Electronic computer for color printing

PROBLEMS of color deficiency have been associated with color photography and magazine printing for many years and, more recently, with color television. The development of the additive and subtractive color theories in which the reproducing primaries are related to the spectral sensitivites of the 3-color-separation photographs, has been described by Hardy and Wurzburg, Jr.1 A basic relation between the additive and subtractive contributions of the common printing process for a 3-color process was published in the same year.2 The equations derived relate the transmissions of the 3-color-separation photographs to a function of the amounts of the inks and their tristimulus values. With the daily production of millions of magazine issues in the United States using a fourth (black) ink, compared to the smaller editions in Europe for which these equations apply, a modification to the equations was necessary to include the effect of the black ink used in the high-speed printing methods in this country. These final equations for color correction were published in 1948.3 Where V is the vector of the red (R), green (G), and blue (B) tristimulus values of a color and the subscripts of V are the tristimulus values for the paper, full inks and full over prints of inks, the equation for the percentage of cyan (c), magenta (m) and yellow (y) inks is