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 higher sensitivities. As you can see from the crops below all of the cameras use a combination of reduced sharpening and/or noise reduction. The cleanest image with the most retained detail is from the Nikon D50 closely followed by the Canon EOS 350D and the Nikon D70s. While the EOS 300D image looks cleaner in the lighter area of the image (the 'signal') more noise is visible in shadows.

Nikon D50, ISO 1600
Nikon D70s, ISO 1600
Pentax *ist DS, ISO 1600
Canon EOS 300D (Digital Rebel), ISO 1600
Canon EOS 350D (Digital Rebel XT), ISO 1600