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.
Vignetter. A vignetter is an appliance placed before the lens, which is used for cutting off undesirable foreground. In portraiture it is principally used for bust and two-third figures, where the lower portion is to be vignetted off. The "Morrison" vignetter shown in Illustration No. 15 is made to fit all hand-cameras. Owing to its compactness, it should be included in every home portraiture outfit.
With this vignetter photographic vignettes equal to professional work can be produced. It has all the adjustments of a vignetter for professional use, and can be made to produce the same results. The following description explains the method of its attachment to the camera, also the way to secure the various movements while examining the image on the ground-glass:
267. The up and down movement (by which the foreground is admitted or cut off, as desired) is secured by turning the thumb-screw, while the adjustment to and from the lens is obtained by a sliding friction mechanism.
268. Two cards are supplied, both sides of each being a different shade - varying from white to black - for the purpose of securing the exact shade to correspond with the drapery or color of the background. As will be observed in the illustration, the vignetter fits over the hood of the lens, being adjustable to instruments of any size. In using the vignetter the important points for consideration are: First, the adjustment of the vignetter to the position where it will cut off the required foreground; second, proper blending, as the shade of card in the vignetter must blend with the background; and third, the vignetter must be out of focus to give an even blend. After a few experiments it will be easy to manipulate the vignetter to produce any desired result.
Exposure. Important though it is, exposure is often slighted, to the ruin of final results, even though the subject may have been excellently posed and lighted. Bearing in mind that under-exposure gives contrast, while overexposure tends to produce flatness, it is still far better to err on the side of over-exposure, as it is possible to more easily control the development and secure a good image if detail is present in all portions. If the negative is greatly under-exposed, it is absolutely impossible to secure the desired amount of softness and detail in the shadows, no matter to what extent the plate is manipulated in the development. After the experience of a few trials, correct exposure should be ascertained and future work governed accordingly. Remember, no consideration should be given to high-lights when exposing, but time entirely for the shadows, the proper exposure giving you the required amount of detail.
Development. When developing, carry development only far enough to secure snappy high-lights. They will be of sufficient strength to hold up under the printing light, but not strong enough to produce a chalky print.