An extension tube is a non-optical device which increases the distance between the lens and the film or sensor. This allows the lens to focus much closer than normal, giving increased magnifications. Suitable for macro work with Canon digital SLRs.
The Extension Tube EF25 adds just over 25mm of extension. It is provided with a full set of EF lens contacts, which allow shooting data to pass between the lens and camera. All camera exposure modes can be used, but spot metering is not possible. A few wide angle EF lenses cannot be used for practical reasons.