Telephoto Lens

A telephoto lens (or a zoom lens operating at maximum focal length) has a narrow angle of view and makes subjects appear closer to the camera than would be the case with a normal lens. In other words, distant objects in front of the camera are magnified. Although there is no exact definition for the designation “telephoto”, a focal length higher than 60 mm is generally considered a telephoto lens (for cameras that use 35 mm film or an equivalent digital sensor). The upper limit is about 1200 mm. Because of their long focal length, telephoto lenses are sometimes called “long lenses”. Not surprisingly, long lenses have attributes opposite to those of the short lenses ( = wide-angle lenses). The effect of using a long lens is to compress the apparent depth of an image, so that elements that are relatively close or far away from the camera seem to lie at approximately the same distance. This perspective-flattening effect is sometimes called “telephoto distortion”. Telephoto lenses have a small depth of field, which makes them suitable for selective blurring of planes (see selective or shallow focus). Movement towards and away from the camera appears slowed down and de-emphasized.