METHODS OF VTGSTTTING.
For the purpose of vignetting there are practically four devices in use ; the first, Fig. 239, consists of a piece of flashed glass with a colourless centre. Flashed glass is prepared by taking up a ball of molten colourless glass on the end of the blowpipe, then dipping it in a molten coloured glass for a few seconds and blowing the two together, so that the colouring matter exists on the surface riveted flaps, cut as shown in Fig. 241, and fitted together as in Fig. 240, each one slightly overlapping the next. The flaps are folded back or brought forward according to the desired shape of the vignette. This certainly has the advantage that it may be repeatedly adjusted, and of all ready - made vignetters is the most satisfactory. Zinc vignetters, which consist of a sheet of metal with a centre opening, are often useful. When their edges are serrated, as shown in Fig. 242, they may be turned outwards ; this tends to soften the shadows thrown. These vignetters have the advantage of durability, as have also the wooden vig netters shown in Fig. 243. These are made in wood about half an inch thick and bevelled inwards. Another method of vignetting at one time practised by amateurs is by means of cotton wool. A sheet of wool of sufficient size is cut off and an Opening made in the centre. The wool is pulled out loosely around the edges. Black wool is preferable, as it stops a. little more light. Generally speak ing, the method is unsatisfactory, as the vignette is so liable to disturbance and purchased, but made as required. This is the practice adopted at all large printing establishments. The printer takes a sheet of card about the size of the outside' dimensions of his frame, and on this he sketches roughly in pencil the shape is to take, or rather the shape it will be necessary to give to the rignetter to produce that effect. The opening must be made somewhat smaller than the desired effect on the print, to allow for spreading. Now, the amount of spread ing, and therefore the degree of softness, will depend upon the distance the vig nettes is from the negative, and the kind of illumination which the negative is to receive. This is the point where the majority of inexperienced workers stumble, the vignetter being mistakenly fixed too is not sufficiently opaque. In commercial work also it is essential that the vignetter should be of a permanent nature to ensure each print being alike. A great deal of discussion has taken place as to the shape and method of cutting the vignettes ; some workers punch a hole with a gouge to the shape shown in Fig. 244. Others contend
that such edges have practically no effect on the result, provided the vignetter is put at sufficient distance from the negative. The form the vignette should take is governed by the tones of the picture, so that it may not spread un equally in any direction. Generally speaking, it should not repeat the outlines of the figure, nor should it be tied down to any arbitrary shape. For this reason, therefore, vignetters should seldom be close to the negative. A moment's con sideration will show that the farther the vignetter is from the negative, the greater the spreading of the light, and that the farther the light spreads the more deli cately must it shade off from one tone to another. Moreover, where the source of light is small, such as that used when printing bromides, a sharper shadow will be cast. Where the source of light is large, that is, where diffused light is used, such as ordinary daylight, the vignette will be more inclined to spread unequally. It will have been seen that the thinner the negative the inure the light will stray ; such portions require more shading—that is to say, the vignette must come a little closer, and in extreme cases it is even necessary to lay a little cotton wool over the part. The cotton wool must have the softest possible edge, which may be ob tained by pulling it out loosely. One kind of vignetter consists merely of one half of a plate box, the corners of which are broken open so that when tacked to the frame it stands out from it as shown in Fig. 245.
sufficiently, and it is always as well to cut them too small to begin with, he breaks or cuts away portions until the desired result is obtained. The effect is judged better by looking at, say, a ground glass window, and at any rate it cannot be well estimated by looking at a bare gas flame ; half closing the eyes gives, also, a more correct idea of the spread of the vignette. If the printer detects any thin shadows which appear likely to spread unequally, he tucks in a little Another form of which this is a modifica tion is shown in Fig. 246, also made to stand out. It is cut from one piece of card, scoring on the dotted lines shown so as to bend into the shape indicated. An excellent arrangement for vignetting, having a muslin frame for diffusing the light, and allowing the Vignetter to be adjusted in any desired position, is shown by Fig. 247. It is known as Salmon's Vignetter, and is obtainable at any photo graphic dealer's.