This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Full Explanatory Details Of Home-Made Enlarging Apparatus Without Condensers. (A) electric light;
(B) cone of enlarging apparatus; (C, D, E, F) the four ground-glasses in position; (G) door-hinged at the top; (H) 8x10 kit for 5x7 plates. 8x10 plates are inserted in this same slot without using any kit; (I, O) the upper and lower catches which are on back of the camera, which originally held the ground-glass frame in position, but now utilized to hold the back of the camera to the enlarging box; (J) casing or flange between the cone and the box containing the ground-glasses; (K) flange between box containing ground-glasses and back of camera; (L) back of camera; (M) frame for holding orange colored glass; (N) orange colored glass partly withdrawn.
639. When completed the exterior of the cone and the balance of the apparatus should be painted black, while it is preferable to paint the inside of the cone white, so as to reflect all the light possible onto the ground-glass.
640. If this apparatus is made for 8x10 negatives, a kit should be constructed to hold 5x7 and smaller negatives. A regular nest of plate-holder kits may be purchased from any supply house, and these used when it is desired to enlarge from negatives smaller than 8 x 10 inches. The largest kit is slightly beveled on the upper and lower edges to fit the grooves, and 8 x 10 negatives are slid in the grooves without a kit.
641. If it is necessary to secure full detail and have a perfectly even distribution of light over the entire surface of an 8 x 10 plate, four ground-glasses should be used. When smaller negatives are employed, two, or even one, ground-glasses usually will be sufficient to give the proper distribution of light. The amount of diffusion necessary depends entirely upon the character of the source of light.
Use Of Camera With Daylight. If desired, this apparatus can be used for daylight work- i.e, daylight may be employed as the source of illumination. In this case, the window will need to be blocked leaving an opening in it 8 x 10 inches in size. The cone will need to be removed and the balance of the apparatus placed firmly against the opening in the shutter. The same number of ground-glasses should be used, however, as when artificial light is employed.
643. Always strive to have the light entirely unobstructed. If a building should be opposite your window there would be danger of uneven illumination and it would, in that case, be advisable to place a white cardboard, two feet square, just outside of the window, at an angle of 45°, so as to reflect light from the sky onto the opening. This will give perfectly even illumination.
644. While the professional photographer should have an enlarging apparatus 8 x 10 inches in size, the amateur, or those who have no large camera and desire to construct a smaller apparatus, can do so by using the regular hand camera in place of the view camera and following out the above plans and suggestions. When the small camera is used and artificial light is to be employed the cone will not need to be so long, as the length of the cone depends upon the size of the largest negative from which it is desired to make enlargements. The light, however, should always be as far from the negative as twice the diagonal of the negative.
Lens Screen. In making enlargements it is very desirable to have some arrangement that will facilitate the correct placing of the paper on the easel. A simple attachment can be constructed on the lens, similar to the one shown in Illustration No. 18 (M and N), which permits of an orange or ruby glass being placed in front of the lens, through which sufficient non-actinic light will pass to enable you to see what you are doing. After the image has been sharply focused on the easel, the ruby or orange glass is inserted in the groove, and sufficient light will come through this screen to form a slight image on the easel, yet not enough to fog the paper. The attachment shown in the accompanying illustration is made of a wooden block, with a hole cut in the center, and this is fitted over the lens. A groove in the front of the block is made and the yellow glass inserted in this. When the exposure is made this glass, of course, is withdrawn and again inserted at the end of the exposure.