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Beneath The Negative Until: 5. Never be too proud to reshoot a poor negative. Did you make an error in exposure? Did your tripod slip and cause a fuzzy negative? Or did you make one of the other dozens of errors which can almost but not quite ruin a negative? If so, do not try to cover up by struggling with the negative by means of darkroom trickery, but instead shoot the picture over again if that is at all possible. To reshoot is to confess a measure of failure to "your client, of course, but you can make up for that by going all-out for a masterpiece on your second try.
To take these small portraits, Disderi first made a wet-plate negative with a special Camera that had four lenses and a plateholder that could be slid from side to side. Four exposures were made on each half of the plate; thus eight poses could be taken on one negative. A single print from this negative could then be cut up into eight separate portraits. Unskilled labor was used for this work; the production of the cameraman and printer was thus increased eightfold.
The technique is based on the property of gum arabic when mixed with potassium bichromate to change its solubility in water upon exposure to light. The more strongly light acts upon the bichromated gum, the less easily it can be dissolved. A watercolor pigment of the type used by painters is mixed with the prepared gum and washed over the surface of a sheet of drawing paper. When dry it is exposed to sunlight beneath the negative until a negative. The image appears when the paper is washed with warm water. |
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