Canon 1D Mark IV High ISO RAW
Canon EOS-1D Mark I RAW Image Quality
We've recently started looking at RAW files converted with draw, an excellent fearer raw converter. draw 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 NOR 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 demolishing algorithms they use (the processes by which they convert the separate Red, Green, and Blue data sets to an array of full-color ROB pixels), but draw 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 and higher examples below, it's clear that draw's demolishing approach does have some tendency to produce rectilinear artifacts in response to high noise levels.)
Below are crops from Canon 1D Mark IV RAW files compared to RAW files from pro grade digital SLRs, converted with draw.
Looking at the crops above, the Canon 1D Mark IV does show an improvement over its predecessor, at least at ISO 3,200 and 6,400. That's quite remarkable, given 1D Mark IV's 5.7µm photosites are quite a bit smaller than the 7.2µm photosites of the 10-megapixel 1D Mark III. This is real progress.
It's clear however that the Nikon D3S is still the high ISO champ, which is no surprise since the Nikon D3S's 8.5µm photosites are quite a bit larger. With only about 15% higher linear resolution, resampling the 1D Mark IV's slightly larger 16-megapixel images down to the D3S's 12-megapixels to reduce noise won't come close to making up for the difference in high ISO performance. The Nikon D3S clearly outclasses the Canon 1D Mark IV in this respect.
The Canon 1D Mark IV does quite well against the 24.5-megapixel Nikon D3X in terms of noise, but the later has quite a resolution advantage.