Article ID : 00007752 / Last Modified : 10/31/2013

What do the numbers and letters mean on interchangeable lenses?

Applicable Products and Categories of This Article

Basic lens specifications are inscribed on interchangeable lenses. The numbers and letters provide the focal length, maximum aperture (f-stop setting), filter size, and other information related to the lens.

For example, on the front of the SAL1870 lens the inscription reads: DT3.5-5.6/18-70 and 0.38m/1.3ft MACRO and Ø55. The DT prefix indicates that the lens is specifically designed for use with APS-C format digital SLR cameras. The 3.5-5.6 numbers indicate the maximum aperture (f-stop setting) possible at the shortest and longest focal lengths. The 18-70 indicates 18mm is the shortest focal length and 70mm is the longest focal length. The 0.38m/1.3ft designation indicates the minimum focusing distance of the lens in meters and feet. The Ø55 indicates the size (in millimeters) of filter you can attach to the lens.