VIGNETTERS AND VIGNETTING A vignetted picture softens off gradually until whiteness is met with at the edges. Vignetting is believed to have been introduced in photography by Latimer Clark in 1853, and while it is invariably condemned by artistic workers, it is still popularly considered a pleasing style of finish ing for portrait heads. It is produced by allow ing the centre part to print out while the edges are shielded in such a way that the light gradu ally decreases in actinic power as it reaches the edges. From the diagram it is seen that a vig netted contact print is produced by the diffusion of the light rays as they fall upon the negative with the sensitive paper beneath. Assuming the light rays to proceed from a source r„ their full force acts upon the negative between D and The diffused rays from M, however, act upon the area H and consequently the part between D and r,, is more strongly lighted than the other parts. Also, as the light rays become more oblique, an increased amount of light is lost by means of reflection. The greater the separation, up to a certain point, between the vignetter and the negative, the more gradual will be the merging of the print into a white border. If, for example, the vignetter were lowered or the negative raised to the dotted lines shown the result in the latter case would be that the ;parts between H, and u would be printed strongly and the image would not soften off to H as it would do with a greater separation. In practice, it is found that I in. to i in. is enough for a carte de visite portrait, and from s in. to if in. for a cabinet.
Clark, in the published account of his methods (1853), states that he used a hole cut in an opaque substance placed jc in. above the negative ; the whole arrangement was caused to revolve by means of a bottle-jack to assist the diffusion of the light at the edges.
In 1857, Forrest, of Liverpool, introduced the stained glass vignetter, which is a piece of flashed ruby or orange glass with a colourless centre ; it is usually of the same size as the negative, and is often placed in the frame with it, but it gives softer and better results if laid on the frame in such a way as to increase the space between it and the negative ; being of the same size as the negative, the separation possible is not great. The extent of the clear glass portion is fixed, and in order to do good work the photographer must have a supply of such glasses with different shapes and sizes of openings.
The iris vignetter consists of a piece of vul canised fibre or thin wood large enough to cover the printing frame, and having a central aper ture, round the edge of which is a series of riveted plates, one slightly overlapping the other. The shape and size of the opening are altered by moving the plates.
An easily made vignetter utilises a piece of card or the lid or bottom of a plate box ; it must be large enough to cover the whole frame, and a hole is cut in the centre. This card is laid over the frame during printing, the separation between card and negative being such as to diffuse the light at the edges. To assist in obtain ing a soft edge to the image, the edge of the card may be serrated, and small holes made around the large hole, or one, two, three, or more thicknesses of issue paper may be pasted around the edge of the hole. Of the many other kinds of vignetter only the sand vignetter need be mentioned. A lid of a plate box large enough to cover the frame is taken and the bottom of the lid cut away, leaving a narrow ledge, about in. wide, all round. A piece of plain glass is then dropped into the lid and rests upon the ledges, thus forming a glass-bottomed tray. This is laid on the printing-frame, and fine dry sand is poured into the shallow tray in such a way as to leave a clear glass centre.
Portrait heads make the most effective vig nettes. Dark backgrounds should not be vig netted, neither should Rembrandt and other strongly lighted portraits. When printing vignettes, it is necessary to use diffused light and to select a spot where the light reaches the frame equally from all parts ; the more slowly a vignette is printed the better and softer will be the grading, and any attempt to use strong light or direct sunlight would cause the outlines of the vignetter to show in the form of a well defined line on the print. Should the light spread too much under the vignetting device, place loose cotton-wool between the negative and the vignetter ; but this must be done with great skill, or the wool will form an outline on the print. The above remarks apply to the vig netting of prints made upon printing-out paper in diffused daylight.