See:-
http://informationondigitalcamera.blogspot.com/2009/10/pentax-k-x-night-shots-at-iso6400.html
(Source: http://www.flickr.com/photos/heartlogic/sets/72157622494864286/ (with other samples taken at lower ISO speeds))
Download the full size images if you want to measurbate (forever and endlessly! ;-p)
Happy measurbation!
Well, once again, it seems that the ISO 6400 IQ and noise level is somehow close to that of the ISO 1600 of the K-m of which the IQ is yet better than that of the K-7 at just ISO 800. I think I have to say a "Well Done!" to Pentax this time but at the same time, they should consider to replace the sensor in the K-7 and give us a revised and updated model of it soonest! Is it actually logical to have an entry level model to outperform their own "flagship" in IQ like this??