Canon EF 1.4x Extender. £176.99. Click & Collect. Free postage. or Best Offer. Only 1 left. Canon Extender FD 1.4x A Teleconverter for Telephoto FD lenses. St no u16752. £94.99. I wouldn't do it. It's already a slow lens and the tele-con will only make it slower f9 to f14 in the case of the 2x. Very slow starting apertures! Since I wouldn't do it, I don't know if they work or not personally. Canon tel-cons do not work on all Canon lenses. Make sure the Rf 100-500 is listed The 100-500L works amazingly well with the RF 1.4x converter. I was never a huge fan of the EF converters, and I preferred not to use them unless it was necessary. However, the RF converters have completely reversed my previous thoughts. When I'm out shooting wildlife I'll have the 1.4x on more often then not. Canon's EF Extenders . Without an Extender attached, the Canon 200mm ƒ/2.8 II USM lens shows very good results at ƒ/2.8, becoming almost tack-sharp at ƒ/4 through to ƒ/11. EF (full-frame) lenses have a red dot, EF-S (APS-C sensor) lenses have a white dot. The EF-S lenses extend further into the camera body so will NOT mount to an EF TC. I have no problems mounting the Sigma 1.4 and 2.0 TCs to my (EF mount) Sigma 70-200 2.8 for use on my 500D but the TCs are useless on my (EF-S) kit lenses and my 60mm macro. Canon Extender EF 1.4x III. Extends the master lens focal length by 1.4x. Outstanding image quality. Highly resistant to dust and water. £ 479.99. Eligible for free delivery. The T CINE Speed Booster ULTRA 0.71x Adapter from Metabones allows a Canon EF-mount lens to be mounted onto a camera with a FUJIFILM X-mount. The adapter's optics maximize the connected lens's apparent angle of view by a factor of 0.71x while providing a one-stop increase for the camera over the lens's aperture range. More Details. Article ID: ART174705 | Date published: 06/07/2019 | Date last updated: 06/10/2019 Description These lenses can be used with either the Extender EF1.4X III or the EF2X III. Solution Usable lenses: *: Using an Extender with this lens may result in incorrect autofocus. If your camera has an AF microadjustment function, do the AF microadjustment. Even with a 1.4X TC III its image quality is on par with the best Sigma and Tamron have to offer, and without a TC its image quality is unmatched, except by the EF 70-200 f/2.8L IS II. Add to that a short minimum focus distance and the EF 100-400 L IS II is the best lens in the 100-560mm range. I think you would be better off with the RF 800mm prime compared to the 100-500 with a teleconverter. The prime would focus faster and more accurately. For that price I would take the f/11 fixed aperture.. With either setup, your available AF points will no longer cover edge to edge. You will probab vTQIIbB.