Home > Digital Photography > Demosaicing a Raw File

Demosaicing a Raw File

This is how demosaicing works for a RAW file, as I understand it:

  • The image sensor (CCD/CMOS) in the digital camera captures the light information to record an image.
  • Since the sensor only detects light intensity, the color information will have to be separated.
  • On top of the image sensor, over each pixel, is a color filter array (cfa) used to filter the light. Expensive cameras have a 3 separate sensors, one for each color.
  • The most common pattern arrangement (as shown) of the color filters is known as the Bayer filter.
  • RAW files captures the light wavelengths that pass through the filters, and captures a black and white image of all the data. This is known as scene-referred color.
  • The RAW file has to be demosaiced, to pulling all that data together and rendering it as a viewable file in RGB.  This is known as output-referred color.
  • The rendered image can now be manipulated through Camera Raw, Lightroom, or Aperature, or some other PIE software.

Bruce Fraser has written a very easy to understand white paper on Understanding Digital Raw Capture.

Image Source: Wikipedia
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