The extender comes with a compatibility chart which essentially lists all of Canon's posher telephoto primes and zooms from 135mm f/2 up. Extenders also multiply the f-stop. The 135mm f/2 becomes a 270mm f/4, the 70-200mm f/4 becomes a 140-400mm f/8. The 2x extender lost 6 f-stops with this configuration, the camera wouldn't go wider than f11 vs. f5.6 normally. Check other reviews and tech specs - I thought it wouldn't be as many f-stops so maybe this was something to do with the body I was using. Here’s a chart showing the Canon lenses that are compatible with the Yongnuo teleconverter: Like the recently launched Canon 50mm f/1.8 clone, Yongnuo’s version appears to have pretty decent Type of extender: AF availability: EXTENDER EF 1.4x: When any of the extenders shown to the left are mounted on a lens with a maximum aperture darker than F4, AF cannot be used. EXTENDER EF 1.4x II: EXTENDER EF 1.4x III: EXTENDER EF 2x: When any of the extenders shown to the left are mounted on a lens with a maximum aperture darker than F2.8 Currently, this teleconverter can be picked up for around £275, which isn’t quite bargain-basement territory, but is still less expensive than Canon’s EF Extender 2x III, which costs £300 The Canon EF 100-400mm f/4.5-5.6L IS II USM Lens is compatible with the Canon EF 1.4x III and EF 2x III Extenders. As is often the case, the focal length range of the with-extenders combinations is quite impressive with relatively little increase in size and weight. Extender EF 1.4x III – 72 x 27.2 225 Extender Cap E II – LP811 – – – – – – Extender EF –2x III 72 x 52.7 325 Extender Cap E II – LP811 – – – – – – EF ZOOM LENSES EF 8–15mm f/4L Fisheye USM Filter Holder 78.5 x 83 540 Lens Cap 8‐15 EW‐77 (15mm only LP1219 – – – ‐ – rGTbC.

canon extender ef 2x iii compatibility chart