[leepsj]

Is there any problem with the camera's operation when there are a scratch or two on the metal mount of the camera ?

How could I avoid scratching the mount when replacing the lenses ?

[eos1dmark2]

These cosmetic imperfections won't affect the proper operation at all. Just be careful when mounting or dismounting the lens. Somehow, some scratches will appear no matter how careful you are... :)

[leepsj]

Do u mean even for higher end DSLR, scratches on the mount is normal and hard to be overcome ?

[eos1dmark2]

Yes, high end DSLRs (e.g. Canon EOS 1D series)'s lens mount is made from the same material (stainless steel) that will be scratched eventually.

[leepsj]

If I change the lenses without turning off the dslr (but it is in powersaving mode), is there any problem after that ?

[eos1dmark2]

No problem even the camera is on (my experience), I bet the manufacturers should have taken this into account when designing the camera.