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.
Plate Develops Thin. A plate that develops thin and cannot be carried further in the developer is an extremely underexposed plate, while if thin and the shadows are filled with detail it is extremely over-exposed but under-developed. In either case treat your plate according to the exposure, when developing, and always carry copy-negatives a little farther in the developing than you would other exposures.
Determining What Plate To Use. If you follow the instructions carefully and observe the results you obtain, after a few experiments you will be able to readily determine what plate you should use. For colored pictures you are told to use Isochro-matic or Orthochromatic plates. As a rule, for black and white subjects and engravings it is advisable to use ordinary slow plates.
Determining What Size Stops To Use. Never use a stop smaller than is absolutely necessary to produce a sharp image. For copying drawings, engravings, etc., in which extremely fine lines are to be reproduced, it is advisable to use a small stop as this will prevent the clogging of these very fine lines. You will find that when you desire to produce contrast it is always advisable to use a small stop.
Knowing What Lens To Use. If you are fortunate enough to own a number of different lenses, the selection of the right one might be a difficulty. A single lens is not to be recommended unless you are making a copy much smaller than the size of the plate it is made to cover and, even then, you will find it will be necessary to use a small stop. An ordinary Rapid Rectilinear Lens will be found to fill the requirements, but it must be used in a good light to make up for the loss of illumination when it is stopped down sufficiently to cover the extreme corners of the plate. When, however, a color filter has to be used in a dark or poorly lighted room this type of lens is almost worthless. The very best lens for copying is one of the anastigmat type because of its exceedingly flat field and its freedom from distortion when used at full aperture on the size of plate it is listed to cover.
Obtaining An Image The Size Of The Original. When a small and short focus camera is used there is no attachment that will give you such good service as the Ideal Copying Lens, which slips over the regular lens and shortens the focus at least one half. By means of this lens any hand or view camera can be used for copying and an image the same size or larger than the original can be made, providing the original is not larger than the size plate your camera will hold.