For instance, to bring out the gradation of the sky in a landscape negative, a piece of card. is used, cut either with a straight edge or accord ing to the outline pencilled on it (before the sensitive paper has been placed on the easel) while it is held about half-way between the lens and the sensitive paper. This card is moved, during part of the exposure, to and fro or up and down.
To lighten the face of a model dressed in white, or any other part surrounded by areas of which the exposure requires to be longer, a piece of black paper or thin card, cut to the suitable outline, is fixed by means of a strip of gummed paper to a loop of thin wire extended so as to form a handle, and is held during part of the exposure so as to shield the part to be lightened. If the wire is sufficiently thin and is held far enough from the sensitive paper, no trace of the handle will appear in the image.
Finally, to darken a portion of the image completely surrounded by areas of which the exposure has to be lessened, a card is used of size large enough to cover the whole of the sensitive paper and in which an aperture of suitable shape has been 774. Excessive contrast in an image can be weakened during enlargement by the following method (0. Mente, 19I0) Before putting the paper on the easel (which latter may be covered with a waterproof fabric) the paper is soaked in a developer, without tendency to give either aerial fog or coloured products of oxidation (a solution of glycin with little sulphite is well suited for this purpose) and thickened by adding some glycerine, glucose, or sugar. After a very short exposure, 2 serving to print only the deepest shadows, the lens is covered with its orange cap and the shadows are allowed to develop. The silver deposit thus obtained very effectively protects the underlying emulsion against the action of light during the final exposure. From time to time a sponge, dipped in the developer and then squeezed, is passed over the surface of the enlargement. According to the effect desired, the exposure may be divided into a variable number of periods, allowing the devel oper on each occasion the necessary time to develop the exposed silver bromide.
775. A very ingenious method for indirectly retouching enlargements has been suggested by C. Duvivier (1924). who got the idea from a method of drawing from a photograph previously described by L. Misonne. A sheet of white paper is fixed on the easel and a sheet of trans lucent paper is placed over it in such a manner that a sheet of sensitive paper may be slipped between them without shifting the tracing paper. Using the projected image as a guide, the tracing paper is covered with pencil work or black chalk.
worked with the stump in all those areas requir ing lightening or masking. After completing this retouching, the sensitive paper is inserted and the exposure is made, the normal exposure being increased to compensate for the absorption of some of the light by the tracing paper. This method is particularly advantageous when several enlargements have to be made from one negative, part of the retouching being thus done once for all.
776. Enlarged Paper Negatives: Equalization of the Grain. Various methods have been sug gested to reduce the grain of the base in enlarged paper negatives. One of the best (Delacre, 1925) consists in exposing the back of the paper (before or after the actual exposure is made on the emulsion side) uniformly, so as to produce a slight fog, compensating for the differences in transparency in various points of the paper. Some tests on cuttings from the paper to be used will show what is the correct exposure for obtaining equality in a paper on which there is no image. Seen by reflected light, such a paper negative appears mottled because there is a dark spot which corresponds to each weak place in the paper base, but if the auxiliary fog is of correct density no trace of any structure appears when the image is examined by transmitted light (the control is more easily done if the image is examined through the paper).
777. Handling of Enlargements of Large Size. When making enlargements of size greater than that of the largest dishes available, it is prac ticable to fold the sheet in two if its smaller side does not exceed the longer side of the dish. Otherwise, the print may be laid horizontally on a boarded or tiled floor, or hung up vertically and covered with developer by means of a brush of soft hairs or by means of a hand atomizer as used by florists. In any case, the print must first be wetted with clean water so as to facilitate the uniform spreading of the developer, and the developing solution must be one of those without tendency to aerial fog or yellow stain (glycin solution with little sulphite). If the print is hung vertically, the developer must be thickened with glycerine, glucose, or sugar. Development must be stopped with an acid bath, and fixing must be prolonged so as to ensure the solution of all the silver salts. Washing is best done with a stream of water directed alternately to one side and the other. If necessary, all the work could be done in the open air at night, the illumination being afforded by an enlarging lantern the nega tive carrier of which has been fitted with a yellow glass or non-actinic yellow filter.