Great reductions will, however, be useful when for some special purpose such as the exact reproduction of geometrical figures or surface ornaments are required, as for instance in printing designs for cheques, bank notes, etc. In such cases the drawings should be made as large as is necessary for the most exact and easiest carrying out of the figures, as in this way the precision of the drawing is better kept by reduction. In such cases, assuming that the ornaments are clear and open without shading, the reduction may be carried beyond one-tenth linear.
This kind of reproduction should present no difficulties either to the reproduction or printing.
It is quite different, however, with drawings on scraper boards or grained paper. If it is kept in mind that with too great reduction the gradations of tone of the print will be destroyed, and that in the same degree the difficulties of printing will be increased, care should be taken that reduction is not carried too far. When it is further considered that in a reproduction with 2,000 to 3,000 points to the square centimetre the individual points disappear to the unaided eye, and the different thick layers of points appear as closed tones, the limit of reduction will soon be found.
If we reckon according to this view, we can assume that those kinds of paper with coarse grain should be reduced at the most one-third, those with a finer grain a sixth, at the most a fourth, in order to obtain good printing plates which will give large editions. In this obviously will a good deal depend on the character and more or less rich in detail execution of the drawing. Still there are photo-lithographic processes such as the asphalt process of Orell Füssli & Co., which contains about 15,000 points, and Bartös’ process, which contains 11,000 points to the square centimetre; still for reproduction in large quantities these processes offer many difficulties, and cannot therefore really be taken into account when considering this.
CHAPTER II. THE PHOTOGRAPHIC PROCESS.
1. THE STUDIO.
THE arrangement of the reproduction studio is essentially different to that for ordinary portrait work. The general points of such arrangements are described in detail in the handbooks of Drs. Eder and Vogel, and these I may therefore omit so far as nothing novel is to be observed.
We distinguish now between daylight and artificial light studios; further, those in which a camera is used for making the negative and those in which a dark-room itself is the camera. The first will, of course, be used where other things besides reproductions have to be made; the arrangement without a camera presents many advantages for reproduction work only. In the arrangement with artificial light the illumination of the object to be taken is effected as a rule with a source of light which can approximately replace daylight, and which also remains as constant as possible, and the electric light is at present the best. Although other sources of light are sometimes used, the electric light in the form of the arc light for continuous practical use has the advantage. For copying oil paintings daylight is to be preferred under all conditions, and for this the best arrangement is the revolving studio.[1]
[1] See Eder’s “Jahrbuch für Photographie,” 1893, p. 231.
The description of a modern studio with electric light as used in the K.u.K. Militar-geographischen Institut in Vienna, and from which the studio of the K.K. Hof- und Staatsdruckerei was copied, is given here. This studio lies seven metres below the level of the street on the south front of the building, and is shown in Fig. 2.