Compared to...

Studio scene comparison (RAW)

This is our standard studio scene comparison shot taken from exactly the same tripod position. Lighting: daylight simulation, >98% CRI. Crops are 100%. Ambient temperature was approximately 22°C (~72°F).

Sigma DP1 (upscaled image) vs. Canon EOS 450D

Camera settings:

• Sigma DP1: Aperture Priority, ISO 100, RAW, Manual WB
  Default Parameters, Self-Timer
  
  
• Canon EOS 450D: Canon EF 50 mm F1.4 lens, Aperture Priority, ISO 100, RAW,
  Manual WB, Default Parameters (Standard PS), Self-Timer (+MLU)

For the purpose of this comparison we have upscaled the Sigma DP1's output to (approximately) match the image size of the Canon EOS 450D. We therefore chose the the 'Large (large prints) 13.9 MP' option when saving the DP1 RAW image as a JPEG in the Sigma Photo Pro software.

Sigma DP1 RAW	Canon EOS 450D RAW
3,088 KB JPEG (4573 x 3048)	3,747 KB JPEG (4727 x 2848)

While the DP1 delivers a large amount of detail at its native resolution of 4.6 MP the upscaled RAW output cannot keep up with the 450D. The Canon is sharper and shows more detail. There are also some sharpening artifacts in the Sigma image. It appears the Photo Pro software applies sharpening to the JPEG output before it upscales the image and therefore 'amplifies' the artifacts.

What you're seeing here is the essential limiation of the X3 system as it currently stands; the per pixel sharpness is peerless, but the low spatial resolution means that compared to the latest generation of bayer sensors - even in entry level models - there's only so far you can take it.

That said, it's worth noting that the DP1 is actually getting very close, even upscaled this far, to matching the Canon EOS 450D and would give lesser DLSR models a real run for their money (especially if you put a little effort into optimizing the raw output). Unless you produce big enlargements there's plenty of detail in the Sigma's files.