Comparing the old and new gives us the chance to see how Pentax have improved their sensor technology since early 2011.
Looking at the Q10 relative to the Q, we can see that the Portrait score is a little better on the newer camera (21.1bits vs 20.2bits, a difference of 2/3rd stop) which is what has accounted for the fractional improvement in overall DxOMark score.
Disappointingly, both the landscape score and the sports score actually show a fractional step backwards although it is not sufficient to be a major concern. If the Q10 was not around $300 cheaper than the Q, there would be little reason to pick the new camera over the old model from an image quality point of view.
One interesting point to note is that Pentax have applied a noise reduction algorithm to the RAW files as well as to JPEG files from the camera, essentially smoothing out the image to try and make up for poor ISO performance from the small sensor.
Between these two models, the Q10 comes out on top in the portrait test, scoring 21.2bits to the J3’s 20.4bits, a difference of 1/2stop. In the dynamic range test, the differences are so minimal as to be insignificant. It’s the sports test that really shows the benefit of the larger sensor, as the J3 scores 420ISO, more than 1stop better than the Q10’s 183ISO.
If you’re comparing these two models, then unless you are drawn to the smaller size of the Q10, or you plan to shoot lots of portraits and want the better colour depth, then the Nikon 1 J3 is most likely to be the better choice.
Against the GF5, the Q10 comes out on top in colour depth by 1/3rd stop, and by 1 stop in dynamic range, but loses out by 1.65stops in the low light tests.
Comparing it to the E-PM2, shows what is possible within the hybrid arena. The E-PM2 beats the Q10 by a fair margin in all areas – it is 1 stop better in colour depth, 2.3stops better in dynamic range and 2.3stops better in low-light ISO performance. While the Q10 is $100USD cheaper than the E-PM2, it would seem a false economy, especially since the E-PM2 is only 23g heavier than the Q10 (223g vs 200g).