Canon 7D in Sea & Sea 5D MK II Housing

a crop frame camera will have essentially the same depth of field at f11 as a full frame camera at f16 and diffraction severly reduces resolution beyond those apertures in both cases. the crop frame camera has greater "magnification" but i find no noticeable difference between a 40D image and crop from 5D2. i would be very happy to buy a 7D if there is a noticeble difference in resolution between it and a crop from the 5D2 -- but have not found a comparison

A 5dmk2 image (as glorious as it is) cropped to the frame size of a 7D yields only 8+MP, so half what a 7D can do. No, some of that can be compensated UW depending on your lens and camera to subject distance, but given same distance and subject matter and that the photographer can take a sharp image with either body... there will be more detail on the 7D image.

DOF issues have been hashed to death, but if I need more DOF for the subject, I will have no qualms in cranking the aperture down past (if so) the diffraction limit to get more of the critter in focus.

I've also found that 7D images require quite a bit more sharpening in Post than 5dmk2 images.

My 2 cents

S.