R. G. HARRIS

In the previous chapter a very elementary de-cription was given of the production of a lantern slide with the aid of a printing frame. The method given would scarcely satisfy any but a beginner anxious to produce a lantern slide without venturing too far into the intricacies of the subject. Complications and refinements are sure to attract the worker before long, the printing frame will be discarded for the camera, and the black colors gradually give way to warmer ones. To anticipate the desires of the worker, it will be desirable to devote the present chapter to the description of some arrangement for produc-ing lantern slides by reduction with a camera, involving the use of both artificial light and day-light.

It was remarked earlier in these chapters that for any negative larger than quarter-plate it was essential to resort to camera reduction for producing lantern slides if the whole of the subject was wanted in the slide. The opinion may also be hazarded that as the lantern slide worker becomes more competent he will incline more and more towards camera work as a means of slide making. Some processes for making lantern slides, though giving most excellent results, are too slow to permit of exposures in the camera, and one is compelled to reserve them exclusively for contact use, but in case of a plate like the lantern plate of commerce, which is available either for contact or reduction, the camera will be found to be the most satisfactory means of obtaining a lantern slide. Even in the case of quarter-plates, which have been taken with a lens of fairly long focus, it is seldom that the slide would not have been better for the inclusion of the whole of the subject.

The camera for use in making slides by reduction may be the ordinary field camera if it is of the "stand" camera pattern, but where lantern slide work is followed systematically it is most desirable to have a camera relagated to the work of lantern-slide production. The arrangement which is used by the writer is simple in construction, and does all that is required in making lantern slides by daylight reduction. It consists of a baseboard about four ft. long and one ft. wide ; between two parallel guides running the whole length of this baseboard slides a block of wood the same size as the base of the camera, and having a ledge at either end to hold the camera firmly. A negative holder, with carriers for various sizes of negatives, slides at the other end of the baseboard, and the whole enables lantern slides to be obtained from negatives 15" x 12" down to 4 1/4| x 3 1/4. The camera used on the baseboard is a square half plate, but, of course, any camera can be adjusted for use in a similar manner. A very convenient instrument is one of the square sliding-body cameras made for wet plate work, which might be bought for a small sum. If a camera of this description is firmly affixed to the block sliding between the parallel guides, it makes a most efficient camera for lantern slide reduction*

The lens should not be of very long focus, or the exposures will be inconveniently protracted. Four and a half inches is a convenient focal length, and although a single landscape lens is permissible, it is better to use a lens of rapid rectilinear form to avoid any possibility of distortion. The whole arrangement is inclined so as to command a clear view of the sky. If it is possible to exercise any choice, a northern aspect should be selected, as then no trouble is experienced from sunlight striking the negative. Should a north or northeastern aspect be unobtainable, or should such objects as trees and chimneys project into the field of view, it is convenient to cover that part of the window used with one or two thicknesses of tissue paper, or, which is even better, a single thickness of white demy paper. Two rods are used connecting the camera and negative holder; these are simply loose rods laid across to bear the focussing cloth, which is thrown over previous to exposure, to make a dark chamber between the lens and negative, a precaution that prevents any diffused light operating on the negative from the rear. Using the arrangement for daylight exposures, with a four and a half inch lens and 1/16" stop, the exposures with ordinary lantern plates will be about twenty seconds for black colors and up to three minutes for warm colors, the negative reduced being a half plate, and the light outside good, diffused spring light.

It will be impossible here to go into the question of conjugate foci, so intimately associated with all matters of enlarging and reduction. The better plan for the beginner is to arrive at the correct distances that are necessary between the lens and plate on the one hand, and between the lens and negative on the other, by a system of trial and error, remembering that the greater the reduction the further the negative has to be from the lens, and the less camera extension needed. Once the correct distances have been found, marks made on the baseboard for the positions of the camera and negative holder will enable them to be speedily adjusted on all subsequent occasions. As a rough guide for preliminary trials, the accompying table may be of assistance to the beginner.

Reduction in the camera by the aid of artificial light is quite easily accomplished in the absence of daylight, and the majority of lantern slide workers will find artificial light more convenient, as work can be carried on in the evening. The apparatus is that used in daylight reduction so far as the baseboard and camera are concerned, but is is, for convenience sake, used horozontally upon a work bench. Two Welsbach burners constitute the source of illumination, and the light is diffused by passing through two thicknesses of tracing paper placed over the negative holder. The burners require adjusting at a sufficient distance from the tracing paper to give even illumination, and to this end they are fixed on a sliding stand.

Focus of lens

Half-plate Negative to 3 1/4 x 3 1/4

3 1/2 inches..........................

14 inches negative to lens

4 1/2 in. focussing screen to lens

4 1/2 inches.........................

18 in. negative from lens 6 in. screen from lens

5 inches ...............................

20 in. negative from lens 6 1/2 in. screen from lens

6 inches...............................

24 in. negative from lens 8 in. screen from lens

The lens for use with artificial light should have as short a focus as possible to secure the maximum amount of illumination. A 3 1/3" rectilinear is very convenient if of good quality, so as not to require stopping down before definition can be obtained. In place of the Welsbach burners an arrangement may be substituted by burning magnesium ribbon, or a flash lamp. The burners, however, are by far the most reliable il-luminant. Magnesium ribbon is most convenient for contact exposures with very slow plates, but for reducing purposes its use is attended with some degree of uncertainty.

The simplest way of camera reduction, when the negatives are all of one size, is to use a "fixed focus" camera. A rectangular box of the size of the negative to be reduced has provision made for holding the negative at one end. At the opposite end of the box is a frame with 3 " x 4" aperture, into which a lantern plate is placed and held in position by a spring, a light tight lid fitting on the end of the box. The lens is fixed near the middle of the box in a rigid frame, in the position to focus accurately upon the lantern plate. All that is necessary is to place the negative in position at one end of the box and a lantern plate at the other, to cover up both ends until the apparatus has been illuminated, and then to expose by removing the cover of the negative.

It will be seen that this method of work has very serious limitations. Should it be necessary to enlarge slightly the image so as to exclude from reproduction some unessential portion the camera fails utterly. Nor is it possible to use it for any other size than for which it has been made. Printing by "contact" necessitates little apparatus beyond the ordinary printing frame as used for paper prints. Ingenuity has been expended in devising printing frames specially for use in lantern slide work. They are convenient when a slide is printed by contact from some portion of a negative very much larger than the lantern plate. But the slide maker may be contented with an ordinary printing frame, merely putting underneath the negative a piece of plain glass the size of the frame for the negative to rest upon. By so doing, no danger of fracturing the negative from the unequal pressure of the lantern plate may be feared.

Whole Plate (8 1/2x6 1/2 to 31/4x3 1/4 21 inches negative from lens

4

"

screen

"

"

27

"

negative

"

"

5 1/2

"

screen

"

"

30

"

negative

"

"

6

"

screen

"

"

36

"

negative

"

"

7

"

screen

"

"