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 and 1600. As you can see from the crops below all of the cameras use a combination of reduced sharpening and/or noise reduction, more detail is visible especially in the ISO 800 shots for all of the Canon cameras. The cleanest ISO 1600 image is delivered by the EOS 20D, closely followed by the EOS 300D and 350D. The E-300's noise and loss of detail is higher than the rest.

ISO 800
ISO 1600
Canon EOS 350D
Olympus E-300
Canon EOS 20D
Canon EOS 300D