Does a Color Television Work by Color Addition or by Color Subtraction?

Light and Color

• Visible light makes up part of what is known as the electromagnetic spectrum. Depending on the wavelength of the light, we perceive it as a particular color. The colors in the visible spectrum is typically defined as red, orange, yellow, green, blue, indigo and violet. White light contains all the different wavelengths all at once. An absence of color is perceived as black.

Primary Colors

• In traditional color theory, the primary colors are red, blue and yellow, and you mix these to make different colors. This can create some confusion, because you need different sets of primary colors to produce your desired shade in different contexts. The primary colors in printing, however, are magenta, cyan and yellow. In the world of TV technology, the three primary colors are red, blue and green.

Color Subtraction and Color Addition

• When you perceive something as having a certain color, what you are actually seeing is the light that's reflected back to you from the surface. You perceive a red object under white light as red because it reflects red light wavelengths while absorbing other wavelengths. This is color subtraction. In color addition, you add light of different wavelengths together. Your eyes interpret the result as a new color.

Pixels and Subpixels

• A television screen is covered in thousands of tiny dots called subpixels. These are grouped in threes, one blue, one red and one green, to make a pixel. Because the subpixels are small and densely spaced, your eye can't distinguish them at a normal distance and sees each group as a uniform dot of light. You can confirm this by examining your television screen with a magnifying glass.

Color Mixing

• When all the subpixels in an area of the screen are turned on, you perceive the light as white. If only one subpixel in each group is lit, you'll see the color of that subpixel. For example, if only the blue subpixels are lit, that part of the screen will appear blue. A blue and a green subpixel make cyan; red and blue make magenta; red and green make yellow. Different proportions of each color create different shades. When all the subpixels in one area are turned off, you perceive that area as black. In actuality it is the same color as your screen when it's switched off -- usually a dark gray.