None, but you can't do it the other way around.
?? You can on Nikons
As to the OP, the main issue is you lose a load of pixels, as in the DX lens is focusing on the centre part of the sensor, you loise the edge. I am sure one of the techies can explain it better though
Nikon FX bodies sense when a DX lens is fitted and crop the sensor to suit, Canon EFs lenses wont fit EF bodies, You can only use EF lenses on Canon FF Bodies so the same senario dosnt apply.
Nikon FX bodies sense when a DX lens is fitted and crop the sensor to suit, Canon EFs lenses wont fit EF bodies, You can only use EF lenses on Canon FF Bodies so the same senario dosnt apply.
No, you can use EF lenses on crop and FF bodies. When used on crop bodies you don't lose or gain anything, pixel wise. You can only use EFS lenses on crop bodies & not FF.