The crops below are taken from the originals, saved as High Quality JPEGs in Photoshop CS2 and presented here at 100%. To compare typical noise in skies and dark shadows the crops were taken from patches 3 and 24 respectively.

Noise levels on the Canon 5D are low up to 800 ISO, and even at 1600 ISO remain very usable. Interestingly though, when examined at 100 percent, there’s a rougher pattern visible at lower sensitivities compared to the silky smooth results of the 1Ds Mark II.

This is slightly disappointing considering the 5D has a slightly larger pixel pitch than the 1Ds Mark II and we’d actually hoped noise levels might be a little lower as a consequence. We’re being very picky here though because overall noise performance on the 5D is, like other Canon DSLRs, excellent, and you’d have to be a very fussy pixel-peeper to worry about the effect described.

Compared to the cropped sensors of their rivals though, the results from the 5D and 1Ds Mark II clearly illustrate the benefit of having a physically larger full-frame sensor with a subsequently greater pixel pitch. Noise levels from these bodies are much lower throughout, although especially so at 800 ISO and above.