Compared to...

Studio scene comparison (higher sensitivities)

In compact cameras we've had to watch the manufacturers trying to pack more pixels onto their sensors while also offering higher sensitivity modes, blithely ignoring the inherent conflict between the two demands. The Pentax's relatively densely packed (for a DSLR) sensor made us wonder if the same was going to happen here too. In spite of the increased resolution, the K20D's default highest ISO setting is one stop higher than the K10D.

We needn't have been so concerned, as the K20D keeps up with the best performers right up to its highest default setting of ISO 3200. Pentax seems to have taken a slightly odd approach to noise reduction that allows quite a lot of chroma (color) noise to remain in the image, but the results aren't unpleasant.

If you change custom setting 4, the K20D will shoot at up to ISO 6400 at which point it comes a little unstuck and you can see as much noise and aberrant information as actual detail (and this is a scene shot in good light with a fairly balanced spectrum, which is about as easy as these things get). It's not a great performance but there are few cameras that do well at such sensitivity levels and Pentax probably deserves some credit for making it clear that ISO 6400 is pushing things a bit. (We suspect it's not a 'true' sensitivity setting, achieved at a sensor level, but a mathematical attempt to 'push' the ISO 3200 results).

The K20D has four levels of high-ISO noise reduction that can be applied: off, weakest, weak and strong. The ISO 800 and 1600 images were shot with NR turned off (the default). However, the camera turns noise reduction up to 'Strong' at ISO 3200 and greater.

ISO 800

Pentax K20D Sony DSLR-A700
Olympus E-3 Canon EOS 450D / XSi

ISO 1600

Pentax K20D Sony DSLR-A700
Olympus E-3 Canon EOS 450D / XSi

ISO 3200

Pentax K20D Sony DSLR-A700
 
Olympus E-3  

ISO 6400

Pentax K20D Sony DSLR-A700