Tone Reproduction Cycle
LBR B/W Positive = Color Positive Transparency = Color Paper Product
Ill. Positive Color Paper
Reproduction
Y
Density a Digital Value
T
T T T T T T T T T T T T
0 3 6 9 1.2 1.5 1.8 2.1 0 17 35 51 69 85 103 119 137 153 171 187 205 221 239 255
Il. Color Positive Transparency 1s] |. Laser Beam Recorder Output Specification
Reproduction :
= — Linear LBR Output pan
Precorrection for :
Photographic Reproduction
Figure 2.--Density curve transformation of Landsat digital brightness
values to final photographic color proof that approximates the
color rendition desired in the lithographic product.
Quarter-tones at 25 and 75 percent vary with the images, but in general
they are assigned closer to endpoints than to the midpoint to improve
contrast in the highlight and shadow areas. The cyan separation is evalu-
ated first as it carries the shape and contrast of the features in the
imagery. If the cyan halftone black-and-white film separation looks good
as viewed on white paper (not back-lighted), the final printed map is
likely to look good. Yellow and magenta separations generally follow the
cyan tone curve with a lO-percent drop at the midtone and 5-percent drop
in quarter tones. Reductions in the yellow and magenta tone curves are
made to correct for lithographic ink deficiencies. If the ink pigments
were pure, equal densities of ink in each of the separations would combine
to make tints of gray (fig. 3, Kidwell and McSweeney, 1985).
Adjoining map sheets will be generally visually acceptable if the
adjoining density values for the cyan separation can be made to fit
between the quarter-tone and midtone and the midtone to three-quarter
tone. Endpoints for highlight and shadow will be forced to match in
reproduction by the offset printing halftone process.
Electronic interactive color displays and photographic color dyes in the
blue, green, and red additive color gamut contain a wider range of colors
than are possible using ink pigments of the subtractive colors of yellow
210
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