Takes practice. The cap has a groove. The red mark on all RF lenses is on the silver/gunmetal RF mount next to the black plastic groove. It's possible to get it wrong by 180 degrees though. The key is that the red groove is on the same side as the AF/MF switch.
This is true on all my RF lenses. 28-70 f2, 24-105 f4, 35 f1.8, 50 f1.2, 700-200 f2.8. I suspect it is on the rest too. Can look it up web page pix.
For the EF/RF adaptor, the red mark is next to the EF lens release switch.
After a few practice it gets easy and you don't have to look. Just grab the lens with the AF/MF switch side matching the cap groove.
Aug 06, 2020 at 10:34 PM
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