Color Management of Four-Primary Digital Light Processing Projectors

Traditionally, hardware for additive color displays, including projection devices, has been built from a set of only three primaries: a red, a green, and a blue. Recently, some manufacturers of projector displays have designed their hardware to project a fourth primary, a white. This fourth primary has been helpful in increasing the luminous output possible from these displays. Because interdevice color communication infrastructure is based on red, green, and blue channels (RGB), the four-primary devices accept RGB digits and internally convert to red, green, blue, and white channels (RGBW). From a color management viewpoint, the four-color projectors look like RGB devices, but the typical color characterization models fail owing to the complexity introduced by the hidden RGB to RGBW conversion. Several four-primary digital light processing projectors were investigated and a new characterization model is proposed that approximately accounts for the relationship between RGB digital counts and resultant projected colorimetry.