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 magnification. Suitable for Macro work with Canon Digital SLRs.
Like the EF25, the Extension Tube EF12 is a non-optical accessory. It is about half the length, extending the distance between the lens and the film by just over 12mm. This gives less magnification than the EF25 tube. With both Extension Tubes, autofocusing may operate in some conditions, but will not always be available. Manual focusing is recommended, since a slight change in focus at close distance can have a major effect on the image. The EOS autofocus system can be used for focus confirmation.