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.
Making Exposure. After everything is ready do not hurry in making the exposure. Take time, yet do not work unduly slow, as the subject will likely become tired. Hurry only excites the sitter, making it impossible to secure a pleasing expression. Take hold of the work in a manner indicating that you know exactly what you are doing, and above all things have confidence that you are able to secure the results attempted, and that you do know your business. If you lack confidence in yourself, it can hardly be expected that your subject will have confidence in you.
159. When everything is ready close the shutter, insert the plate-holder and withdraw the slide. Then, glancing quickly over the subject to see that everything is as it should be, have the eyes turned in the direction desired. If possible, hold the attention of the subject by talking, but never ask a question or say anything that will require an answer, or make it necessary for the subject to talk just at the critical moment, unless you desire a change in the expression of the lips. Then a query requiring a short answer - yes, or no - will be in order.
160. When the expression is as you desire it, quickly press the bulb, making the exposure. The exposure should be made in an apparently careless manner. By no means hold the bulb in front of you, giving it a hard squeeze as if your life depended on it. The bulb may be held behind you, in your pocket, or in any careless position, and pressed in a manner not to attract the attention of the subject. These are little points, but they are very important in obtaining proper exposure. It is the many little things which make or mar successful portraiture, and fully as much attention, if not more, should be given to obtaining expression as to any other feature of the work.
Developing. Although you have exposed for shadows, yet you must develop for high-lights. Considering the plate full timed, it is well to start developing with a little old, or once used, developer added to the fresh solution. This old solution acts as a restrainer, holding the plate crisp throughout the development. As soon as you find the shadows are developed, turn your attention at once to the high-lights. Are they holding their relative values with the shadows? If so, as soon as they show the proper strength-allowing for a trifle to be lost in fixing-remove the plates from the developer, rinse and fix at once. For further instruction for developing see Volume II.