Spectral response of typical lead-oxide and
vidicon pickup tubes compared to the human eye
c. The response of the eye peaks near the wavelength of yellowish-
green. This indicates that a given amount of light energy may appear much
brighter at some wavelengths than at others. The curves also show that the
response of the various types of pickup tubes do not match.
The other two variables of color, hue and saturation, are controlled
by the relative spectral distribution of light energy. Hue is determined by
radiant purity, or freedom from white light.
a. Figure 2-4 shows a spectral radiation energy curve spread out more
or less uniformly over the visible spectrum. When such a condition exists,
white is seen as a pale or pastel shade.