From Imaging Resource...
Now let's compare the Sony A900 to the Canon 1Ds Mark III. I shot both with a Sigma 70mm f/2.8, the lab lenses we use for SLRgear.com testing to get more reliable results. In terms of JPEG shots, the Sony produces larger images that are sharper, especially with the defaults from both cameras, but if you bring both to 100 percent and move around in the images, you'll find they're nearly the same. The difference is in the sharpness, heavily dependent on the default sharpening, and the presence of luminance and red channel noise from the Sony A900, where the Canon 1Ds Mark III does a little better with those artifacts.
Does the superior resolution of the A900 overcome that? Not entirely, but what makes a bigger difference is turning down the A900's sharpening all the way and sharpening later in Photoshop, where you have greater control, something the 1Ds's defaults are already tuned for. Of course, you can also shoot RAW and process those for greater quality from either camera. We've done a more extensive analysis with comparison shots in the Exposure section, and delved deeper into the Sony A900's High ISO noise reduction versus that of the 1Ds under the sub-tab titled High ISO NR. Overall, the 1Ds comes out on top with greater detail, but it's darn close.
What's sure is that the Sony A900 is a fit rival for Canon's best camera, which costs $5,000 more.