PRODUCT INFO. Max. Diameter x Length, Weight. This lens is only compatible with fixed focal length L-series lenses 135mm and over, as well as the EF 70-200/2.8L, EF 70-200/2.8L IS, EF 70-200/4L, and EF 100-400/4.5-5.6L. Additionally, please see the lens and/or camera body manual for full compatibility information with the Extender EF 2X III. Versatile 70-200mm zoom range. 3.5-stop Image Stabilizer. USM autofocus. f/2.8-32 aperture range. 1.2m closest focus. Sealed against dust and moisture. 8-bladed diaphragm. Weight: 1480g, Dia x length: 88.8x199mm. The 70-200 f/2.8L IS II is compatible with the Canon Extender EF 1.4x III and Canon Extender EF 2x III as shown above. I generally recommend buying a lens with the focal lengths you need natively in them - they usually provide better image quality and focus speed. Here's a video comparison between the Canon 70-200mm 2.8 II USM with and without the Canon 2x III Extender on a Canon 5D Mark iii. Footage shows fully zoomed I have two APS-C (70D and 600D) bodies with Canon EF and EF-s lenses, and Sigmas, among them the Sigma 70-200 f2.8 HSM OS. I am also considering getting the new Tamron 150-600 lens, pending reviews. I was just curious if a Canon extender, specifically the canon EF 2X III, will work on the Tamron and/or Sigma lenses. Hi Carla, and welcome to the forum: At this stage I am assuming you do not want to pay for native RF long telephoto lenses, given their high cost and that's why you are looking at extenders, which are themselves not cheap. I have used the EF 70-200 MkII IS USM (f/2.8 and f/4 units) with the R6, but I have been using the 1.4x extender with various models of the 70-200 f/2.8 along with other telephotos for 25 years. I love the 1.4x and hate the 2x. I have seen almost negligible change to an image with the 1.4x on an L lens and no difference in autofocus speed. The 2x is noticeably soft and the focus slows way down. "Teleconverters are one of those things people buy when they first start in photography because they sound like a neat idea." So true. I would try the cropping Canon EF 70-200mm F/2.8 L IS II USM Lens & Canon ef extender 2x iii Before and after test. No post production to footage. Camera Used is Canon 70D. This is j The 1.4x TC drops the maximum aperture from f/4 to f/5.6, and the 2x TC drops it to f/8. The good news is that on your 7D the 1.4x TX gives you the angle-of-view equivalent to a focal length of nearly 450mm on a full frame camera, which is fine for a lot of wildlife shooting. Dan. u5rg.