The Canon EF 25mm Extension Tube II is used to allow a lens to focus closer than it dwould normally. This is accomplished by moving the lens 25mm farther away from the camera body's film plane or digital sensor by fitting between the camera body and the lens. Extension tubes are thus commonly used for macro photography and sometimes for closeup portraits and when using the camera's TTL metering system, no exposure compensation will be required. This updated version II is now also fully compatible with Canon Digital EF-S mount, as well as standard photo EF and TS-E fittings. Extension Tube EF 25 II is recommended for focal lengths of 50mm and up (EF-S 18-55mm can be used at middle and tele zoom settings).