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CMOS (Complementary Metal-Oxide Semiconductor) is a technology used in fabricating integrated circuit chips[1]. But in the context of photography, it is one of the two alternative technologies used in digital camera image sensors; the other being CCDs.

Early digital cameras tended to use CCD sensors, as this was the more mature technology. The evolution of CMOS sensors had a steeper learning curve, and originally their use was confined to lower-cost products where image quality was not an overriding concern. However Canon and Sony refined CMOS sensors through several generations; today (2011) when comparing sensors of equal size, CMOS sensors generally exceed CCDs in image quality measures[2].

Typically a CMOS design uses active circuitry placed on directly on the chip itself, which can speed image readout and help with noise reduction. The added circuit complexity does increase the up-front costs to the chip developer; thus we see sensor manufacturer Sony trying to recoup some of those costs by selling sensor chips to its nominal competitors in the camera market: Pentax, Nikon, Leica, etc.

As HD video has increasingly been seen as a must-have bullet point in digital camera sales, the speed advantage of CMOS chips has helped make them the default choice in new camera designs.


  1. CMOS article at Wikipedia
  2. DxO Mark Sensor Rankings at DxO Mark
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