<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2010) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2010) (Learn how and when to remove this template message) </Td> </Tr> <P> The Canon EF - S lens mount is a derivative of the EF lens mount created for a subset of Canon digital single - lens reflex cameras with APS - C sized image sensors . It was released in 2003 . Cameras with the EF - S mount are backward compatible with the EF lenses and, as such, have a flange focal distance of 44.0 mm . Such cameras, however, have more clearance, allowing lens elements to be closer to the sensor than in the EF mount . Only Canon cameras released after 2003 with APS - C sized sensors support the EF - S mount . </P> <P> The "S" in EF - S has variously been described by Canon as coming from either "Small image circle" (the lens projects a smaller image circle than normal EF lenses to match the sensor), or "Short back focus" (the smaller mirror used in APS - C cameras also allows optical elements to protrude further into the camera body, reducing the minimum distance between the sensor and the back element of the lens). The combination of a smaller sensor and shorter back - focus distance enhances the possibilities for wide angle and very wide angle lenses, and enables all lenses designed for the EF - S mount to be made smaller, lighter (containing less glass), faster (larger aperture) and less expensive . </P>

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