X3

A full-color image sensor for still and video cameras from Foveon, Inc., Santa Clara, CA (www.foveon.com). Introduced in 2002, the CMOS-based X3 chip is more analogous to film than the CCD and CMOS chips in common use because it stores all three colors (red, green and blue) in each pixel. In addition, traditional sensors capture only one third of the color per pixel, using a checkerboard-like mosaic of red, green and blue pixels that have to be interpolated by complex processing. The interpolation often causes unwanted effects such as "purple fringing," which is a line of color outlining dark areas such as brown or black hair. See Bayer pattern and purple fringing.

X3 Vs. Mosaic

X3 stores all three colors per pixel compared to the mosaic approach where only one third of the color is stored per pixel. The mosaic method requires elaborate processing to interpolate the missing colors. Taking the pixel at the upper left corner of the checkerboard as an example, the computer has to figure out how much red and blue there really might have been at that pixel, because the filter only let it sense the intensity of green.