Compared to...

Studio scene comparison (higher sensitivity)

As well as shooting our studio test scene at each camera's lowest sensitivity we also shot it at ISO 800 (or the maximum). As you can see in the 100% crops shown below the *ist DS manages to keep noise levels low although we can see a little noise on the left side of this crop (shadow area). What noise reduction is used by the *ist DS is kept to a minimum and there's about as much image detail here as we saw at lower sensitivities.

Pentax *ist DS, ISO 800
Canon EOS 300D, ISO 800
Nikon D70, ISO 800