There's one compact camera that has caught the imagination of photographers over the last couple of years. It's rare for a compact to stir up much anticipation, but the Sigma DP1 has done just that. It's been a long time coming, being first announced at Photokina 2006 as a development model. The main reason for the fuss is its sensor: the controversial Foveon X3 sensor capable of 14MP resolution, and the first APS-C sized sensor in a compact digicam.
The sensor, last seen in the Sigma SD14 DSLR, has aroused criticism due to the way the image is captured by three layers of photocells buried within differing depths of the silicon substrate. One of silicon's properties is the way it absorbs red, green and blue light at different depths and Foveon uses that property to build the pixels within three strata of the chip. Traditional CCD or CMOS sensors have the photocells on top of the chip, and use a Bayer RGB filter to separate the different colours. This has led critics of the Foveon chip to claim it's a lower resolution sensor of 4.7M as that is the final image size you end up with. On one side of the argument, the sensor does have 14MP (4.7MP over each three layers) but the flip side of the argument is that the final image is only made up of 4.7MP in total of those images. I'll leave the argument to be fought out in the forums, but in terms of image quality and so forth the image produced is 4.7MP, and that's what we'll take as our starting point for assessment.
Sigma has developed a new processor, the Three-layer Responsive Ultimate Engine or TRUE, which is designed specifically to deal with the files from the sensor and also handle JPEG conversion, a feature lacking on the early Sigma DSLR range which were RAW-only until last year's SD14.
The other major feature of the DP1 is the lens, a fixed focal length 16.6mm f/4, giving a 35mm equivalent focal length of 28mm. I think this a little wide for day-to-day shooting, and would prefer a 35mm equivalent, but I'm sure there are plenty of people who would disagree. Sigma also has an optional lens hood, which is recommended, not just to reduce flare, but for the aesthetic quality it lends to the camera, providing a traditional rangefinder look.