This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Lighting The Original To Be Copied. Do not arrange the camera and the picture to be copied parallel with the window, but at an angle so that the picture will receive even illumination. This is essential. See Illustration No. 6.
Copying The Picture. As before stated, in order to copy a picture the size of the original, you will need to extend your bellows to twice the focal length of your lens. For instance, if your lens has a 5-inch focus, then extend the bellows to 10 inches. Covering the head and camera with the focusing cloth, slide the camera along from the end of the copying board towards the original until the latter focuses sharp on the ground-glass. When you have the picture focused sharply on the ground-glass you are ready for the exposure.
Stops To Use. When copying good, clear pictures use as large a stop as possible. A good plan is to focus without a stop and gradually stop down the lens until you secure a clear, sharp focus. Then use a one size smaller stop and you will be sure of having a good sharp picture.
Copying Old Pictures. For pictures that are yellow from age, perhaps soiled, etc., you should stop down only enough to make them clear and sharp on the ground-glass, for to sharpen them by stopping to extremes would accentuate the spots and stains. Don't misunderstand-your focus must be sharp, but not wiry, for this class of work. For ordinary work stopping to U. S. 8 or 16 will be sufficient. For some copies, however, especially those you make larger than the original, you must stop down more, using from U. S. 32 to 48 stops, in order to make them clear and sharp, and then time in proportion, calculating your exposure by the appearance of the image on the ground-glass.
Exposing. Having carefully adjusted your plate-holder to your camera and drawn your slide, cover the camera with your focusing cloth, close your shutter and turn the dial to time exposure. Now, the question of time and size of stop to use are very essential. For instance, if the original is a good clear picture, we would advise using a stop U. S. 8 or 16, and, if a bright day, three seconds exposure is sufficient. The exact exposure, however, can only be attained by experience. Three seconds may not be enough; it may require double that exposure. All will depend upon the strength of the light you are working under and the stop used.
514. For your first experiments a good plan would be to make several exposures on a plate, as follows Draw the slide part way, exposing part of the plate, and give three seconds exposure; draw it a little further and give another three seconds exposure; finally, draw the slide entirely and expose again. You will now have three different exposures on this plate, the first portion having received 9 seconds, the second 6 seconds, and the third 3 seconds. Proceed to develop the plate. Some one of these exposures should be correct, and will serve as a guide for future exposures. After a few experiments you will be able to judge quite accurately the correct exposure for all classes of copies.
Developing. Normal developer should be used, and all copies having a full exposure must be treated as such in the development. Copies must be developed farther than other exposures, and, to avoid fog and retain snap throughout the development, add three to five drops of a 10% Bromide solution to your normal developer. Mix well and proceed to develop. Copies should be carried one shade farther in the developer than regular exposures.
Printing. The quality of the original from which the copy is to be made should determine the printing paper to use. If the original was a good clear print, any printing paper may be used. If the original was flat, then developing paper should be employed, as more contrast can be obtained. Platinum paper usually gives the most satisfaction, as the imperfections, grain of the paper, etc., of the original will show less on this paper.