Canon 5D Mark II RAW Image Quality
We've recently started looking at RAW files converted with dcraw, an excellent freeware raw converter. dcraw usually offers timely support for the latest cameras, but more importantly, it does not apply any noise-reduction, sharpening or other corrections such as geometric distortion correction to the output files. (We found that Adobe Camera Raw still applies some limited noise-reduction when its NR settings are set to zero, and it also applies other corrections depending on the make and model of the camera). There will always be differences between RAW converters, in terms of the sort of de-mosaicing algorithms they use (the processes by which they convert the separate Red, Green, and Blue data sets to an array of full-color RGB pixels), but dcraw seems to use a fairly generic algorithm that delivers good sharpness with relatively few artifacts, and can be counted on to not apply any noise reduction if you don't want it to. (That said, looking at the ISO 25,600 example from the 5D Mark II below, it's clear that dcraw's de-mosaicing approach does have some tendency to produce rectilinear artifacts in response to high noise levels.)
Below are crops from Canon 5D Mark II RAW files compared to RAW files from other 21+ megapixel digital SLRs, converted with dcraw.
The crops above compare the Canon 5D Mark II's RAW noise performance to that of the Canon 1Ds Mark III, Nikon D3X and Sony A900, across their entire ISO ranges. Noise levels from the four cameras are pretty similar up to and including ISO 400. At ISO 800, we see the two Canons and the Nikon pull away from the Sony by just a hair. At ISO 1600 and above, the Sony appears to be behind the others by roughly a full stop in terms of noise.
Some of you are no doubt wondering if the Canon EOS 5D Mark II has dethroned the Nikon D3 and D700 as the high ISO kings. In the table below, we compare high ISO crops from Canon 5D Mark II RAW files resized to 12-megapixels as well as 5D Mark II sRAW1 crops (10-megapixels), to Nikon D3 and D700 (12-megapixels) RAW file crops.
To our eyes, the Nikon D3 and D700 still have superior high ISO performance, though the Canon 5D Mark II does amazingly well considering the smaller pixel size. The Canon 5D Mark II's sRAW1 files are cleaner than its full sized files, but they don't contain as much detail as resized 5D Mark II full-res RAW files, or the Nikon D3 or D700 RAW files. They seem to have either have some NR applied, or the interpolation process used to generate the smaller files is causing loss of fine detail and larger chroma noise blotches.