T Telephoto Lens 244 A type of long-focus lens with an optical design that means it is physically shorter than its optical focal length. The terms long focus and telephoto are used interchangeably nowadays but there is this technical difference. Telephoto lenses have narrow angles of view and long focal lengths. For 35mm and full-frame digital cameras, a 135mm lens is considered a short telephoto. True telephoto lenses start at a focal length of 180­200mm. Many telephoto lenses are now designed as zooms, bar the extreme focal length lenses between 800 and 1200mm, which are sometimes folded mirror (reflex) designs for compactness. The classic background blur and pronounced depth-of-field changes can be seen here. This image was taken at the 300mm end of a 70­300mm f/4-5.6D AF ED Zoom-Nikkor, fitted to a digital camera body with a crop factor of 1.5, making this act like a 450mm telephoto. see Angle of View 26