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.
Library by the Cramer Dry Plate Company.
552. Consider it an axiom that the perfect negative is the result of proper lighting and normal exposure, and that such a plate can only be ruined in the dark room by gross carelessness. Also that no juggling with developers will compensate for carelessness in lighting or exposure. It is self-evident that if there has been no exposure there can be no development of an image, also that if there has been insufficient exposure or hard lighting, satisfactory results cannot be obtained, though if the exposure and lighting have been within the latitude of the plate used, skillful handling of the plate during development will give satisfactory results.
553. Train yourself to be careful, accurate and cleanly, and so reduce probability of error to the minimum. A dry plate is a very delicate and sensitive chemical product, and should be handled so as to eliminate all danger of chemical or light fog. When a shipment is received, store the plates on edge, (to avoid pressure) in a cool dry place, away from strong light, and free from the influence of sewer or illuminating gas. When opening a package, and filling plate holders, keep well away from the dark room light (some brands, notably the Trichromatic should be placed in the holders without any light being used, and in a perfectly dark room).
Close the holder and the plate is then ready for exposure in the camera. The first plate in an original package is face down, the second face up, the third face down, etc. Be sure before leaving the dark room that no packages of plates are open, and that all holders are closed.
Speed Of Plates. The Crown and the Instantaneous Isochromatic are the two fastest brands made, and for all practical purposes when used under the same conditions, can be considered as of equal speed, and either of these brands should be used for all rapid exposures.
Exposure. Correct exposure, or exposure within the latitude of the plate is of vital importance. Time spent in becoming familiar with your lens, plate, light conditions, lighting of subject, etc., is well employed. We would advise all outdoor workers, and those making interiors, to become familiar with, and constantly use a good exposure table, or exposure meter. Its use will enable you to be more certain of the exposure needed under all light conditions for all subjects, at all times of the day and year, and you will have the satisfaction of bringing home plates that will make good printing negatives.
557. For exposures under the skylight nothing will take the place of experience; money spent on a rapid lens, and time spent in keeping that lens perfectly clean, are both well invested. For cleaning the lens take water three ounces, grain alcohol one ounce, nitric acid three drops. After dusting the lens rub with an old clean cotton cloth wet with this solution, and polish with a dry piece of the same cloth.
558. The light should fall on the sitter at an angle of forty-five degrees, and except for special purposes, there should be no violent contrasts between the lights and shadows. Illuminate the shadows sufficiently to balance the lights, or cut down the volume of light falling on the skylight side of the subject by means of a screen so that the lights will balance the shadows. This, and correct exposure, are the only ways to obtain negatives which will please the great majority of the picture buying public. In making white draperies do not flood them with light if you want detail, nor on the other hand do not keep their tone so low that there are none of those little crisp highlights which add so much to the quality and beauty of the negative.
559. By study and by test become familiar with the light effects obtainable under different portions of your skylight, bearing in mind that under an open light the nearer the subject is to the side light, the more violent the contrasts, while further away they are less. Learn the difference in exposure needed with the different diaphragms, and with the same diaphragm when making a large head and a full figure.
560. The latitude of Cramer plates is so great that if two seconds were the normal exposure, under certain conditions, an exposure of either one second or of four seconds would yield a satisfactory printing negative, if properly developed. Do not abuse the power this latitude gives, for unless you are willing to vary your treatment of plates with extremes of exposure, you will be disappointed in the results obtained. Strive for an even quality of negatives the year round, and the printer shall rise up and call you blessed.