A postcard lantern or its equivalent, for a simple substitute is quite easily devised, will often prove of use to the photographer for special work. It may be of great assistance, for example, when one desires to make a copy or an enlarged negative from a print, while at the same time introducing modifications, or blocking out unwanted portions.
Direct enlarging with a postcard lantern is not new, having in fact been suggested by A. E. Swoyer, in the "American Annual of Photography" for 1914. That writer, however, regarded the projected image as an end, whereas in the present article it is simply a means to an end or intermediate stage, while the method adopted is entirely distinct.
It will be seen, by reference to fig. 1, that the postcard lantern consists of a body, A, in the front of which is fitted the objective, B, while at the back is a hinged door, C, with grooves to hold the print, or sometimes a sliding carrier. A good source of illumination is two 30 c. p. or SO c. p. metal filament bulbs, D and E. The inside of the body U whitened, and it will be noted that the ides nearest the lamps are at such an angle as to reflect the light on the print. Two small interposed screens, or some similar arrangement, prevent direct rays reaching the lens. Cowled chimneys are usually fitted over the lamps, and due provision made for ventilation.
The most important item is the lens, which should be of fairly large aperture, owing to the loss of light by reflection, and should have a flat field. Cheap postcard lanterns often have objectives with so round a field that the holder has to be curved to get uniform definition. Such a lens is, of course, quite unsuitable for copying or enlarging. Many of these objectives are not even achromatic, and, on the whole, a proper photographic lens is Bach to be preferred, even to the best of them. The lens must be capable of covering a plate at least as large as the print to be projected and the lantern should have sufficient focal adjustment or extension to render a fairly small picture possible when required.
There will be needed, in addition to the lantern, an easel of the type shown in fig. 2. This consists of a frame, A, containing a
wheat of plain glaze, B, and supported in a vertical position by a firm base and struts. To the frame A, is hinged a smaller frame, C, which, when closed and secured by a turn button, presses on the glass.
The print to be copied is inserted at the back of the lantern, and focused sharply to the desired size, on a sheet of tracing paper stretched taut between the two frames on the easel; or, if preferred, a piece of finely ground glass may be placed in the frame, A, instead of a plain piece, and the tracing paper dispensed with. If the second coarse is adopted, the ground aids) of the glass should be at the back of the easel.
The worker, standing or sitting behind the easel, now has it is power to modify the projected image considerably, by of pencil or stomp work on the ground glass or tracing and even the brash may be employed advantageously in cases. Since the image is a positive, there is no difficulty in exactly how the final result will appear. Cars, of course, have to be taken that the work matches the colour of the image.
The next step is to make a negative from the modified image, by setting up a camera, F (fig. 1), behind, and central to the easel, O, without moving or interfering with the lantern. Thus, the copy negative will contain all the introduced work as well as the essential characteristics of the original, and the result if all is well done, will be a considerable improvement. The negative may obviously be any required size, though preferably it should be smaller than the projected image, as this reduces the likelihood of grain showing.
It will be seen that this method affords a handy way of inserting a black background, by painting round the projected image with any suitable opaque; or of introducing accessories on an originally plain tight background; copying joined up prints an I combinations; adding skies to landscapes; and many other purposes.
One may also make enlarged modified negatives direct from prints, by working-op the projected image, as before described and then, having find covered the objective, placing a large plate in the frame behind the grand glass or tracing paper, the exposure being then given by uncovering the objective for an estimated time. In this case, the postcard lantern must evidently be light-trapped properly, which is not so necessary for copying with a camera; while a little extra space mast be left in the rebate of the easel frame to allow the insertion of the plate. Enlarging in this way softens the definition a little, and thus lends itself to artistic elects. There may also be an alight grain, bat with proper cars this should not be objectionable. Backed plates should invariably be used.
Since metal-filament lamps do not give out much heat, it in traits feasible, with an intelligent study of size and ventilation, to hint a simple wooden, lantern of the kind under discussion; or, with but a little adaptation, one or other of the various contrivances for ^Urging by reflected light without a condenser may be pressed into service.
To anticipate difficulties which may, perhaps, perplex some who are unfamiliar with postcard lanterns, it should be stated that the projected image is always laterally reversed. Viewed from the rear of the easel, however, there is no inversion, when explains why copying is done from the back, that also I fortunately the most convenient position.