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.
Copying Prints For Lantern-Slides. Carefully follow the instructions given in the lesson on copying, and strive to produce negatives that are crisp, not flat. Negatives must have a trifle more contrast than ordinarily. Use a little Bromide in the developer, so as to produce clear shadows and snappy high-lights, and develop to good strength. Be careful to overcome as much as possible the grain of the original picture being copied. Remember that from a flat, weak picture a snappy, brilliant slide can not be produced, but by accurate exposure and restrained developer the contrast of the original may be improved.
Developing Negatives To The Proper Strength. Develop the negatives according to the exposure. If it is slightly over-exposed, treat it as such, and aim to produce snappy, brilliant negatives, slightly over-developed.
Results Flat When Making Lantern-Slide From A Large Negative. Simply follow the instructions for excluding all light other than that which is admitted through the negative to be copied and there will be no trouble in overcoming this difficulty.
Focusing. It is absolutely necessary that the image be extremely sharp; therefore use a magnifying-glass to examine the image on the ground-glass, and get it as sharp as possible, if necessary introducing a smaller stop to produce absolute sharpness.
Judging Correct Exposure. Only practice and close observation can teach this. With a few experiments, noting carefully the conditions of light, etc., this difficulty will soon be overcome. It is advisable to use a test plate, giving portions of the plate different lengths of exposure. Then develop the plate and one portion should be found very nearly correct, sufficiently so to guide in the final exposure.
Obtaining Correct Size Of Image On Lantern-Slide When Making Slide By Reduction. Remember that placing the camera nearer to the negative will produce a larger image, and further away, a smaller one. With a little practice, the camera can always be placed so as to produce the proper size image.
Judging Proper Development. Only practice and close observation can teach this. The experience had in developing ordinary plates should help to overcome this difficulty. It is almost impossible to state just how long or how far it must be developed. Remember that lantern plates must not be as hard and strong as negatives. Develop only until full detail and fair crispness are obtained, then the plate is fully developed.