Sigma SD1 - Ready For Prime Time

The Foveon X3 Sensor
First announced at Photokina in September, 2010, theSigma SD1has finally become a reality. Scheduled to ship in early June at a MSLP ofUS $9,700 the SD1 is Sigma's new flagship model and features the largest and highest resolution Foveon sensor yet. It has an APS-C sized (1.5X crop factor over Full Frame 35mm) sensor with a spatial resolution of 15.3 Megapixels. Due to its Foveon X3 sensor design it has a colour resolution of 46 Megapixels. 
Because this is the most controversial and confusing aspect of Sigma / Foveon sensor-based cameras it's important to spend a paragraph or two discussing this right off the bat.
Other than sensors that useFoveon X3 technologyall sensor (CCD and CMOS) use what is called aBayer Matrix so as to be able to reproduce colour. Silicon photo sites are not able to record colour directly, and so variousFilter Arraytechnogies have been developed to make this possible. A Bayer matrix is by far the most common, and is used i...