Sony DSLR-A500 Raw Comparison
Sony A500 High ISO 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 demosaicing 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.
Below are crops from Sony A500 files compared to RAW files from a few competing models. All were converted with dcraw with no noise reduction or sharpening.
In the above crops, we can see the Sony A500's noise performance is competitive with sensors from the other APS-C cameras in this group, and better than the smaller Four-Thirds sensor found in the Olympus E-620. Click on the crops above to load the full size images.