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PKACTICAL LABORATORY OPERATION 42]
A good duplicate negative requires raw stock of the highest resolving power practicable. It should be the very best intermediate film copy that we know how to make — almost regardless of cost. Since it may be used to make several hundred prints, it would seem practical to spend almost as much money to correct a deviation in the dupe from that which is considered ideal as can be spent to correct that same deviation in each and every print to be made. In a sense the relationship of a dupe to a film laboratory is similar to that of special production dies, jigs, and tools to a mechanical factory. The automobile industry long ago pointed out the business wisdom of buying costly but accurate tools for the mass production of products of high mechanical quality. Where the mass production of high quality prints is the objective, it would seem to be similar business wisdom to determine what is the best dupe that can be made almost regardless of cost — and to go ahead and make it. Should an error or deviation be found in a dupe that has just been made, it is wise to scrap the defective dupe and to make another that eliminates the defect.
The raw film most suitable at present is Eastman 5203 duplicating negative. A good procedure is to print this film on a step-contact printer. Although such a printer is slow when compared with commercial continuous printers, the quality improvement should be observable in the release prints. As used commercially in one laboratory, the film is developed in a glycin developer at a relatively low gamma, yielding quite high-speed developing (compared with negative developing times) . The cost of the dupe negative is correspondingly low and the resolving power and graininess quite low compared with the more customary 6-min. developing time in Kodak SD-21 developer at a development gamma of about 0.65. Because the effective speed of the film is materially reduced by the reduction in development gamma, appreciably more light is required in the printer for proper dupe negative exposure and the running speed of the film is comparatively slow in the printer.
Only fine-grain release print raw film should be used. The dupe negative has been made for one-light printing, and no light changes are required during the release printing operation. If high printing speed is required to obtain low printing cost, a continuous contact printer may be used. If somewhat better picture quality is required, a step-contact printer may be used, resulting in lower speed and somewhat higher print cost. At present, DuPont 605 A would seem to be the preferred raw stock due to a difference in the shape of the toe of the H and D curve; East