Now we see through a glass, darkly...
- Apr 5, 2016
I'm struggling with the idea of an RF-S lens. The distance to the sensor from the bayonet would still have to be the same as the RF lens, since the mount/sensor relationship is the same as you'd need in order to maintain compatibility with the full frame lenses. I suppose the rear glass could still come in to the body farther on account of needing a smaller image circle. It would even still mount on a FF variant although it wouldn't cover the whole sensor. I guess you'd be somewhat limited in the size savings as the RF mount is bigger than the EF mount, so the smallest RF lens will still be bigger. But maybe it could work as an ecosystem. Will be exciting to see.
RF and EF have the exact same 54mm throat diameter. EF-M is smaller at 47mm.