
RADIOMETRY AND PHOTOMETRY 381
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0
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Wavelength, nm
y
Figure 12.9 Photometric conversion. The
¯
y curve shows the response of the standard
human observer. The dotted line shows the data, and the solid line shows the fit provided
by Equation 12.42.
Suppose that a scene includes four light-emitting diodes (LEDs), blue, green, red, and
near infrared, all with equal radiance. We will see in Equation 13.4 and Figure 13.2 that a
silicon CCD will usually be more sensitive to longer wavelengths, making an image from a
monochrome camera (single-channel black and white) more likely to show the infrared diode
to be the brightest and