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.
Methods Of Vignetting Portraits And Eliminating Undesirable Portions Of Any Negative. The methods that will be described are thoroughly practical. While the last method requires a little extra work to prepare, most effective results can be produced through its adoption.
801. The first method is to take a piece of cardboard a trifle larger than the negative you are printing from. Cut a hole in this board a little smaller than the portion of the negative you desire to show in the print. (See Illus. No. 9 1/2, Page 157.) Next make small notches like saw-teeth 1/4 to 1/2 inch deep in the edges of this opening. The saw-tooth effect will blend the light which falls upon the negative because the light will filter in between the teeth. More blend can be produced by holding the cardboard a greater distance from the negative. About 1/2 inch from the negative is as close as the work should be performed. The cardboard must be kept in motion during exposure (a circular motion is best). See that the card completely covers the parts of the negative that are not to show in the print.
802. A slower method, slow in printing, but which will do away with the necessity for keeping the vignetting card moving, and will produce soft results, is to build up the cardboard one-half inch from the negative and fasten to the printing frame, covering the opening with a fine quality of white French tissue paper, or onion skin, which can be purchased at any photo supply house. If the negative is thin, use light blue tissue. Blue will cause the negative to print slowly, but the resulting print will be stronger.
803. A simple way to arrange this vignetting device so it can be fastened to the printing frame, is to take the cover of a dry plate box, large enough to practically cover the printing frame. Cut into the corners about 1/4 of an inch. Make a light cut from corner to corner on both ends and sides, so they can be bent outward, forming a lip, which can be tacked to the printing frame. Next cut a hole in the cover, as described in making the vignetting card, and cover with tissue paper. Several vignettes can be made different sizes and shapes. One or the other will fit any ordinary negative you may wish to vignette.
804. Another method of vignetting, and this is especially intended for portraits, is to paint the film side of the glass with opaque. See instruction for making opaque, in Chapter XL (Dodging In The Printing), Dodging in the Printing, but when applying this method, instead of blending you merely block out undesirable portions, and the blocking out must be done in an irregular way - sort of hatch or design shape - to give the appearance of brush developing, as though the print had been developed with a brush, swabbing backward and forward. This method is best applied where white or very light grounds are used.
805. The third method is to produce a vignette effect by simply developing the parts of the print that it is desired to show. This, as before stated, is a much more difficult process, but with practice and care fine results can be produced with it.