Collins Complete Photography Manual. Collins Dictionaries

body and the lens and magnify the image by a fixed amount, such as 1.4x, 2x or 3x. They are a much cheaper alternative to long-range telephoto lenses, but they do have drawbacks. The most serious is that they reduce the maximum aperture of the lens. A 1.4x converter will reduce the aperture by 1 stop, a 2x converter by 2 stops and a 3x converter by 3 stops. This reduction in the size of aperture increases the risk of camera-shake or subject movement in low light levels.

      Specialist Lenses