Color Reproduction
Twenty-plus megapixels of bad color wouldn't be worth much, so it's wise to look at how accurate these cameras perform in a controlled environment. We use Imatest software to evaluate color, with the following standard procedure: We shoot a X-Rite color chart under tungsten lighting, and we feed the files into the application. We shoot at ISO 100, with the camera's neutral and standard settings, capturing both JPEG and RAW files.

After testing scores of cameras, we see enough variation in colors to indicate that it's probably impossible to produce a perfectly accurate camera. We also see enough consistent inaccuracies to indicate that at least some of the errors are intentional. Clearly, manufacturers aim for pleasing, not just simply accurate, color reproductions.

The still life images below were captured in each camera's native RAW format and processed in Adobe Camera RAW (ACR). The top row photos were processed using a neutral ("all off") conversion, while the images below used Adobe Camera RAW's auto conversion. 

Canon 1Ds Mk III	Nikon D3x
1Ds Mk III - Neutral Conversion (ACR)	D3x - Neutral Conversion (ACR)
1Ds Mk III - Auto Conversion (ACR)	D3x - Auto Conversion (ACR)
Canon 1Ds Mk III	Nikon D3x

The X-Rite chart has a six-step grayscale, and 18 patches of color. Imatest generates an interesting chart by plotting each of the X-Rite swatches on an image of a CIE colorspace. The small squares indicate perfectly accurate color and the circles represent the test camera’s color performance. The chart shows both hue and saturation, but not brightness. (If the chart were three-dimensional, the brightness axis would stick out on the axis perpendicular to your computer screen). Color saturation increases with the distance from the origin, so all of the grayscale squares should be dead center. The squares’ distance from the center shows how saturated the colors are, and the direction in which they are offset shows what color they've picked up. The colors follow the same pattern: if a circle is farther from the center than its square, the color is over-saturated. If the circle is clockwise or counter clockwise from its square, then its hue is off.

The Nikon D3X shows more saturation and hue error than the Canon 1Ds Mark III. Though the grays are more neutral, and some greens and blues look marginally better on the D3X chart, Canon does better with most of the hues. Everywhere one camera does well and the other does significantly worse, Canon is the better performer. Interestingly, the 1Ds and the D3X skew the pink and reds toward orange in similar amounts, though Canon bumps up the saturation on those colors more than Nikon. These particular inaccuracies look intentional, since they'll improve most skin tones, many foods, and a range of common subjects.