Canon Extension Tube Ef 25 Ii These close-up accessories are placed between the camera body and lens to enable high-magnification photography. Eight electronic contact points allow communication between the camera and lens to continue as usual. The magnification differs according to the lens, but for standard zoom lenses it is about 0.3x to 0.5x for the EF 12 and 0.7x or more for the EF 25. By using both tubes effectively, the choice of magnifications can be greatly extended. However, for best results, manual focusing is recommended.