Here is a comparison of the same night scene shot with both the K-3 and K-5 with similar ISO, Aperture. I did this to test the K-3 Improvement over my existing K-5 after I got it a couple of weeks ago. Not only is the noise levels better on the K-3, you also have to consider that if the K-3 24 MP images are resized to the K-5 16 MP size, when the images are resized to 16 MP. See the comparison for yourself. All are 100% crops from the raw images. My focusing was a bit off on the K-3 because it was a manual lens and shot in the dark, Samyang 16mm F2, the aperture for all the shots was f 2.8 and just checked now, the shutter speeds were different, but everything else was the same. That could be what made the difference as i had the shutter automatically metered. Also you might find the K-3 Images are not as focused as the K-5, but thats my manual error. I also did not shoot beyond 6400, so I have no samples at ISO 12800 and ISO 25600 or 51200
This is how dark it was for the actual scene..
---------- Post added 12-16-15 at 09:26 AM ----------
Also here is another indoor shot at ISO 3200 on the K-3 and its 100% crops, the white balance is off, please forgive me.
crops