it were exposed at a distance of two feet above the targets at
the time of each pass. While the effects of atmospheric absorp
tion and scattering on the light impinging on the targets are
included in the normalized relative target reflectance, the
absorption and scattering of the target’s reflected light and
the contribution of general scattering viewed by the camera dur
ing flight is not included.
BASES OF COLOR DETERMINATIONS
The spectral transmittance of the transparencies was measured on
a Leitz MPV microspectrophotometer equipped with an in-line
monochrometer. A 0.12 mm monochrometer fixed slit opening was
used resulting in the passage of 50 percent of the peak trans
mission in a passband of 1.2 to 7.8 nanometers when used over the
wavelength range of 380 to 720 nanometers measured in this study.
The Xenon light source and the type F Photovolt detector allowed
precise measurements over the measured wavelength range.
Multiple transmittance measurements were taken at each 10 nanom
eter interval from 380 to 720 nanometers with a digital voltmeter
using the average of four readings per interval to reduce the
noise level. A total of twelve sample spots were selected at
random within each target. A detector aperture size of 40 mi
crons square was used for all measurements. Other equipment
included a paper tape punch and a paper tape to magnetic tape
interface system. The color analysis was performed on an
IBM 370/165 (Hansen, 1973).
The 1960 CIE-UCS u,v chromâticity scale was chosen for color
description as equal displacements on the UCS diagram corre
spond to perceptually equal color differences (Wyszecke and
Stiles, 1967). This scale is a linear transformation on the
1931 CIE x,y chromaticity diagram and is given by the following
formulas :
-2x + I2y + 3
V = -2x + lly + 3
In addition to describing the chromaticness in terms of the u,v
coordinates of the UCS diagram, lightness is expressed in terms
of the visual transmittance given by the Y tristimulus value:
720
= 2 E„ IT (at 10 nm intervals)
380 C Y X X
Y
