Telephoto Lens in Digital Photography are mainly intended for DSLR and with respect to a standard lens, has long focal length and a smaller angle of view. From technical or optical aspect, telephoto lens is kind of lens which extends the light path to optically emulate a typical long-focus lens with a much small overall design.
Optical Properties of Telephoto Lens
A typical Telephoto lens is usually designed to be mounted on a DSLR Camera. Telephoto lens are not to be confused with zoom lenses that allow for adjustment of the focal length, but do not necessarily achieve the optical character of a telephoto lens. In the area of macro photography, telephoto lenses allow a greater working distance between the lens and the photographic subject than the standard lenses or wide angle lenses , for example, making the lighting options can be simplified.
Variants of Telephoto Lens
Telephoto lens can be divided into different classes depending on the focal length and primary application.
Telephoto Lens intended to be used as Portrait Lens
Portrait lenses with focal lengths between about 80 mm and 105 mm, sometimes up to 135 mm due to the decreased depth of field and receives the perceived distortion as a pleasant, like for portrait photography and are used to extract the person from the background. Objective of this focal length works in low light conditions can usually still be safely used without a tripod. Angle can be from 24° to 28°30′.
Standard Telephoto Lens
Than standard lenses are telephoto lenses with a focal length of between about 135 and 200 mm. With the lenses of this focal length range, using a tripod and fine tuning ISO prevents shake induced blurring.
Super Telephoto Lens
Telephoto lenses with focal lengths of 300 mm, are based on the small format are known as super-telephoto lenses. Especially in the animal photography and sports photography these are helpful.
Telephoto lenses with about 200 mm focal length can deliver very good image quality, relatively they are compact and inexpensive. Lens aberrations become more apparent after a focal length, so that a considerable engineering effort is used. Those telephoto lenses require special optical glass and aspherical lens.
Manufacturers can use confusing terminologies but these are the correct descriptions and can be taken as the standard.
- R. E. Jacobson, The manual of photography: photographic and digital imaging
- Edward John Wall and Thomas Bolas; The Dictionary of Photography for the Amateur and Professional Photographer