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Weak Negative: He bathed paper with a weak negative solution of common salt (sodium chloride) and then, after it had dried, with a strong solution of silver nitrate. These chemicals reacted to form silver chloride, a light-sensitive salt insoluble in water, within the paper structure. He placed a leaf, a feather, a piece of lace in contact with this prepared paper and exposed it to sunlight. Gradually the paper darkened wherever it was not protected from light by the opacity of the object in contact with its surface. The result was a white silhouete against the dark ground of the blackened paper, or shadowgraph. Today we should call this a negative image. As early as February 28, 1835 Tal-bot described how a positive image could be made from the negative. He entered in his notebook:
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. |
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