EOS R7 Comparing RF lenses at similar focal lengths in EF & RF Lenses 11-16-2023; 35mm f2 usm vs 35mm f1.4L? in EF & RF Lenses 11-16-2023; Mount Adapter EF-EOS R question about compatibility with Extender EF 1.4x III in Camera Accessories 11-14-2023; Interesting EF 400 f2.8 IS II issue - EOS-1D X Mark III rendered unresponsive in EF & RF Lenses Mount Adapter EF-EOS R question about compatibility with Extender EF 1.4x III in Camera Accessories 11-14-2023; Interesting EF 400 f2.8 IS II issue - EOS-1D X Mark III rendered unresponsive in EF & RF Lenses 11-12-2023; EF 100-400mm f/4.5-5.6L IS II USM Lens switches to MF mid shoot in EF & RF Lenses 11-10-2023 wrote: The Canon EF 70-300mm DO USM manual says it will not work with the EF 2X II extender. Will it work (particularly the IS) with the newer EF 2X III extender? thanks Jerry No, it will most likely not be fully compatible with that lens. Check the compatibility chart. (Max. dia. × length): EF1.4X III: 72.0 dia. × 27.2 mm / 2.8 × 1.1 inch EF2X III: 72.0 dia. × 52.7 mm / 2.8 × 2.1 inch Weight: EF1.4X III: approx. 225 g / 7.9 oz, EF2X III: approx. 325 g / 11.5 oz Case: EF1.4X III/EF2X III: LP811 * All specifications are based on Canon's tests and measurements. EOS-1Ds Mark III: EOS-1D Mark III: EF 14mm f/2.8L USM: You can also correct RAW images taken with the compatible lens even when the extender is attached. 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 – – – ‐ – azpyDm. EF1.4X III: EF2X III: EF 135mm f/2L USM: 189mm f/2.8: 270mm f/4: EF 180mm f/3.5L Macro USM: 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. Since some of the optics of the Canon 1.4X and 2X extenders extend into the back of the lens attached to them, they are only compatible with specific lenses. No EF-S lenses are compatible with any version of the Canon Extenders. Here is a link to the list of Canon lenses compatible with Canon extenders. Note that the only lenses with focal EOS-1Ds Mark III: EOS-1D Mark III: EF 14mm f/2.8L USM: You can also correct RAW images taken with the compatible lens even when the extender is attached.

canon extender ef 2x iii compatibility chart