Nikon D800 Raw Image Quality
We used to convert raw files used for comparison crops with dcraw (an excellent freeware raw converter), as we could count on dcraw not to apply any noise reduction, sharpening or other corrections. Lately, though, we've switched to Adobe Camera Raw with its noise reduction and sharpening options set to zero. We've found conversions made with recent versions of ACR to be almost identical to dcraw when dcraw's demosaicing option is set to match ACR's method, so we're pretty sure ACR isn't applying any noise reduction "under the hood" like it used to.
Below are crops from Nikon D800 raw files compared to raw files from other high-resolution full-frame SLRs:
Here, we can see the 16-megapixel Nikon D4 performs the best in terms of noise at higher ISOs. That's no surprise, though, given it has the largest photosites of this group (pixel pitch of 7.3 microns versus 4.8 for the D800 ). We've included it here as it's arguably still the current high ISO king. Next would be the 22-megapixel Canon 5D Mark III, with its 6.1 micron pixel pitch. The 36-megapixel D800 comes in third, but keep in mind its resolution advantage is significant. If you resample the D800's images down to the others, you may be surprised how well it compares. The 24-megapixel Sony A99 comes in fourth here with its 5.9 micron pixels, likely handicapped somewhat by its light-robbing semi-transparent mirror.