Ordinary focussing cameras may be converted into fairly efficient enlarging lanterns with the expenditure of a few shillings. There is the ellipsoid reflecting lantern, or a lantern with condenser attached, either of which can be readily clamped on to the back of a camera of corresponding size of plate, and both systems are constantly undergoing improvements.
Enlarging Easel.—A good easel consists of a board provided with a detachable hinged frame holding a sheet of plate-glass, behind which the bromide paper is kept perfectly flat. For convenience it should swing, in cases where, for the correction of lines, a vertical position is unsuitable. In practice we use a large printing-frame con taining the bromide paper, and clamp it to the board with two adjustable slips, which slide up and down as required. This easel should be fixed at one end of the table devoted to enlarging purposes.
Focussing.—Preliminary focussing is performed with the ruled screen, as in daylight enlarging, and the stop adjusted to produce even definition. A yellow glass cap is then placed on the lens, the negative is inserted, and the final focussing carried out with the bromide paper actually in position on the easel. For exposure simply remove the yellow cap. The rules governing exposure are in general very similar to those laid down for the daylight camera. Do not let the source of light approach too near the con denser until it has been thoroughly warmed, and see that a sharp image of the mantle does not appear focussed as part of the picture on the easel. Shift the burner back wards and forwards until it is quite out of focus. Another caution refers to the yellow glass cap. Sometimes it alters the focus of the lens, and this must be allowed for in the final adjustments. The ideal place for the yellow mask would be behind the negative.
Vignetting.—Suspend a piece of cardboard in which a suitably shaped hole has been cut about midway between lantern and easel ; the nearer the lantern the larger will be the vignette, and the softening of the edges is secured by keeping it constantly in motion. Masks for borders must be pinned immediately in front of the sensitive surface.
Clouds.—These it is preferable to print in before the main picture, giving a very short exposure, probably less than a quarter the usual time, and protecting the site of the landscape with a piece of blotting paper or serrated card. Hold the mask in the hand, shading the sensitive paper at some distance, and move it up and down gently. A very little practice will make perfect in details of this sort. Landscape enlargements look very poor and bare without clouds of some sort, and in river pictures a sug gestion of these clouds ought to be reflected in the water below.
Development.—For the general methods of developing, see the chapter on Bromide Paper. Wet the paper thoroughly before pouring on the developing solution, and, if there is any doubt about exposure, start with a weak developer, such as rodinal r in 8o, which may be strengthened if the image does not come up within a few seconds. Do not be afraid to give full development, and do not remove from developer till a satisfactory amount of vigour and contrast is apparent. Over-development, if not too serious, can be cured by subsequent toning. An under-developed print is of very little value, and quite useless for bromoil, ozobrome, or similar processes.
Enlarged iV egatives. —A positive transparency is first made from the original negative by contact, either on a process or lantern plate or by the carbon method. Develop ment must be carried much further than is the rule for lantern slides ; fair density and plenty of detail is the object to be aimed at, provided that at the same time the shadows are not allowed to get so black that their detail is clogged.
On the whole we think that the best transparencies are made on gaslight emulsions, if only care is taken to give them adequate and even exposure. Even development is also much more important than with the ordinary lantern slide.
The enlarged negative is then made from this trans parency, and whether by daylight or artificial light matters very little. Negatives to answer many purposes are made in bromide paper of thin, vigorous quality. More often a process plate is adopted, with a backing of black stuff to prevent halation. The edges of the transparency should be masked with black paper, so that the light may have no excuse for lateral spreading. Development should be proceeded with very cautiously, for, owing to the larger dimensions of the plate, the shadows are proportionately greater, and convey the impression to the beginner of under exposure.
Personally we prefer the bromide-paper negative for the making of carbon or platinum enlargements. The exposure is not much longer, and the grain of the paper does not show unpleasantly, even if no waxing preparation is applied to increase transparency. Moreover, such negatives are most easily made by contact in a printing-frame with the first bromide enlargement, saving the whole bother of the transparency.
For the further study of the subject we cannot recommend a better work than Mr. C. Welborne Piper's Photographic Enlarging.