VIGNETTING.
For a long time the means of producing this pleasing effect was known only by a few, and was sold as a secret process for large sums. There are now known many ways by which it can be produced. Before describing these a few words are necessary as to the nature of sub ject which is best treated in this manner.
Both landscapes and portraits make excellent vignettes if certain conditions be observed. The first of these is that the negative be one which may be described as delicate,—that is to say, it must be full of detail and at the same time without excessive contrast in large masses of light and shade. A negative which might otherwise be considered slightly over-exposed is excellent for a vignette. Another necessity is that there should be no very deep shadow of great extent, which in an ordinary print extends over the portion which is fully printed and into that which in the vignette is to be white margin. With such deep shadows it is impossible to avoid an abrupt transition from dark to white, and the delicacy of the vignette is destroyed. For this reason a portrait with a dark background is not suitable for vignetting, nor is a head and shoulders of a sitter with a dress having a very dark body.
We will take first of all the case of a landscape, and describe how the first experiments may be made. A negative showing the qualities which we have described is taken. A piece of ordinary cardboard is cut into such a shape and size that it will cover the whole front of the frame. From the centre of this piece of cardboard there is now cut an oval hole about two-thirds as long as the length of the plate and also two-thirds as wide as its breadth. The following cut will give an idea of the relative sizes of the hole and the plate. The outside line shows the whole extent of the piece of pasteboard, the clotted line shows the size of the plate, and the oval portion is that which is removed. It is not necessary to draw the oval with any degree of accuracy. A rough
line such as we show is quite good enough.
The piece of cardboard is fixed to the frame. This may be done either by means of a little glue or by drawing pins; the latter method is the best. Printing is performed in diffused light, or still better in sunlight, a piece of tissue paper being placed over the opening. It is necessary to get a broad expanse of sky opposite the frame to produce good vignettes if diffused light be employed. The reason of this is evident. The shading off is produced by light which passes angularly under the edge of the opening in the pasteboard. Now it is evident that if there be not plenty of light striking the frame obliquely no rays will pass beyond the edge of the aperture in the pasteboard. It is therefore necessary if, as sometimes happens, espe cially in a town, a light from only a narrow portion of the sky can be obtained, to use tissue paper over the opening even when we are printing by diffused light. The effect of the tissue paper is to produce artificial diffusion spreading the light in all directions.
It is best to cut the oval opening somewhat too small at first, and after a proof is taken, or even when the first is in progress, to alter it as appears desirable.
The first proof that is taken will show whether the arrangement of the pasteboard is correct. The distance between it and the negative should be for small plates half to three-quarters of an inch, for large plates pro portionately more. With this distance between the vignettes and the glass the shading off should be soft enough, but sometimes it happens that it is not. In this case the following course may be pursued. The edges of the cardboard are taken between the finger and thumb, and are bent upwards as far as is possible without pro ducing wide cracks. The section of the cardboard will then be something like the following. We have tried to show it as if it had been cut into two pieces, one only of them being represented.