The use of video cameras based on charge-coupled devices (CCD's) for color measurement is a new and
growing field which does not fit into any established category of image processing.
Just as silicon photodiodes replaced photomultiplier tubes in colorimeters twenty years ago, the CCD
array is beginning to replace the silicon diode today. A good colorimeter has a measurement repeatability
of the order of 1 part in 10,000, or 0.01 in XYZ or L*a*b*. By contrast, most video frame grabbers are
limited to a resolution of 1 part in 256. However, because a color camera can produce in excess of 23
million 8-bit numbers per second, appropriate image processing may be used to improve repeatability and
In this paper, the CCD camera is evaluated from the standpoint of conventional colorimetry. The
following points are addressed: requirements of a camera to be used for color measurement; possible
physical configurations; sources of noise and repeatability of color measurements; image processing
algorithms for colorimetry; RGB-to-XYZ transformation; and requirements for an image processor to be
used with a camera-based colorimeter.