CONTROL IN PRINTING Methods of treating negatives, or methods of treatment adopted while printing, may be summarised under the above heading. The object in all cases is the same ; namely, to pro duce a better, a more harmonious, or a more satisfactory print than that which the negative would give if the ordinary course were pursued. It is quite incorrect to assume that it is only inferior or imperfect negatives that require such assistance. The more critical the worker becomes with regard to his results, the more will he adopt methods of control. In a large proportion of subjects, the lighting or other conditions may render the resultant negative inharmonious—not necessarily harsh or imper fect technically, but inharmonious in the sense of there being strong lights, or emphasis, in parts where such strength is detrimental to the general effect. It is control for securing true balance of light and shade, and for obtaining the most artistic result, that is the object of the treatment described.
The most simple method of control consists in shielding those parts of a negative which tend to become too dark, while the remainder of the print attains its full strength. In some cases this may be a simple shielding of a small corner or one end, while in others it may be necessary to shield almost the entire plate while a small part prints out fully. In printing by diffused daylight, a piece of thin wood or card may be supported at about in. or r in. above the sur face of the negative, and covering those parts that attain their full depth too soon. The light diffuses gradually under the edge of the shield, grading softly from full action through the un shielded portions to practically no action at all under the greater part of the shield. The manner in which the change is effected, the sudden or the gradual transition from full printing to no action at all, will be determined by the distance of the shield from the negative. Even if as close as f in., no line or sudden mark will show. In the case of a bright window in an interior photograph, a hole may be cut in a sheet of card, and the card supported above the negative so that the hole is exactly over the window, allow ing its details to print out fully while the other parts are restrained. The effects of slight hala tion may be entirely removed in this manner without any work on the negative.
In printing by artificial light, the same results may be obtained bylkeeping the shields in motion while they are in use. By that movement, the risk of a sharp line showing is entirely obviated.
The greater the extent of the movement of the shield, the softer the transition of its effect.
A second method, which is very useful in those cases in which there is a well-marked line in the subject at which the change in strength of printing should be made, consists in covering the glass side of the negative with very thin tracing paper or ground-glass varnish. The paper or varnish is cut away from those parts that print too slowly. The tracing paper to employ is that sold by artists' colourmen under the name of papier vegetal, or vegetable tracing paper. It is very thin and translucent. It should be slightly damped and attached to the glass at the margins by a little gum. When dry, parts may be cut away as desired, the edges of the cut parts being secured by a touch of gum. Matt varnish is finer in character, but more difficult to apply. The degree of restraint pos sible may be increased by using a yellow-tinted varnish. The extent to which parts of a negative are held back in printing by this method is not great, but still sufficient for all ordinary nega tives. A negative that has been prepared in this manner can be printed quite successfully by artificial light by the simple expedient of Keeping the frame moving slightly during the exposure. In diffused daylight, no movement of the frame is necessary, the thickness of the glass plate being sufficient to diffuse the light and prevent hard lines showing at the edges.
A third method of controlling results consists in cutting out a mask that will fit exactly those parts which require holding back. The most satisfactory way of making the mask is to take a silver print from the negative, and, having cut out the parts that print too quickly, to fix them to a piece of plain glass the same size as the negative. They should be put on in such a manner that when the glass is laid exactly over the negative the cut pieces will be in the pre cise position necessary. The printing is com menced in the usual manner, and as soon as the parts that correspond with the mask are sufficiently dark, the glass that bears the cut-out pieces is placed in position, care being taken that the corners coincide with the corners of the nega tive, thus ensuring that the mask is exactly in position. Although it involves more trouble in printing than does the use of tracing paper or matt varnish, this method possesses the advantage of allowing any degree of restraint to be exercised.