[CHAPTER XII.]
VIGNETTING
Of the many varieties of small portraiture, the vignette is, perhaps, the most popular, and, when well done, is certainly the most refined and delicate. Two things are to be especially avoided in vignetting. The form of the vignette should not follow the form of the figure closely, as it is too often made to do, and dark backgrounds should not be employed. The qualities to endeavour to attain are softness of gradation, and an arrangement of the forms of the vignette that shall throw out the head and figure, and the resulting print should somewhat resemble a sketch, finished if you like, but sketchy in effect. Although the background should be light, it ought not to be white, but of a tint that would just throw up the white of a lady's head-dress. If the background screen could be painted so that a little shade should appear over the shoulders of a sitter for a head, or rather darker behind the lower part of a three-quarter figure, so much the better would be the effect. It would be difficult to find a case where gradation could not be of advantage in a background; however slight, it conduces especially to relief.
Having stated what should be aimed at in vignettes, we now come to the technical methods of producing them.
In many cases vignetting is considered to be a merely mechanical operation, and very often looks like it. Perhaps the trade have more to answer for than the printer, since the qualities of the wares advertised for the use of the vignetter are often exaggerated to such a degree that they are supposed to be suitable to any pictures. Vignette glasses are not so common as they used to be, but they certainly are useful in some instances; we almost think that the methods of producing vignetting apparatus which will be described shortly, superior to them. In case the printer should wish, however, to use these glasses, here is a method by which he may produce them. Have a piece of orange glass, flashed on one side only, rather larger than the size of the picture to be vignetted. Take a rough print, and trace round, in the proper position on the glass with an ink line, the point to which the picture should extend. This should be marked on the unflashed surface of the glass—that is, the surface on which the glass is uncoloured. Place the plate so marked on a white surface, flashed side uppermost, and make a solution of hydrofluoric acid and water, 1 part of the former to 3 of the latter, in a gutta-percha dish or bottle.[22] Make a pad of flannel and cotton wool at the end of a stick, about the size of a large nut, and drop this into the solution. Dab this on the coloured surface of the glass in the central portions where the print is to be completely printed in, gradually working out to the inked line. Always work from the centre to the edges, and dilute the acid with a little water as it approaches the margins. By degrees the flashing will be dissolved away in the centre, and, if properly performed, the colour will gradually be eaten away, till the glass is colourless in the centre, and keeping its full shade of orange at the ink lines. The glass is then washed, and is ready for use.
The most popular plan of vignetting is with cotton-wool. We believe that the greater part of the vignetting done in England is by this clumsy, costly, and difficult method. It requires more time and attention than any other way of producing the same results. Its advantages are, that it is more "elastic," and allows the operator more scope for attention than other methods. In the hands of a person who has very great skill, taste, and patience, it is undoubtedly most useful; but when used by anything lower than the highest skill, the results are almost always hard and inartistic. The operation is thus performed. A hole is cut in a piece of cardboard, which is placed over the negative. Under the edges of the cardboard is placed cotton-wool, which is lightly pulled out, so as to slightly shade the vignette, and produce the vignetting gradation.
The next methods of vignetting are dependent on simple laws of optics. Suppose you cut a round hole in a card, say, half-inch in diameter, and so arrange it that all the light getting to a sensitive paper comes through this hole, and that the card is for our experiment placed half-an-inch from the paper. Now place the hole so as to face the sky, but so as the sun has no direct rays falling through the hole. It will be found that the greatest darkening will not occupy a space exactly opposite the hole, but be away from the side on which the light is brightest. The dark round patch will be shaded gradually off till a line is reached where, practically, the light has no effect—that is, if the surface of the card next the paper be blackened. It will be noted, however, that the shading is not equal on both sides, but that the gradation is most extended away from the side on which the light is brightest. A good example of what is meant will be to try the experiment of placing the paper and card flat on the ground in the angle between two walls, both of which are in shadow. It will be seen that the brightest gradation takes place in the direction exactly away from the angle of the walls. Next repeat the experiment, making the hole point to the sky, which is equally illuminated and pointing well away from the sun. It will be found that the gradations are equal, and the greatest darkening exactly opposite the hole. Raise the card next to the height of one inch, and the gradations will be found to be more extended and softer. The reason of this can be well understood by a glance at the figures. In both, suppose A B to represent the section of the card, and C D the hole in it, and the dotted circle the sky, and E F the paper. Take the points a, b, and c on the paper, and let us in the three instances see what relative illumination they will receive. a is opposite the hole, and receives the light from a circle of sky of which d e is diameter, and b from an ellipse of which h k is one diameter, and e from an ellipse of which f g is one diameter. In the first case, where the card is 1/2 inch from the paper, h k is about one-fifth of d e, and g f about one-third of d f, and since the ellipses vary as their two diameters multiplied together, the point b would receive only one-twenty-fifth the light that a received, and c about one-ninth.
Fig. 21.