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Figures (7)

Fig. 1
Fig. 1

Shapes of openings in templates used in making positive color-separation transparencies for Life spectrum.

Fig. 2
Fig. 2

Shape of opening in template used in making calibration stepped-density transparency for surveying colors obtainable with Life color printing process. Above: Densities of steps produced by corresponding apertures of template. Broken curve permits interpolation of aperture sizes necessary to produce intermediate densities.

Fig. 3
Fig. 3

Chromaticities obtained by superimposed proofs of pairs of Life printing inks are shown at intersections of curves in standard I.C.I. chromaticity diagram. Curves are designated by letters corresponding to those assigned in Fig. 2 to steps of calibration transparency.

Fig. 4
Fig. 4

Errors of dominant wave-length of a good copy of Life spectrum, shown as a function of nominal wave-length (according to printed scale). Below: Errors of dominant wave-length evaluated as multiples of just noticeable differences.

Fig. 5
Fig. 5

Tone distortion curves of components of Life spectrum. Ordinate shows density of the step of the calibration transparency from which was obtained the same color as that printed in Life spectrum (at a wave-length for which the printer’s copy had the density indicated by the abscissa). The straight line at 45° shows expected tone reproduction, which would have been obtained if the spectrum printing plates had been made exactly the same as the original calibration engravings. The curve which crosses the ideal line represents the distortions of all three printed colors between 536 mμ and 605 mμ. The upper curve shows characteristics of insufficiently etched portion of the yellow printing plate between 605 mμ and 700 mμ. These distortions are responsible for the orange appearance of long wave-length end of Life spectrum. The lowest curve shows characteristics of excessively etched portion of magenta printing plate between 400 mμ. and 535 mμ.

Fig. 6
Fig. 6

Construction of patterns of superimposed pieces of 0.1 density neutral filter-film used in preparing Plate I. The shapes of the pieces were derived from Fig. 3, corresponding to the densities produced by photographing a trial assembly of 0.1 density neutral filter-films. Note the sectional view of the pile of filter-films shown at upper left. The coordinates shown for each pattern correspond to those in Fig. 3. Broken lines indicate the shapes of opaque masks which surrounded each pattern and concealed irregular ends of pieces of filter-film. These patterns were placed on an opal glass illuminated uniformly from the opposite side, and were photographed full size with a simple aperture (pinhole, no lens) having diameter equal to half the width of the widest step in the patterns. The engraved printing plates made from the resulting smoothly graded transparencies were trimmed corresponding to the dotted boundaries shown in the patterns.

Plate I
Plate I

Distribution of colors in I.C.I. chromaticity diagram, showing gamut obtainable with a modern commercial process of color printing. The colors are approximately correctly distributed in the diagram when the plate is illuminated with daylight. (Inserts provided by Life, reprinted from issue of July 3, 1944.)