Understanding Color Gamut: Technologies and Limitations
COR 2: Color Reproduction Systems
Photographic film is one of the best systems available for detecting and reproducing color. Moviegoers are familiar with the difference in color quality between film projections seen in theaters and home video versions. This is because the color gamut of film far exceeds that of television.
Laser Light and Video Displays
Laser light shows use lasers to produce nearly monochromatic light, allowing for colors far more saturated than those produced by other systems. However, mixing hues to produce less saturated colors is difficult. In addition, such systems are complex, expensive, and ill-suited to general video display.
CRT and similar video displays have a roughly triangular color gamut that covers a significant portion of the visible color space. In CRTs, limitations are due to the phosphors in the screen which produce red, green, and blue light. Besides the limitations of the device itself, realistic image display relies on the quality of color sensors, such as those in digital cameras and scanners. Sony has recently introduced a four-color (RGB plus "emerald") color sensor system which may eventually lead to high-end video displays with an even larger color gamut. How practical this is remains to be seen.
LCD and Television Technology
Liquid crystal display (LCD) screens filter the light emitted by a backlight. The gamut of an LCD screen is therefore limited to the emitted spectrum of the backlight. Typical LCD screens use fluorescent bulbs for backlights and have a gamut much smaller than CRT screens. LCD screens with certain LED backlights yield a more comprehensive gamut than CRTs.
Television usually uses a CRT display but does not take full advantage of its color display properties due to the limitations of broadcasting. HDTV is far better, but still somewhat less capable than, for example, computer displays using the same display technology.
Paint and Printing Processes
Paint mixing, both artistic and for commercial applications, achieves a reasonably large color gamut by starting with a larger palette than the red, green, and blue of CRTs or the cyan, magenta, and yellow of printing. Paint may reproduce some highly saturated colors that cannot be reproduced well by CRTs (particularly violet), but overall, the color gamut is smaller.
Printing typically uses the CMYK color space (cyan, magenta, yellow, and black). A very few printing processes do not include black; however, those processes are poor at representing low-saturation, low-intensity colors. Efforts have been made to expand the gamut of the printing process by adding inks of non-primary colors; these are typically orange and green (see Hexachrome) or light cyan and light magenta. Spot color inks of a very specific color are also sometimes used.
Monochrome Displays
A monochrome display's color gamut is a one-dimensional curve in color space.