[ 2006-09-22 11:33 ]
Color television pictures are produced by three different
colors: red, green and blue. These combine to create a whitish light with a
color temperature close to that of daylight (5500 to 6500 Kelvin).
Color temperature is a way of describing the relative amounts of the
different colors that make up the light from a particular source. It can be
thought of roughly as the temperature an object would need to be heated to give
off light with that mixture of wavelengths. At low temperatures, low-energy
colors such as red and yellow predominate; at higher temperatures the
proportions of green or blue increase.
For example, standard tungsten
light bulbs have a color temperature of 3200 K and are very
yellow. Your eyes adjust to this light, making it appear whiter and more like
daylight. At twilight or at night, anything with a higher color temperature than
tungsten lights, such as a television, appears distinctly blue.
The same effect is seen if you look out of a room lit by tungsten light. The
twilight appears particularly blue, and yet if you were to go outside and look
at the same scene, the eye would no longer compare it to the lit room and the
colors would appear more neutral.
The converse is also true. Viewed from outside, the windows of houses lit by
tungsten light sources look distinctly yellow. Fluorescent sources generally
have a spectrum much closer to that
of daylight and don't produce the same effect.
（英语点津 Annabel 编辑）