Canon EF Extender 1.4x II. Palm, 19 December 2014. Canon 5D Mark III, Canon EF 300mm f/4 L with Canon EF Extender 1.4x II at f/5.6 (wide open) at 1/640 hand-held at ISO 100, no lens profile used, Athentech Perfectly Clear v2.) Full resolution. It works well with the Canon EF Extender 1.4x II, making it a 420mm f/5.6. I was thinking of purchasing either a 1.4x extender or a 2x extender for my Canon EF 300mm F4 to get more close up shots of nebulae. I was wondering how the star adventurer would hold up at this focal length with an autoguider and if I could get decent shots up to 2 minutes with it. Thanks! I shoot with the same lens and a 1.4TC. The Canon 100-400mm Mk II is also compatible with the Canon 1.4x extender, though it will only autofocus on higher-end Canon DSLRs that retain AF up to F8 (currently 7D Mk II, 5D Mk III, 5DS/R, 1DX/II). The 2x extender will physically fit, but all AF functions are disabled. Canon EF 100-400mm f/4.5-5.6L IS USM Canon EOS 5D Mark III Canon Extender EF 2x III If you believe there are incorrect tags, please send us this post using our feedback form . Here is a link to some samples of mine using the Sigma 150-500mm Sport with the Canon 1.4x III converter on the R5. The autofocus with this combination works much better on the R5 than it does on my 5D IV or 7D II. Bob. Canon R-5: Rahto: Galleries: Digital Photography Review : Digital Photography Review (dpreview.com) Learn more with 3 Questions and 4 Answers for Canon - Extender EF 2x III Extender Lens - Multi. User rating, 4.9 out of 5 stars with 5130 reviews. (5,130) "Hello, My Name is Gene Simmons" EOS 1D X, EF 600mm f/4 L IS II + EF 2x III Extender, 1/2500 s, I use the 2x extender quite often on the 600mm Canon II. And yes I was pleasantly surprised. At 19m distance from the charts, the RF 2x performs far better on the 100-500mm than does the EF 2xTC on the 100-400mm II. The 100-500mm at 1000mm produced crisp lines, and gave 40% more resolution than the bare lens and about 20% more than the 100-500mm at 700mm. Tested with EF 2X III and 1.4X III on both Canon EOS M50 and Canon EOS RP. Interesting finding. (1) The TC fits (although the gap is much lesser than Canon lenses at the mount end). (2) Interesting finding: EF 1.4X III with Tamron 100-400mm shows F value of F13 while 2X shows F9. Both cameras show this behaviour. Canon EF 2X III Extender | Review & Overview. David Santiago. 255 subscribers. Subscribe. 9.3K views 1 year ago. A concise review and overview of the Canon EF 2X III lLVfq.