The Sigma DP3, as compared to the DP1.
The larger size is necessitated by the addition of several features, including a full frame sensor. I don't know if I got the size comparison exactly right, but it wouldn't have to be too big. The Leica M9 has a full frame sensor, and it's only 5.5" x 3.1" x 1.5".
The Sigma DP3 Feature List
- A full frame, 24 megapixel Foveon X3 sensor producing a final image size of 8 megapixels.
- Interchangeable lenses.
- 1080p video. (With an appropriate variety of frame rates, including 24 and 29.97, and autofocus, and manual exposure controls. And a microphone input jack.)
- Sensor-shift image stabilization.
- Weather sealed body and lenses (for shooting in rain/dust storms).
- Reasonably fast performance (meaning startup time, focusing time, shutter lag, shot to shot time, etc.).
- A built in electronic viewfinder with sufficient resolution to allow it to be used for focusing.
- A flip-out, articulated AMOLED screen.
- Decent continuous shooting mode with a reasonable buffer size.
- Raw+JPEG shooting (yes, it's true, the DP1 actually does not have this).
- An autofocus assist lamp. Seriously, we all need one sometimes.
- A nice assortment of lenses to go with it, including some fast, sharp primes.
- And of course all the niceties already included in the DP1 such as great build quality, full manual control, customizable controls, hot shoe, good high ISO performance, stunning image quality etc., etc.
P.S. In case it's not abundantly clear, this is not a real camera. It's an example of what a camera that I would get excited about might look like. The image above is a composite of the Sigma DP1 and the Panasonic GF1 made using images stolen from Digital Photography Review.