Olympus E-M5 RAW Comparison
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. Unfortunately, dcraw's author has not been providing timely updates lately, so we have switched to using 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."
See crops below to compare the Olympus E-M5's (12-bit) RAW image quality to its sibling, as well as a few recent, premium compact system cameras.
As you can see, the Olympus E-M5 does very well against this group, producing RAW files with the lowest noise. The improvement over the 12-megapixel E-P3 is striking at higher ISOs, despite the E-M5's smaller photosites. The E-M5 also does better than the 16-megapixel Panasonic G3 and the 20-megapixel Samsung NX200. Excellent performance, though contrast in the red leaf swatch is a little low.
Here's a comparison with some premium APS-C models.
The Fuji X-Pro1 Adobe Camera Raw conversions are by far the cleanest here, but they look as if some filtering has been applied, spreading out chroma noise and attenuating luminance noise while reducing acuity in the process. We're not sure if this is a deliberate attempt at noise reduction (something we don't like to see in RAW files), or just a by-product of the interpolation algorithm needed to demosaic the X-Pro1's unique 6x6 filter array.
The Olympus E-M5 compares favorably to the cameras using conventional sensors, producing noise levels that are pretty much on par with the 16-megapixel Nikon D7000 and slightly better than the 18-megapixel Canon 7D. That's a remarkable achievement considering the E-M5's pixel pitch is significantly smaller than both, at about 3.7µm versus 4.7µm for the D7000 and 4.2µm for the 7D.