ENLARGING NEGATIVES In order to make a large negative from a small one, two operations are necessary. A trans parent positive must be made from the original negative, and from that a new negative can be made by enlarging to any desired size. The character of the transparent positive is of the greatest importance in determining the character and quality of the new negative. The extreme shadows or densest parts should be moderately strong, but such an exposure should be given that the highest light is veiled. No part should be quite clear, and the transparency should be dull rather than brilliant. The best method for making the transparency is by contact printing by artificial light on a rapid plate, thus securing the truest reproduction of the gradation of the original. For the same reason—the desirability of reproducing all the gradations as correctly as possible—the enlarged negative should par take of the same character ; the deepest shadow should be veiled, otherwise there will be a dis tinct loss of tone values. The method of working is given under " Enlarging by Daylight " and " Enlarging by Artificial Light," excepting that the transparent positive is placed in the position there described for the negative and a plate in the position given for the sensitive paper".' Backed plates should be used for making the transparency and the enlarged negative, and the film side should be towards the lens in each case. Film towards film is the rule, as in printing. An exception to this is when a reversed negative is required for the carbon process. In that case the transparent positive is reversed in the carrier, the glass side being turned towards the lens.
Enlarged Paper nega tives may be made on bromide paper from lan tern slides or other transparencies, the bromide paper after exposure being treated with a weak bichromate solution, as described under the heading " Sterry's Process," in order to obviate harsh results. By the W. Coats method, an
enlargement is made on rapid smooth bromide paper, the exposure being short so as to keep the shadows clear ; amidol is used as the developer and the print is washed for two minutes ; the unfixed print is then toned in the following bath, in which it should remain for seven minutes, at least : A. Pot. ferricyanide . 4o grs. 8 g.
Glacial acetic acid . oz. 5o ccs Water . . . ro „ 1,000 „ B. Uranium nitrate . 4o grs. 8 g.
Glacial acetic acid . # oz. 5o ccs.
Water . . . 10 „ I,000 „ Take equal parts of each just before use. The solutions keep well separate, but not when mixed. When toning is complete, the print is well washed and immersed for one minute in a solution of zo grs. (4 g.) of ammonium sulpho cyanide in zo oz. (r,000 ccs.) of water. The print is washed again for two minutes and then exposed to 4 in. of magnesium ribbon burning at a distance of I2 in. from it. The print is next rinsed and redeveloped in the original amidol developer, fixed in redeveloped hypo," and washed.
A metol-hydroquinone developer has been sug gested in place of the amidol.
An important point which must not be over looked in all enlarging processes is the increase in contrast in the resultant print or plate. This is caused by the scattering of the light by the silver grains of the negative, which practically act as points from which the light spreads or scatters out in fan-shaped bundles, and there fore does not reach the lens. This may be over come by placing the negative film side next to a sheet of fine matt opal glass.