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.
95. It is not the object of this instruction to encourage the under-timing of plates, but to provide the student with a means of treating plates which he finds, upon development, are under-timed. In order to produce the very best results from plates so exposed, they should be treated according to these instructions.
96. Upon reading the title of the instruction, the first question that is likely to arise in the reader's mind is how he is to know before development that the plate is under-exposed, and if he does know, why does he under-expose. Under ordinary circumstances one should aim to fully time all plates. However, there are occasions when one may find it necessary to slightly under-expose a plate in order to produce certain results which could not be obtained were you to give the plate a longer exposure. This is the case more frequently in landscape photography. It will sometimes occur, however, in making portraits; also when children, especially babies, are being photographed, and more frequently when using black backgrounds.
97. In landscape work, for instance, you may be attracted to a pretty view full of deep shadows and strong highlights, which make it impossible to expose for the detail in the shadows and not over-time the highlights. While you can overcome this by cutting the exposure in half, still the plate is under-timed in the deepest shadows and you will have to rely on the developing to overcome this and make a good negative, full of detail and with good half-tone.
98. There are also scenes which the inexperienced worker would consider absolutely impossible to photograph, owing to their peculiar surroundings, and it is just these circumstances that attract the eye and make such a view interesting. The most picturesque scenes are generally the most difficult to reproduce photographically. We will imagine, for instance, a small brook, or a creek, located in some deep ravine, with willows and brush overhanging the greater portion of the water, perhaps with large trees on either side. A stone or rustic culvert crosses the stream, and when the sun's rays fall upon the ripples of water as they roll over the little pebbles and rocks in the brook, they sparkle like diamonds. If one could reproduce, photographically, this creation of Nature the highest attainment of art-photography, as applied to landscape, would be reached. The picture is there; the secret lies in the excellence of the view point and the scientific manipulation of the plate during development. For such a picture, we must first decide upon the best view point from which to make it. Raise or lower the camera to retain the effect of the ripples in the stream. The most rapid plates must be used, and the speed of the shutter must be equal to the motion produced by the running water.
99. In the majority of cases a speed of 1/25 second will be rapid enough, using an open lens. It is advisable to use an open lens, for a small opening would necessitate longer exposure, and stopping down also accents the shadows, makes them deeper and sharper. The aim, therefore, must be to admit of as long exposure as possible, and yet retain the principal point in the view, which in this case is the ripples. The edge of the brook over-shadowed with willows and shrubbery will be quite dark, and to secure detail in this portion of the view would ordinarily require perhaps a full second exposure.
100. The principal point of view in this picture (the running water) cannot be photographed with a time exposure. We must, therefore, make such an exposure as will produce the effect desired in this portion of the picture. As mentioned above, this will require a speed of about 1/25 second with an open lens, to produce the desired effect. It is needless to state that such a view should be made at a time of day when the light is the very strongest in the shadows, for the illumination is weak underneath the willows and shrubbery even when the light is strongest. The sunlight which shines through the leaves is very small in quantity as compared with an open light, and it is simply a matter of utilizing this quantity of light to the best advantage.