Telephoto Lens

Photography is a major industry, both in regards to the sale of domestic digital cameras and also in terms of the celebrity photograph market. Quite clearly in order to capture photographs of different qualities and also from different distances, a range of camera lenses are required. One example of this is the telephoto lens. The telephoto lens is a long focal length camera lens; the main point of this type of lens is that the physical length of the lens is shorter than the focal length. The optical centre of this type of lens is located outside of the actual physical construction of the lens. For a lens to be categorised a telephoto lens, the lens must feature a special kind of lens from the telephoto group. Although must be noted that many long focused lens are also described as telephoto lenses despite this being factually incorrect.
The centre of a lens is described as the optical centre of the lens; this is a standard term throughout lenses, not just telephoto lenses. A telephoto lens operates in different ways to traditional long focal lenses, a telephoto one works by having the highest light gathering element of a much shorter focal length than the equivalent long focus lens. A second set of elements is also incorporated close to the film or sometimes close to the sensor plate. Having this second set of elements helps to cont the light so that it appears to have come from a lens which has a much longer focal length.
One of the most popular lens makers within the world is the designer Carl Zeiss, he is extremely well known for producing lenses for the major brand Sony. Zeiss has also produced the heaviest telephoto lens; it has a focal length of 1700mm and produces an entrance pupil of 425mm. The lens was produced for use with a medium format Hasselbad camera, which weighs an incredible 256kg.
The purpose of the telephoto lens and also other long focal lenses is to make distant objects appear close, or magnified. Quite clearly the effect is similar to moving close to the object although it provides a completely different perspective. The telephoto lens will compress the distance between any objects within a photograph, this due the photograph being taken from a distant location. The long lens provides the photographer with much more choice and diversity in regards to how they take their photographs. They provide the photographer an alternative from the perspective distortion which is provided from traditional short focal length lenses, which often lead to objects in photographs being disproportionate.
These kinds of lenses also enable the background of photographs to be blurred with ease, this is a very popular with photographers photographing celebrities. A blurred background means only the central object is focused on by the person viewing the photograph, and also means that only the main point of a photograph is viewed.