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Definition: RGB


(1) (Red Green Blue) A prefix tacked on to computer motherboards and peripherals that display colors for a visual effect. See RGB lighting.

(2) (Red Green Blue) The computer's native color space and system for capturing and displaying color images. All TV, computer and electronic display screens create color by generating and combining red, green and blue (RGB) lights. Our eyes are sensitive to red, green and blue, and our brain mixes the colors together (see trichromaticity). See RGBW and RGBY.

Capturing
Cameras and scanners capture color with sensors that record the varying intensities of red, green and blue at each pixel location in the frame. See 24-bit color, CCD sensor, CMOS sensor, scanner and digital camera.

Display Is RGB
For screen display, red, green and blue subpixels (dots) are energized to the appropriate intensity. When all three subpixels are turned on high, white is produced. As intensities are equally lowered, shades of gray are derived. The base color of the screen appears when all subpixels are turned off.

Printing Is CMYK
For printing on paper, the CMYK color space is used, not RGB. Combinations of cyan, magenta, yellow and black ink make up the colors. White is typically the white paper and no ink; however, if white is of critical importance, a white spot color can be added to the CMYK process. See CMYK and spot color.




RGB and CMYK
Display screens have red, green and blue (RGB) pixels. Printers use cyan, magenta, yellow and black inks (CMYK). In theory, equal parts of cyan, magenta and yellow ink make black, but the black tends to be muddy. Thus, black ink is used, making it a four color process (see CMYK).




Video Processing (RGB or YUV)
TV/video signals are generally in the YUV color space. They are converted to RGB in the computer for editing when RGB is the desired output. If YUV is the output and the video editing program supports YUV, there is no need to convert to RGB for internal processing. However, no matter which color space is used for editing, all data must be converted to RGB for the screen. See YUV, Adobe RGB, sRGB, color space and anaglyph 3D.




RGB Color Conversions
Printing requires conversion from RGB to CMYK, and video editing requires conversion to and from RGB and YUV.






RGB/CMYK Comparison
This color picker in Photoshop shows the calibrations of purple in RGB levels from 0 to 255 and percentages of CMYK colors. Also shown are the HSB and CIE Lab color spaces (see HSB and CIE Lab).