http://www.dpreview.com/reviews/canong5/page12.asp
... A quick glance at the noise comparison graph below relates very closely to what we can see on the patches. That is that
Sony's DSC-V1 exhibits the least noise of all the cameras, the Coolpix 5400 is next best and the G5 (even shifted to compensate for its extra sensitivity) has the most noise of the three (from ISO 100 upwards). I was quite surprised to see this, clearly the competition have caught and overtaken Canon in this respect.
One thing that's quite noticeable looking at the full color crops above is that
Sony keep color balance under control throughout the sensitivity range, the Nikon crops for instance get progressively more color noise (cyan in this case) the higher up the sensitivity range. ...