Canon Extension Tube EF 25. In this second issue of Films and Accessories, the focus is on the Canon Extension Tube EF 25, an affordable accessory for those Canon EOS camera owners keen on shooting close-up pictures even if they don't have a bellows unit or any of the three Canon EF Macro lenses. But first of all, what exactly is an extension tube? Anyone familiar with shooting close-up pictures will know what an extension tube is but for those who are new to photography, a bit of information about the tube is required. An extension tube is a non-optical device that increases the distance between the lens and the film. This allows the distance between the lens to focus much closer than normally possible and thus, gave the increased magnifications. Canon has two extension tubes made especially for use with its EOS cameras. The two tubes are the Extension Tube EF 12 and EF 25. The designations of the two tubes refer to the overall length of extensions between the lens and camera body when either tube is used. The EF 12 tube provided a 12mm extension while the EF 25 version adds just over 25mm of extension. Extension tubes fit between the lens and the camera body. The increase in the distance between the lens and the film reduces the amount of light reaching the film but the exposure compensation is provided automatically by the EOS system. For this issue, the focus is only on the Extension Tube EF 25. As mentioned earlier, an extension tube is a non-optical device which is hollow without any lens element in it as can be seen in the above photo of the EF 25 tube alongside the Canon EF 50mm f/1.4 USM standard lens. The EF 25 tube is provided with a set of EF lens contacts that allow shooting data to pass between the lens and any EOS camera body. All camera exposure modes can be used but spot metering is not possible. Canon, however, does not recommend the EF 25 Extension tube to be used with certain wide-angle lenses like the EF 14mm f/2.8L USM, Fisheye-Lens EF 15mm f/2.8, EF 20mm f/2.8 USM, EF 24mm f/2.8, TS-E 24mm f/3.5L, EF 28mm f/2.8, TS-E 45mm f/2.8 and the standard EF 50mm f/1.0L USM lens for practical reasons. The wide end of zoom lenses like the EF 17-35mm f/2.8L USM, EF 20-35mm f/2.8L and the EF 28-80mm f/2.8-4.0L USM are also not recommended to be used with the EF 25 tube. Using the EF 25 tube is a simple way to enable close-ups at high magnifications. The magnification depends on the prime lens used. With a standard zoom lens, the EF 25 can give a magnification of 0.7x or higher. Although autoexposure is possible, manual focusing or using the focus aid in your EOS cameras is recommended. Basically, there are no techniques in shooting pictures using your EOS cameras with the EF 25 Extension tube attached other than the recommended use of a tripod whenever you are shooting close-ups outdoors. Depth of field in close-up shootings may be shallower hence it is necessary to stop down the aperture to obtain maximum depth of sharpness. If you are shooting with strobes like the Canon Macro Ring Lite ML-3 or any of the Canon EZ or EX series of Speedlites, it is okay to try hand-held shooting for your close-ups photography using the Extension tube. << Back to Main . 1 . 2 . 3 . 4 .