Based on the in-camera JPEGs, it seems to me that the G12 is about two stops better than the G6 with respect to noise. But then I began to wonder if this apparent difference was actually due to noise reduction software in the G12. To test this hypothesis, I took another look at those images but this time from the RAW image files.
The above 100% crops (click to see full size) were processed from the RAW files using Adobe Camera Raw. The G12 profile for ACR is still a “beta” but is probably representative. Processing for both the G6 and G12 was as follows:
... as shot auto white balance
... auto toning
... medium contrast curve
... ACR sharpening at 80%, 1 radius, 30 detail, 60 mask
... 0 noise reduction in ACR
... default noise processing in Noiseware Pro.
This time I skipped the G12 ISO 800 and used ISO 1600 and 3200. The G6 ISO 400 image cleaned up nicely but the G12 still has less noise – I think about two stops improvement but perhaps only 1-1/2 stops.