Production Of Duplicate Negatives

To produce a negative of equal size from a negative, the Eder-Pizzi-ghelli formula is for the amateur probably the simplest. For this purpose an ordinary thin film is bathed for two minutes in a solution of

Bi-chromate of potassium 10 gr.

Water 250 gr.

and the same is thus left suspended in the dark room to dry. The negative, which we obtain later on upon the film, is reversed. The application of films instead of plates has the advantage that, when printing the duplicate negative it can be inserted from the reversed side and a correct print can thus be obtained. After the chromated plate has become dry it is printed under the negative to be reproduced. Expose until the details of the picture can be seen and then wash for an hour. Now put the film into one of the usual developer solutions - hydrochinon, pyrogallic acid, or oxalate of iron, and thus a negative is obtained. The process is, that the exposed parts thrust off the developer solution, as the same acts only upon picture parts of very little or no exposure. Finally, the plate is put into a fixing soda solution and washed as usual.

To avoid halos on interior exposures, when windows are in the line of the objective, the following method is recommended. To avoid the over exposure of the window, particularly when a fine landscape is visible through the open window, make first a short exposure for the window. Close now the shutters and darken the room as much as possible and make a flashlight exposure of the interior without changing the position of the camera. The natural and artificial illumination should, of course, agree as much as possible. If the plate is now developed, it will be seen that landscape through the window and interior have obtained the correct exposure. In case there are no shutters the interior exposure may be done after nightfall. If plates are used for this work which are strongly colored yellow in the emulsion, a satisfactory picture will be the result.