HINTS ON COP YING.
To copy a photograph or _ _ engraving with the ordinary camera, the picture should be hung or clamped to an upright frame, where its surface can be made perfectly flat and smooth. The picture should be so hung that it may receive a strong light, not sunlight. If you have a win dow facing the north, the picture should be near the window and partly facing it; then the camera should be placed directly and squarely in front of the picture, the lens being of the same height as the center of the picture. Care must be taken to have the camera directly in front of the picture, so that the picture will be exactly parallel, to the ground-glass; then there will be no danger of any distortion in the negative. This is of the utmost import ance. No true copy of a picture can be made unless the plate or ground-glass and picture are parallel, A slow plate is the best to use for copies. In copying on cloudy days in the fall or winter, we prefer very quick plates. The camera is placed near, or at some distance, from the picture, as the copy desired is to be large or small. In making a copy for a lantern slide it must, however, be remembered that the picture is to be copied across the small plate, and not the long way of the plate, in the same way that pictures are always printed upon lantern slides. The ground-glass should be marked in pencil so that it will show the location of all smaller size plates; that is, if your camera is a 5x8 size, you should lay out on the ground-glass the position of the f size and 4x5, and also of the 4.ix6i, which is the half-size plate, if you expect to use them. Then, when, as in the present case, you wish to make a copy on a quarter size plate, the picture, when in focus on the ground-glass, will show whether the camera should be moved nearer to, or be set further back, in order to get the copy of the desired size. In copying it is essential that the focus should be as exact as possible, and, to aid in getting a fine focus, it is a good plan to lay a piece of printed paper against the pic ture and focus with the magnifying glass on the letters, remember ing to remove the paper before making the exposure. When the
focusing is done, a small stop should be inserted in the lens, and the cap put on so that it can be removed easily, which must be done without jarring the camera in any way. The time of expos ure will vary according to the subject to be copied. We may say that, using an f32 stop, the time will vary from 50 seconds to 5 minutes. An ordinary engraving or photograph that has a dark, strong tint, will require less exposure than a picture printed light or altogether in, half tone.
Highly burnished photographs, especially such as are not flat, are difficult subjects to copy. The light must be so arranged that no part of the glazed surface will reflect any band of light into the camera.
To photograph white statuary requires long exposure, and screens properly adjusted to light up the subject. A white screen should be used over the window to diffuse the light. If circumstances admit, altogether the best arrangement is to photograph statuary out of doors, in the shade, with a black screen for a background. In developing, use more than the usual quantity of No. 1, to secure great intensity.
An engraving in outline, simply black lines, will require long exposure, perhaps three times the exposure of an ordinary photo graph. A copy of a printed page or of a letter in black ink will need long exposure, and also long and intense development. Copies of paintings should be made always with orthochroraatic plates, and the painting should be so hung for copying that there is no bright light reflected from it into the camera. The light illuminating the painting must come from directly in front, to avoid little shadows that might be caused by oblique light falling on thick patc.hes of paint. If any doubt exists as to the proper exposure to be given, it is safer to lean to the longer time. It has fre quently been our experience in copying engravings that the dif ference of one or two minutes in the exposure made no differ ence in the quality of the negatives, provided only that time enough was given.