Wednesday, February 7, 2007
Why does the Foveon X3 outperform conventional sensors?
Since a completed full-color image requires information in all three primary colors for each pixel location, which image sensors using the conventional color filter array doesn't provide the image data mustg be processed using a method called using color interpolation-essentially an educated guess at what the missing colors should be. This guesswork works reasonably well for large areas of color like the sky or an expanse of grass, but it breaks down when areas of different colors get smaller, like the fine stripes on a necktie or the pattern on a multicolored scarf. Due to the inherent limitations of a one-color-per-pixel-location grid there is no perfect solution to the knotty problem of providing the data needed to reproduce fine color details accurately at the edges where colors change. Foveon X3 sensors bypass all these problems by fully measuring all three primary colors using a stack of three color pixels at each pixel location. No interpolation is needed, so there is no guesswork.
Because of their unique structure, there has been some controversy in how to specify the number of pixels in Foveon sensors. While international standards bodies such as the ISO have not yet issued specific guidelines on pixel counting in either multi-chip or multi-channel sensors like the Foveon X3, the pixel numbers presented by Foveon and Sigma are consistent with the present ISO standards and with the CIPA (Camera & Imaging Products Association) guidelines. In any case, the14-megapixel Foveon X3 sensor in the Sigma SD14 outperforms many leading DSLRs in terms of color resolution and overall image quality according to published tests.
Putting it all in perspective
Neither Sigma nor Foveon, the U.S.-based manufacturer of the 14-megapixel X3 sensor used in the new Sigma SD14 DSLR, claims that the Bayer-pattern sensors used in all the leading DSLRs made by other reputable manufacturers are not capable of delivering excellent picture quality. As a result of constant development, careful design and manufacture, and improved software, their performance has been brought up to a very high standard indeed. Nevertheless, we must point out that the overwhelming majority of pictures taken with DSLRs and other digital cameras are shot in color. Optimizing the capture of fine color detail is therefore a crucial design parameter, and here the Foveon X3 14-megapixel sensor provides photographers with a distinct edge in delivering images of surpassing quality. It is perhaps most significant that those who have had the highest praise for Sigma cameras and their Foveon sensors are the testers, professionals, and serious enthusiasts who have actually used them.
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