Telephoto lenses are useful in a variety of different situations, and aren't strictly for wildlife. They are a great tool for any photographer and a must have in your camera bag because of the different situations you can use them in. However, because of their extreme sensitivity to camera motion you must be careful to hold your camera steady and your sharp pictures will thank you.
Definition
Telephoto lenses have a large focal length, ranging usually between 135mm and 300mm, although there are super telephoto lenses which go up to 800mm. The larger the focal length number the closer you can visually get to your subject, especially if it is at a far-off distance. "A longer focal length effectively compresses the distance between the subject and camera," according to Canon. Telephoto lenses are generally a set focal length, whereas telephoto zoom lenses can actually zoom between different lengths, for example a 70mm-200mm lens which can cover anything in between those lengths.
Uses
Telephoto lenses have a wide range of uses from sports, to wildlife, to portraiture. These lenses are especially useful for subjects that you cannot physically get close to, such as a bird that would be frightened away by your presence.
Because telephoto lenses are great for shooting at a distance, they can be beneficial for portraiture, especially when photographing children. Young kids can be shy when having their picture taken, so it's to your advantage to shoot from a distance so you don't disturb their normal behavior and can capture memorable moments. Tele lenses also crop out surrounding distractions and provide a favorable background blur so that they don't detract from the subject
Sharp Pictures
It's important to note that your shutter speed will play a large roll into how sharp your final image is captured, especially if you're trying to hand hold the camera. A good tip is to brace yourself against a tree or wall.
Telephoto lenses are extremely power magnifiers and because of this they are sensitive to camera shake. A good rule of thumb is to use a shutter speed no smaller than the reciprocal of the focal length of the lens. For example, if you're telephoto lens is a 200mm, then your shutter speed should be no slower than 1/200 of a second.
Use a tripod whenever possible to ensure that your pictures come out sharp.This will minimize virtually all camera shake and provide a sturdy base for your camera.
Tags: focal length, Telephoto lenses, shutter speed, your camera, camera shake, different situations, lenses have