This is driving me nuts, have spent hours attempting to resolve, and several calls with Canon support. So I have new lens (EF 600mm f4L III) that I am attempting to register on the Canon site while in my account. I enter the product, ser. #, etc, th...
I have both the EF 600mm f/4L IS USM III and the 1.4x TC III. I use the lens with my R5 with EF/RF adaptor. I have no need to use 1.4x on a 600mm, espeically with a 45mp camera and using the 1.8x crop mode (which entails no change in my f stop); ho...