« on: October 18, 2013, 05:53:36 PM »
The Next Question = For use the EF to EF-M Adaptor, Yes, We can use both EF and EF-S mount to this Adaptor and shoot with EOS-M----How can We use EF-S with the same space distant from the back of EF-S lens to the APS-C sensor, and work---BUT Can not mount EF-S Lens on Full Frame Sensor Canon EOS Cameras----In the reverse, We can use all EF Lenses on the SOS Body / Small sensor like 7 D .EF-S has an identical 44 mm flange distance to EF. However, EF-S lenses are specifically designed to create an imaging circle which is not big enough for a 36x24 mm frame. In a bid to prevent strong mechanical vignetting, EF-S lenses have a plastic bung at the back preventing mounting on an EF mount body. This has a second advantage - these lenses can be designed to poke deeper into the body into the area where the larger FF mirror would otherwise clash, allowing some wide angle EF-S lenses to be slightly less retrofocus than the same focal length FF lens would be.
??, May be, Canon try to trick us, Not let us use the cheap FE-S Lens on the high cost FF Cameras .
I have tried my Canon EF-S 10-22 on my 5D mk II - I had to pull the bung out of the back of the lens, and as long as the lens is zoomed into about 12mm or longer the mirror doesn't hit. From about 13mm onwards, with no filter there's no mechanical vignetting, and at no focal length or aperture is the corner performance anything but beyond a joke.
EF-M has an identical sized sensor to EF-S bodies, but due to the lack of mirror the flange distance is just 18 mm. All that's needed to make an EF-S lens fit then is a 26 mm long spacer with the appropriate mount at either end. The sensor size and position relative to the lens is then identical to an EF-S body. The adaptor also takes EF lenses, in much the same way as an EF-S body does.