Editing 135 film (section)

== Lenses ==

A true [[normal lens]] for 35&nbsp;mm format would have a [[focal length]] of 43&nbsp;mm, the diagonal measurement of the format. However, lenses of 43&nbsp;mm to 60&nbsp;mm are commonly considered ''normal'' lenses for the format, in mass production and popular use. Common focal lengths of lenses made for the format include 24, 28, 35, 50, 85, 105, and 135&nbsp;mm. Most commonly, a 50&nbsp;mm lens is the one considered ''normal''; any lens shorter than this is considered a ''wide angle'' lens and anything above is considered a ''telephoto'' lens.  Even then, wide angles shorter than 24&nbsp;mm is called an ''extreme wide angle''. Lenses above 50&nbsp;mm but up to about 100&nbsp;mm are called short telephoto or sometimes, as ''portrait telephotos'', from 100&nbsp;mm to about 200&nbsp;mm are called ''medium'' telephotos, and above 300&nbsp;mm are called ''long'' telephotos.

With many smaller formats now common (such as [[APS-C]]), lenses are often advertised or marked with their "35&nbsp;mm equivalent" or "full-frame equivalent" focal length as a mnemonic, due to the historic prevalence of the 35&nbsp;mm format. This 'equivalent' is computed by multiplying (a) the true focal length of the lens by (b) the ratio of the diagonal measurement of the native format to that of the 35&nbsp;mm format.

As a result, a lens for an APS-C (18×24&nbsp;mm) format camera body  with a focal length of 40&nbsp;mm, might be described as "60&nbsp;mm (35&nbsp;mm equivalent)". Although its true focal length remains 40&nbsp;mm, its angle of view is equivalent to that of a 60&nbsp;mm lens on a 35&nbsp;mm format (24×36&nbsp;mm) camera. Another example is the lens of the 2/3&nbsp;inch format Fujifilm X10, which is marked with its true zoom range "7.1–28.4&nbsp;mm" but has a 35&nbsp;mm-equivalent zoom range of "28–112&nbsp;mm".