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DPReview | New Sigma SD1 with Foveon X3 4800x3200 Full-Color Sensor

Sigma SD1DPReview.com has excerpts from an interview where Foveon and Sigma leads discuss the new 15MP x 3 sensor that was announced at Photikina 2010. This new sensor will be featured in the forthcoming Sigma SD1 that Sigma plans to release in the spring of 2011. The new sensor is 4800 x 3200 pixels times 3, one layer for each of the three RGB color channels.

All other camera sensors only capture a single color channel at each pixel location by applying a Bayer filter over the sensor. To get a full RGB triplet, they have to interpolate the two missing color channel values for each pixel by using the values from their neighboring pixels of different color channels. This is called demosaicing. This interpolation produces jagged edges and other artifacts. In order to compensate for this, these sensors then have to perform anti-aliasing which ends up softening the image. We then have to sharpen these images during post processing to bring back the crisp edges that provide that apparent level of detail. This is a point where noise in the image can be exaggerated, particularly in music photography where we shoot under low light with lots of dark areas in the background.

Foveon sensors employ an architecture of three layers of sensors (like film layers). This permits the Foveon sensor to capture all three RGB color channel values at every pixel location. In turn, Foveon sensors produce sharper, more color accurate images that have smoother transitions and more detail because they do not have to perform the same demosaicing and anti-aliasing that softens the image, and we do not have to apply the same level of sharpening that exaggerates noise.

There are sensors that produce "sharper" images with more detail. However, this is more of a factor of the number of megapixels they capture than the design of the sensor (like the 24MP Nikon D3x or the 21MP Canon 5D Mark II).

The Foveon X3 technology has a lot of potential. With this latest sensor, Sigma and Foveon will be right in the middle of the competition in the megapixel race with the other major camera makers. This is great news. Whether you consider testing and switching to the Sigma technology, or you wait for your own camera maker to develop similar full color technology, this announcement should up the game on the quality of digital imagery coming from all camera makers.


Click here for a good illustration of the difference between Bayer sensors and the Foveon layered sensor architecture.