Buy Now by Bryan Carnathan The Canon EF 25mm Extension Tube II is used to allow a lens to focus closer than it does natively. This is accomplished by moving the lens 25mm farther away from the camera body's sensor/film plane by fitting between the camera body and the lens. The end result of focusing closer is a larger magnification . Compare Canon Extension Tube EF 25 II vs Canon Extension Tube EF 12 II vs Tokina AT-X 16-28mm f 2.8 Pro FX Lens for Canon vs Sigma 14-24mm f 2.8 DG HSM Art Lens for Canon EF Press ‎ ↵ Enter ‎ for Accessibility for blind people who use screen readers If you happen to get hold of them, these original EF extension tubes cannot be used with EF-S lenses, but since they have no optical elements they will work with the same EF lenses as the Mark II tubes. The Canon EF12 II and EF25 II Extension Tubes are not compatible with the following lenses: • EF 15mm f/2.8 Fisheye (now discontinued) • EF I never tried the EF extension tube 25 plus EF-RF adapter, but the math should work. Canon RF 100-500mm F4.5-7.1L IS USM Canon G5 X II Canon EOS 70D Canon EOS 7D Compare Canon 77mm 500D Close-up Lens vs Canon Extension Tube EF 25 II vs Canon Extension Tube EF 12 II Compare Canon Extension Tube EF 25 II vs Kenko TELEPLUS HD DGX 1.4x Teleconverter for Canon EF EF-S Lenses vs Kenko TELEPLUS HD pro 1.4x DGX Teleconverter for Canon EF Press ‎ ↵ Enter ‎ for Accessibility for blind people who use screen readers Compare Canon Extension Tube EF 12 II vs Vello Auto Extension Tube Set for Canon EF EF-S Mounts and Lenses V2 vs Canon Extension Tube EF 25 II Also, using a lot of extension, stacking a lot of tubes, such as might be needed with a longer focal length lens, you have to be a bit cautious about the weight of camera and lens, though the Canon tubes (only sold singly in 12mm and 25mm lengths) and the Kenko (set of three, or individually sold) are pretty sturdy with strong latching mechanisms. The difference between the extenders is that the 25 is a 2x, and the 12 is a 1.4x. They give you the option of extending your current lenses effective length, without the higher cost of buying new lenses. By using the extenders, you will lose 1 f-stop with the 1.4x, and 2 f-stops with the 2x. Compare Kenko Auto Extension Tube Set DG 12, 20 & 36mm Tubes for Nikon Digital and Film Cameras vs Canon Extension Tube EF 25 II vs Canon Extension Tube EF 12 II vs Movo Photo AF Macro Extension Tube Set for Canon EOS DSLR Camera yhbALw.