ABSTRACT
The majority of cameras are purchased with a lens of ‘standard’ focal length for the film format. If the lens is not interchangeable, then it is almost certain either to be standard or slightly wide-angle for the format, or to have a short-range zoom lens including the standard value. The concept of a standard lens also provides a convenient index for classification of lenses by relating their diagonal field angle of view for a format rather than by focal length. Improving the performance of standard lenses was once the mainstream of lens design efforts, and almost all configurations have been used. The standard lens generally represents excellent value and is highly corrected and representative of the state of the art in optical design. The standard lens is usually considered to be a general-purpose lens, and is extensively used on medium- and large-format cameras where the larger image and subsequent enlargement can substitute for lack of a long focus lens.
