Only certain Canon lenses are compatible with the Canon EF 1.4x II Extender. As a rule, but subject to change, the compatible lenses include fixed focal length L lenses 135mm and longer, zoom L lenses at least 70mm on their wide end and Canon TS-E Tilt-Shift lenses. Shop for canon extender ef 1.4 x ii at Best Buy. Find low everyday prices and buy online for delivery or in-store pick-up In reply to BG454 • Mar 13, 2014. MisterBG wrote: I'm considering a 1.4x teleconvertor and I was looking for opinions and comments on the Canon EF 1.4 MkIII against the Kenko 300 DGX. Most use will be for wildlife, including BIF, and principally with the 70-200 F4L and 100-400 F4.5-F5.6L lenses on my 6D body. I'd suggest getting the 1.4II. The difference between the II and III is quite small as other's have pointed out and you'll be saving a fair amount of money especially if you pickup one a used one. The 2xIII works nicely on the 70-200II however focusing speed is reduced by 50% so be aware of that. 1. They don't fit. The adapters have a rectangular baffle inside that the RF protruding front element does not fit within. subtraho's gear list: Canon EOS R5 Canon EF 100mm F2.8L Macro IS USM Canon EF 500mm f/4.0L IS II USM Canon RF 24-105mm F4L IS USM Canon RF 100-500mm F4.5-7.1L IS USM +7 more. Reply Reply with quote Reply to thread Complain. EF 28-90mm f/4-5.6 II : EF 28-90mm f/4-5.6 III : You can also correct RAW images taken with the compatible lens even when the extender is attached. Options. 05-13-2023 06:35 PM. I did some testing today comparing the Sigma 150-600 C to the RF100-500 +1.4x extender. With both lenses zoomed all the way (600mm and 700mm respectively). I set the Sigma lens at F/8 and the Canon at F/10, at 1/1000. I adjusted the ISO to compensate for the Canon's smaller aperture. Re: Canon 7D Mark II, 100-400II lens and 1.4III extender In reply to PK62 • Jul 26, 2018 I just ordered a Tamron 1.4 Pro converter from Adorama for my Tamron 100-400 and Canon 7D MKII and after connecting the converter to the lens and then to the camera body, I get a firmware update warning. Adding a tele extender does not change the focal length of that lens. The thing that does change is the angle of acceptance. The focal point of that lens does not change and can not change. Also any time you increase the length of the lens tube, you will sacrifice some f-stop value. Adding the 1.4x to your 400mm lens dose not turn it into a Professional grade bodies have AF points that can still focus with a lens that has an effective maximum aperture of f/8. Using a 2x teleconverter with the 100-400 will create a lens with an effective aperture that varies from f/9 to f/11. In other words, you will definitely lose the ability to AF through the viewfinder. 7sFI.