6.3 Color Gamut Improvements

The color gamut shown in Fig. 5.2 in Chapter 5 limits the number of reproducible colors to the triangle derived from the three primary colors. As explained in Sec. 6.1.1. in this chapter, more saturated colors can be obtained with denser color filters, at the expense of luminance. A more attractive approach is to use a backlight with narrower peaks matching color filters with equally narrow width. For example, a well-designed LCD with an RGB LED backlight can have a better color gamut (close to 100% NTSC).

Another method to increase color gamut is the use of more than three primaries. LCDs with four and six primary colors have been demonstrated, by employing additional subpixels with different color filters. This approach requires extra processing and conversion of RGB data signals to multiple color signals in image processing. An example of the resulting improvement possible in the color gamut is schematically shown in Fig. 6.12 for a display with six primary colors. The addition of more color subpixels, which each transmit a smaller fraction of the backlight intensity, is likely to reduce luminance. Whether this color improvement is practical in terms of cost therefore depends on the application.

Figure 6.12: Increase in the color gamut by using more than three primary colors.