| 摘要 |
A carbon acid-resist, carrying a photosensitive bichromated-gelatine layer, is exposed to light through a gravure screen (8) having transparent lines, through a continuous-tone positive (10) superposed on a tint screen (13) and through the same positive taken in isolation. The order of these three exposures is arbitrary. Finally, the resist (top) is mounted on a gravure cylinder and developed, and the cylinder is etched with acid in the usual manner. The plate obtained has cells, the walls (22) of which are defined by the gravure screen and the bottom (20) is at a general level proportional to the density of the positive, but has, in the medium- and low-density regions of the positive, depressions (17, 21) created by the tint screen. The reproducibility of the tone values is thus improved without having to use two positives, one a continuous-tone one and the other a halftone one. <IMAGE> |
