sources are listed in figure 1-10. To the eye, most of these light sources
appear the same but they will not photograph the same with color films.
Figure 1-10.
Approximate color temperature of commonly used
(1) These experiments involved observing the color changes in a
"black body" when heated to a high temperature. A black body is a perfect
temperature radiator.
It absorbs all the heat incident upon it and
reradiates it immediately.
A true black body does not exist; therefore,
actual
Kelvin
values
are
based
on
scientific
experimentation
and
mathematical calculations.
(2) When the black body was heated and a color change occurred, the
temperature was noted and, thereafter, used to identify that particular
color.
Lord Kelvin used "absolute" temperatures (Kelvin temperatures) in
his measurements.
Kelvin temperature is written as K and is centigrade
temperature of the black body plus 273 degrees.
Lord Kelvin used his
process to establish values for the special characteristics of light.
1-17
SS0514
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