Just a couple of ISO 6400 examples, no artistic merit attempted
Taken in dim light, High ISO NR off. Exif still intact - f/4.0 (Slow lens DA 50-200mm) and shutter 1/40 secs.
I don't quite like the noise in the dark areas, but it looks quite OK in the well-exposed areas.
100% Crop - a lot of detail still in the photo, but the noise is very obvious.
Just as an aside, I had never found the DA 50-200mm to be a good low-light lens, but thanks to the K-7 fast low-light AF , excellent AWB and good High-ISO handling, its now quite usable in low-light.