Digital Photography Technology

A telephoto lens. or long focus lens as they are sometimes called, is a lens most photographers would like to have in their camera carrying case. A telephoto lens is not used all the times but there are times when it is needed to get the picture.

Depending on the photographer will determine what their lens requirements are. If you are a sports photographer, telephoto is a must have. For a nature photographer, especially for birds and wild animals, to get the picture, a telephoto lens is needed.

Everyone else can still use a long lens. When taking a picture of a group, a telephoto can be used to single out a particular person. The same when taking pictures of some flowers, but you can not get close enough, the telephoto will do the job.

There are no end of possibilities for a telephoto, but like anything else, there are some down sides.< p> First of all, to design a telephoto, more glass is needed, weight come with more glass, and also price. The lens will weigh more than the camera and cost more, depending on the focal length of the lens.

The focal length of a standard lens is 50mm and as soon as you go any appreciable length over that, it becomes a telephoto. As in any other camera lens, they come in prime or variable focal lengths. p>What we will discuss here will be prime lenses. There are numerous trade offs when purchasing a lens, especially a telephoto. Cost goes up dramatically with speed and focal length. The average amateur photographer can probably afford a 300mm lens at f4. As soon as you go over those figures, you can figure to spend well into the thousands.

Some manufactures attempt to keep the price down, but the speed of the lens will suffer and will be about an f6.3, which is getting slow. Sometimes you can find a good used, manual focus, fixed focal length lens for a reasonable price.

The possibility for increasing focal length is to acquire a teleconverter. This is a secondary lens that fits between the camera and the lens. It comes with multiplying factors and 1.4x, 2.0x, and 3x. A 300mm lens and a 1.4x converter would now be 420mm and a 2.0x converter would be 600mm. This all sounds great, as the converter can be used with any lens, although it is best to be from the same manufacturer of the lens.

The disadvantage of this combination is that light is lost. If a 2x is used, twice the light with be lost. Gain something, lose something. There is also more possibility of distortion and amplifying any imperfections that might be in the lens.

The last of the problem are the weight and bulk of a large lens. Depending on the lens, they can weigh one or two pounds and up to10 pounds for a 300mm at f2.8. With weight comes the problem of stability. These large lenses can not be hand held. Movement is critical and a good tripod is a must. Shutter speed has to be increased, which mean more light is required. Due to the large size of the lens front element, any filters that are used will very large and expensive.

Zoom telephotos are available, but to keep the same focal length size as the same prime, they will be larger yet. To keep weight and size down, plus cost, the lens speed will have to be sacrificed.

The last possibility is a mirror lens. They normally come in 500mm/f8 and 1000mm/f11. There is no aperture adjustment and the depth of field is very narrow. They are also relatively large, and require a tripod.

This hopefully will help you decide on the purchase of a telephoto lens. They are great to have when the need requires one.