The history of three-color photography (1925)

Screen-Plates — Historical and Theoretical Data 459 dyes diffusing from one element to the next. If such happens, there must be either black or secondary colors formed, which if present in any large quantity must influence the color rendering prejudicially. It is, therefore, desirable to reduce the element boundaries to a minimum. It is clear that the lines must be reduced in length, as the size of the elements increases, but they may also be reduced by the use of a particular form without alteration of size. That is to say, as the periphery of a hexagon is less than that of a square of the same area, the total length of the boundaries must be smaller in the regular hexagon mosaic than in a square mosaic, containing the same number of units. Fig. 106 Fig. 107 Fig. 108 Fig. 109 Fig. 110 Fig. Ill If it be assumed that the width of a colored line be 1 mm., Fig. 106, and the area of the plate measure 10x12 mm. ; it will be covered by thirty lines 10 mm. long, and the total length of these lines will be 300 mm. It may also be covered by ten lines at right angles to the others, in which case the total length of the lines is still 300 mm. And if both lines are used, the plate will be divided into a mosaic of 300 units, each 1 mm. square, Fig. 108, and the total division of the lines will be 600 mm. If, however, only one set of lines is crossed, Fig. 107, then the length of this set will be halved, and the total will only be 450 mm. The total length of the dividing lines can, however, be arrived at more easily, by measuring the total length of the several lines bounding one unit, and multiplying by half the total number of units, and this method is applicable to every pattern. Thus, in the line screen, if the lines run the long way of the plate,