Originally Posted by
Wayne Niz
Hi Dorian,
If I may offer some advice (although please be aware im a complete newbie). I have the R5 and R6 and use EF lenses with the adapter. This combination works seamlessly, I have the 70-200 2.8l ii, 100-400L ii, 600 4l ii and use the TC 1.4 iii and TC 2 iii with these lenses (in fact I have even stacked the 1.4 and the 2 with an extension tube on my 600 and still had perfect autofocus). I also have Sigma EF lenses 105 1.4, 50 1.4, 24-32 1.8 and the 70 2.8 macro, every one of them work perfectly. So while making your choice in my view compatibility on EF lenses on the RF mount is not a concern. In fact its an advantage because you can get the equivalent EF lenses much cheaper...
Good luck