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A Negative Copy: The dots appear in varying size, depending on the tones of the original photographs. A negative copy of the picture is first made with a camera, inside of which is fitted the halftone screen. This negative is then printed on a metal coated with bichromated gelatin. The dots on the negative allow light to penetrate and render the glue insoluble, so that when the plate is etched with acid each single dot remains on the surface of the plate, which is then mounted at type height on a wooden block. In the final print the minute clusters of dots cannot be distinguished, but appear as tones of gray.The best Camera for the job, all things considered, is a 4x5 view camera, but many photographers prefer the convenience of working with a 4 x 5 press Camera for most of their setups, using a view Camera only where the corrections! or the long bellows are called for. There was a time when the 8 x 10 was the standard instrument for industrial photos,! but that's no longer the case. The 8 x 10 speeds production of prints in the darkroom, but slows production of negatives on the job. In those cases where a big production of prints is necessary, the method used by some large companies is to shoot the picture on 4 x 5 anyway, have one perfect enlargement made, then copy the enlargement on 8 x 10 film and use the copy negative for making as many contact prints as are required.
Talbot visited Herschel on February 1 and learned of this fixing technique. He described it, with Herschel's consent, in a letter published in the Compte-rendu of the French Academy of Sciences.23 Daguerre at once adopted it. Almost all subsequent photographic processes rely upon Herschel's discovery. Herschel, who was something of a linguist, also proposed "photography" to replace Talbot's somewhat awkward phrase "photogenic drawing" as well as "positive" and "negative" for "reversed copy" and "re-reversed copy." These words were quickly adopted universally. |
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