Of late years, the fashion in cameras for outdoor work has been in the direction of a smaller and smaller plate each season. Once upon a time, whole plate at least was de rigueur, if a man wished to preserve his reputation. Later on, a half-plate became excusable; now we meet Fellows of the Royal Photographic Society unblushingly wielding a little instrument which takes exposures on plates each about two square inches in area. Manufacturers are competing with each other to produce lenses and fittings for these small sizes, just as accurate and highly finished as their larger rivals.
This movement is, of course, partly due to the economy of the small plate, and its portability. A dozen whole plates are a serious burden, as well as an expense not worth incurring when we can enlarge quarter-plate negatives at our leisure. But there is an aesthetic side as well in the matter. Size is an artistic quality of a picture. The man who is content to print every one of his negatives on one particular scale is destitute of the sense of proportion. For some subjects whole plate is ridiculously small; for others it is much too large. Therefore, it is politic to commence with a size which is conveniently manipulated in the enlarging camera, wherein the final dimensions of our exhibition print will be decided.
The process of enlarging negatives is attended with very little difficulty provided the means adopted is an efficient one; makeshift methods are an entire waste of time. The old practice of cutting a hole in the dark-room shutter the size of the plate, and sticking the camera up against it, will not secure the even illumination of the plate which is the first necessity for a successful result. But there are many devices available, by which the ordinary camera may be effectually adapted for use in enlargements without straining the purse strings very heavily.
But before we decide to enlarge a particular negative we must examine its capacity. Unless the focus is fairly sharp we had better leave it alone. When a quarter-plate negative reappears printed as 15 x 12 in., or nearly four times the size, the circles of confusion, instead of being about 1/100 in. in diameter, will be about 1/25 in. Not that the roughened effect will matter greatly with most subjects, considering the greater distance at which they will be viewed when framed on the wall. However, any faults of definition in the original will be horribly exaggerated. The worst cases are those of films which were buckled during exposure in the camera; such are hopeless. No method of enlarging possesses any power to correct erratic focus, although converging lines in architecture may be partially straightened by the use of a swing negative slide, or by inclining the easel upon which the bromide paper is pinned.
Very dense negatives, veiled or stained, are not likely to give satisfactory results; nor will those containing excessive contrast. But in a new negative, made either by direct contact or by transparency, these defects can be mitigated considerably. The best negatives for the purpose are those full of soft gradations and detail, and without any of the harsh contrasts which yield "soot and whitewash" effects.
No great difficulty will be found in devising an arrangement whereby the small quarter-plate or 5 x 4 in. field camera can be attached temporarily to a large camera, the lens of the former entering the front of the latter in such a way that the junction is light-tight. But one of the standard Lancaster or Middlemiss patterns is greatly to be preferred. Enlarging is not worth doing unless under conditions that will ensure accuracy, and an instrument specially constructed for the purpose by a reliable maker is obviously better than the contrivance of the novice; and in the long run not any more expensive. If only an occasional enlargement is wanted, and one particular size will do, e.g. from quarter plate to 10 x 8 in., a fixed-focus enlarging chamber may be constructed, of wood frame and cardboard, to work with the ordinary quarter-plate camera. For dimensions see table of enlarging distances.
In practice, daylight enlarging is fairly simple. The negative is fixed in position at A and focussed to the required size on the ground glass at B. The ground glass will afterwards give place to a dark slide containing the bromide paper. We need hardly remind the operator that the larger the size of picture required, the longer the distance must be between B and C, and the shorter the distance between C and A; in fact, from B to C will equal A to C multiplied by the number of times the enlargement is to exceed the original. A negative is not a handy thing to focus, as it provides no clear standard of comparison; and in getting accurate focus it is usual to substitute a glass plate ruled in parallel lines and squares. Focus with a full aperture and then stop down, remembering that enlarging work is a very severe test of the virtues of a lens, and that the smaller the stops the better for the outlines, but, on the other hand, the longer the exposure.
When using films or plates of smaller size than the full capacity of the negative holder, take care that the margins are well masked, either by the suitable plate-carriers or black paper. Marginal light is as fatal almost to good enlarging as pinholes in the bellows.
Choose a window having a north aspect or, at any rate, such that the direct rays of the sun are not within the field of view; tilt the camera as shown in the figure in order to secure even illumination, which is not interfered with by the shadow of the earth, intrusive trees, buildings, etc. If the situation is very confined, take it on the roof or out-of-doors and tilt nearly upright.