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.
Even Illumination. By observing the light at different hours of the day, in any room, you will notice that the entire room is more evenly illuminated at some hours than at others. Then, again, you will observe that one end of a room is better illuminated when the angle of light leads towards that particular end; also, that this same end, or corner, of the room is less illuminated when the angle of light is reversed. These important matters, which persons of little experience are quite apt to overlook, have a vital bearing on the making of satisfactory pictures.
107. The matter of direction of light does not pertain alone to cases where windows are admitted into the view, but even where they are excluded. The direction of the light supplying the illumination is the same, and has exactly the same effect whether windows are admitted into the view or not.
Theory Of Special Method Of Developing. By the Special Method of Developing it will be learned, by reference to that lesson in Chapter XIII (Lesson Vii. Modeling The Forehead. Practice Work) (Lesson Vii. Modeling The Forehead. Practice Work), Volume II, that we calculate on ample exposure to fully time the most dense shadows. You will learn that we register upon the plate all the exposure necessary for detail in these shadows, at the same time being aware that the high-lights (the windows) are many times over-exposed; so it is necessary to hold back the high-lights and develop the shadows.
Use Of Alkali. Carbonate of Soda opens the pores and permits Pyro to penetrate the film. Without some alkali the Pyro will not act. If the shadows can be developed along with the high-lights, exactly what you see in the view can be retained, which is the object of this developer. But, the developer is helpless without sufficient exposure. Combining the two will control the high-lights, as only sufficient alkali (the detail-producing chemical) is used to develop the shadows. The amount employed is not enough to build up, or clog, the high-lights, so they are held down until the shadows are fully developed. A few drops of alkali should be added from time to time, until the entire plate is developed.
The Result. When the, shadows are clear and crisp - full of detail - and are registered exactly as viewed on the ground-glass, then you have a true record. It will be found that this plate is free from all halation, and that even in the strongest high-lights the lace curtains on the windows show every line of design as soft as though an exposure had been made on them alone.
Practice Work. It is advisable, for the benefit of the experience you will derive from this experiment, that you expose one plate in the ordinary way and develop it in normal developer, using the Universal Developing formula. Expose another plate, giving four times the exposure, and develop according to the methods for Special Development. Compare the results, which should convince you as to the value of this method of treatment. For all your worthy work, where strong lights, such as caused by admitting windows into interiors, are to be contended with, use this method. Make proof prints from both of the above plates mentioned, noting all necessary data on the back of each, and file in the proof file for future reference.
Note. While non-halation, or orthochromatic, plates will give better results in this work than the ordinary fast plate, for first experiments use the ordinary plates, as they are more easily judged in the development. Other experiments may be made later with the special plates, which, if properly manipulated will give still better results. However, use ordinary plates for first work.