Appendix B
StillColor
©
National Instruments Corporation
B-7
PCI/PXI-1408 and NI-IMAQ for Win95/NT
Introduction to Color
Color is the wavelength of the light we receive in our eye when we look
at an object. In theory, the color spectrum is infinite. Humans, however,
can see only a small portion of this spectrum—the portion that goes
from the red edge of infrared light (the longest wavelength) to the blue
edge of ultraviolet light (the shortest wavelength). This continuous
spectrum is called the visible spectrum, as shown in Figure B-3.
Figure B-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.