Canon Inc. has produced seven different 24mm lenses for its Canon EF and EF-S lens mounts. Three have been discontinued after updated replacements were announced.
EF 24mm f/1.4L USM, introduced December 1997. (discontinued in 2008, replaced by EF 24mm f/1.4L II USM)
EF 24mm f/1.4L II USM, introduced December 2008.
EF 24mm f/2.8, introduced November 1988. (discontinued in 2012, replaced by EF 24 f/2.8 IS USM)
EF 24mm f/2.8 IS USM, announced February 2012, available since June 2012.
EF-S 24mm f/2.8 STM, announced September 2014. Unlike the other 24mm lenses, it will mount only on bodies that support the EF-S mount. It will mount on all current Canon DSLR bodies with APS-C sensors, as well as older APS-C bodies dating to the 2003 introduction of the EF-S mount (in other words, the EOS 10D and older bodies are not compatible). It will not mount on any DSLR body with a full-frame or APS-H sensor. It also cannot directly mount on Canon's mirrorless bodies (either the APS-C EF-M mount or the full-frame RF mount), but the company sells adapters that allow EF-S lenses to be used on either mirrorless mount. As it is designed for Canon APS-C bodies, its field of view is equivalent to a 38mm lens on a full-frame sensor, and operates similar to the Canon EF 40mm f/2.8 STM pancake lens. Compared to the EF 24 f/2.8 IS USM, the EF-S lens loses IS, but lists for about a fourth of the price. The STM offers advantages for video shooting over USM, specifically quieter autofocus.
TS-E 24mm f/3.5L, introduced April 1991. (discontinued, replaced by TS-E 24mm f/3.5L II)
TS-E 24mm f/3.5L II, introduced June 2009.
View More On Wikipedia.org