Many artists favour crayon work on a grained paper, adopting a broad sketchy treatment in liberal proportions, so that in the subsequent reduction the freedom of the original will be toned down just sufficiently to enhance the picturesque and artistic value. Drawings made on scraper boards, grained papers, or by the aid of shading mediums, are photographed and reproduced by the ordinary line method. In making sketches for “half-tone” photo-mechanical reproduction it must be remembered that, as far as photo-lithography is concerned, it is impossible to accentuate effects by what is known as “fine etching” when applied to photo-engraving. A negative for photo-process work of any description should be absolutely perfect in every respect. The whites of the copy in the negative should be of an absolutely opaque black, showing clean, sharp edges, with clear glass representing the lines, dots, etc. These are all-important factors, and their influence upon the reproduction of the original can scarcely be over-estimated.
CHAPTER XVII
Photo-Lithography—continued
A Copying Table—Exposure—Illumination—Photo-litho Transfers—The Paper—Printing—Developing—A Direct Process.
To discuss the respective merits of the “wet” collodion, collodion emulsion, and dry-plate processes lies beyond the province of this work, as does also a detailed description of the operations involved.
The processes are purely photographic, and have already been presented to the craft in various forms. It is, moreover, almost impossible to bring within the limits of a single chapter anything approaching to a comprehensive record of the multitudinous details upon which process photography is based. All that can be attempted is to take one or two outstanding features which suggest a few useful hints.
The original or copy for reproduction must be on the same optical plane as the sensitive plate in the camera, i.e. they must be absolutely parallel with each other. There are several ways of ensuring this. The most convenient method is to use a copying table and board similar to [Fig. 31]. With such an arrangement as this direct copying can be attained through the lens, or the camera can be turned half-way round, and the image reversed by means of a mirror or prism attachment. The chief advantage of such an arrangement is, that the position of the camera can be altered at will without affecting the relative positions of the plate and copy.