The EOS 5D Mark II's 21 MP sensor means it's beginning to tread on the toes of Canon's flagship professional DSLR, the EOS-1Ds Mark III. Given the huge price difference between the two cameras it will be interesting to see if Canon has managed to match the EOS-1Ds Mark III's image quality in its more affordable little brother.
Studio scene comparison (JPEG)
Canon EOS 5D Mark II vs. Canon EOS-1Ds Mark III
Canon EOS 5D Mark II: Canon EF 85 mm F1.8 lens, Manual exposure,
ISO 100, JPEG Large/Fine, Manual WB, Default Parameters (Standard PS), Self-Timer
Canon EOS-1Ds Mark III: Canon EF 85mm f1.8 USM lens, Aperture Priority, ISO 100 (default base) JPEG Large/Fine, Manual WB, Default Parameters (Standard), Self-Timer
Canon EOS 5D Mark II
Canon EOS-1Ds Mark III
5,607 KB JPEG (5616 x 3744)
5,505 KB JPEG (5616 x 3744)
These two cameras have the same resolution sensor, both full frame, both made by Canon. You would expect the image quality to be very similar, and they are. Apart from slight focus differences caused by the very limited depth of field when shooting this close at F9 on a full frame camera (meaning you have to ignore the top crop and the paper clips when assessing sharpness), the detail and noise levels are indistinguishable. Pretty good for one camera that costs half as much as the other.