I just bought a 5D mark III. Am I correct that EF-s Lenses will not work?

[cicopo]

DO NOT try any EF-S lenses on it. The mirror will hit them when you take a photo & that might result in breaking the mirror. You can however use non Canon brand lenses designed for the crop bodies that DON'T have anything mounted on the body end of them (that would stick into the mirror area) BUT most won't provide a full image. They will have either the corners blacked out or look as though you shot through a pipe. 

[p4pictures]

Correct, you can't use the EF-S lenses. Most EF-S lenses extend further in to the mirror box and actually you have to be pretty ham fisted to even get an EF-S lens to mount on a full-frame camera body.

That said I do have a picture somewhere that was taken with an EOS-1Ds Mark II (full-frame) and shows that the EF-S 18-55mm kit lens off a rebel was used in the EXIF, what it doesn't show is that an EF-12 II extension tube was also used 🙂 

Brian

[Samsen · Accepted solution]

Bayonet in EFs is slightly different from EF so physically it WILL NOT fit your full frame body.

[ebiggs1]

Yeah, I don't think it will even mount. I am not going to try it but the dots for alignment are not in the same place.

[Samsen]

That has to do with the way bayonet is arranged to fit.

Also check for the color code.

EF usually Red,

EFs usually White dot.

There is a way to hack the EFs lens to make it EF compatible but I don't advise it to anyone so you didn't hear that from me.