So far, I've only had one session with the RF 100mmL IS USM, maybe 200 shots including same subject shots with the EF 100mmL IS USM using the EOS R5. IQ is comparable but the extra features on the RF version make it more useful to me. IS combined with the R5 is amazing, even at 1.4:1 to 1:1, which is only a close estimate because I shot the majotity hand held, but it was easy to tell distance as I focused at those magnifications because of the range switch. The ring also makes it very useful to me, even though I have a ring adapter for the EF version, the placement of the ring near the front of the RF, in front of the focus ring, makes it more accesible as apposed to being on the ring adaper near the body of the camera when using the EF. A small detail, but it makes a difference. I shot in aperture priority and used the control ring to adjust ISO to get my shutter speed up (I have tremors) as lighting changed. I could have used the dial by my thumb for ISO, but it felt more confortable using the control ring. AF is better and faster than the EF version, and once again, important to me. Lens breathing is moderate and enough to cause problems when focus stacking. It won't concern most, but stackers will have to do some brush up work after the stack is processed. I used a Velbron macro rail on a tripod to set up the stacks and let the R5 take the shots, then processed in Helicon Focus. I never had this problem with the EF, but maybe I got a bad copy of the RF, who knows, everything else seems in order.
I like the lens. It was a good investment for me, and my wife and I won't have to squable over who gets the Macro 🙂
