Appendix A
StillColor
©
National Instruments Corporation
A-7
Figure A-3.
White Light and the Visible Spectrum
White light is a combination of all colors at once. The spectrum of white
light is continuous and goes from ultraviolet to infrared in a smooth
transition. You can represent a good approximation of white light by
selecting a few reference colors and weighting them appropriately. The
most common way to represent white light is to use three reference
components, such as red, green, and blue (R, G, and B primaries). You can
simulate most colors of the visible spectrum using these primaries. For
example, video projectors use red, green, and blue light generators, and an
RGB camera uses red, green, and blue sensors.
The perception of a color depends on many factors, such as:
•
Hue, which is the perceived dominant color. Hue depends directly on
the wavelength of a color.
•
Saturation, which is dependent on the amount of white light present in
a color. Pastels typically have a low saturation while very rich colors
have a high saturation. For example, pink typically has a red hue but
has a low saturation.
•
Luminance, which is the brightness information in the video picture.
The luminance signal amplitude varies in proportion to the brightness
of the video signal and corresponds exactly to the monochrome
picture.
•
Intensity, which is the brightness of a color and which is usually
expressed as light or dark. For example, orange and brown may have
the same hue and saturation; however, orange has a greater intensity
than brown.
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