Pentax K-r High ISO RAW
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 6,400 and above examples 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 Pentax K-r 12-bit RAW files compared to RAW files from other consumer SLRs, converted with dcraw.
The crops above compare the Pentax K-r's RAW noise performance to that of other similarly priced consumer models. All cameras were equipped with our Sigma 70mm f/2.8 EX DG Macro reference lenses, stopped down to f/8 for maximum sharpness. As you can see, the Pentax K-r produced RAW files with the lowest noise, though it also has the largest pixels (lowest resolution), giving it a slight edge in light gathering capability per photosite. The K-r also applies some subtle noise reduction at ISOs above 1,600 that can't be disabled, which leads to cleaner images but also to some blurring. The Nikon D5100 comes in second, while the Canon T3i and Sony A560 trail. Very good results from the Pentax K-r, but we'd prefer it didn't apply NR to high ISO RAW files that can't be disabled.
Here's a comparison with the Pentax K-r's predecessor, the K-x, as well as its bigger brother, the K-5.
As you can see, despite the differences in color rendering from dcraw, the Pentax K-r's RAW noise performance is very similar to the K-x. The Pentax K-5 did better than both despite having smaller photosites, though it does appear to have a stronger anti-alias filter which results in slightly lower per-pixel sharpness. But the flip-side of that is reduced moire from the K-5. All three cameras appear to be applying subtle noise reduction above ISO 1,600.