
RADIOMETRY AND PHOTOMETRY 401
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λ, Wavelength, nm
xs, ys, zs
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λ, Wavelength, nm
xs, ys, zs
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10
5
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λ, Wavelength, nm
xs, ys, zs
Figure 12.23 Tristimulus computation for three hot objects. The integrands, M
λ
···,
M
λ
¯
x —, M
λ
¯
y −·−,andM
λ
¯
z −− are shown for three different temperatures: 2000 K
(top), 3000 K (center), typical of an ordinary tungsten filament, and 3500 K (bottom) typ-
ical of a tungsten filament in a quartz-halogen lamp. The luminous and radiant exitance,
683 lm/W × Y = 683 lm/W ×
∞
0
M
λ
¯
ydλ,and
∞
0
M
λ
dλ are shown in Figure 12.20, and
the chromaticity coordinates,