A Simple Fixed Focus Copying Camera
Stephen S. Hoyt
A VERY useful and convenient copying unit for the darkroom can be easily constructed from a packing case and an old lens. Two porcelain wall sockets, electric cord, a switch, and some tin for reflectors complete the list of necessary parts.
The size of the box is first determined by the size of the image desired. Two photographic printing frames will be required, one to hold the copy, and the other for the sensitive material which may be either film or paper. For an 8 x
10 image, a lense of about 9-inch focal length when stopped down to about ƒ 32 will cover the plate.
The distance between the lens and copy can be roughly measured by focusing the image of a light bulb on a piece of white cardboard. This distance is then doubled and the box built accordingly. The lens board with lens in place should be nailed in correct position only after a final adjustment of the focus is secured. This is done by placing a piece of groundglass in the printing frame that is to receive the sensitive material. Be sure to have the ground side of the glass out. After sharply focusing the image, the position of the lens board is marked and nailed in place. The lens is then stopped down to a smaller opening which will take care of any discrepancy in focus adjustment. A printed page inserted in the copy-holder frame while making the adjustment of focus is better than a photograph for this purpose.
The lid for the box should be built with a small cleat all around to prevent light leakage, and should be fastened in place with four screws. The ventilator should also be built with care so that too much light does not escape. The exposure is made by turning the lights on and off, thus eliminating the necessity for a shutter.
By unscrewing the printing frame from the lighted end, the apparatus can be used vertically for copying sections of large maps, drawings, and book pages which will not fit into the printing frame. Two 60watt frosted lamps will provide ample illumination for a 5 x 7 copy. An 8 x 10 apparatus will require two 100-watt lamps.
If a paper negative is desired, bromide paper, Kodaline process paper, or Kodalith tracing cloth can be used as the sensitive material. Enlarging papers of the gaslight variety are slower and therefore require somewhat longer exposure but produce the best results. They can be handled under a fairly bright yellow safelight.
When a black-and-white copy is made on paper, a positive can be made either by re-copying in the camera, or by contact in the regular way. Because of the fine grain of the present day printing papers, they will be found satisfactory as negatives; and where s"~ed is essential they can be washed and dried in less time than film.