The Optical Lantern and Cinematograph Journal (Nov 1904-Oct 1905)

THE OPTICAL LANTERN AND CINEMATOGRAPH JOURNAL. 3i ON PHOTOGRAPHING WITH A VIEW TO THE PRODUCTION OF LANTERN SLIDES. By Professor Golding. ONE of the most useful branches of Photography, as well as one of the most popular, is the production of Lantern Slides, which enable their possessor to show the results of his labours to a large number of spectators, either in the privacy of a friendly gathering, or to a large public audience, by whom their merits may be better appreciated than can be the case when pictures on a small scale are presented for the inspection of one person at a time. The preparation of such slides affords a pleasant and useful pastime to the amateur photographer, and gives wide scope for the exercise of his skill in manipulation, for it must be remembered that when an object not more than three inches in diameter is magnified sufficiently to cover a surface of many feet, every small blemish, which would scarcely be noticed in the original, becomes enormously exaggerated, probably to a degree which causes it to be forced upon the eye of the spectator as a most obtrusive object. A line so thin and delicate as to elude observation altogether becomes on the screen a bar or a cord of considerable width and coarseness, and a surface which appeared to the eye perfectly smooth and uniform, is depicted as an exceedingly coarse and rugged one, whose irregularities resemble hills and valleys rather than anything else. On the other hand, delicate detail and beauties which failed to impress the eye in the original, become revealed, and once more the thing of beauty becomes a joy, if not for ever, at least sufficiently long to impress itself on the memory of the beholder for many a day to come. While any really good photographic negative may be reproduced as a lantern slide, the worker in this direction will soon discover that some ixe far better suited for the purpose than others, and that if the best results are to be obtained, the purpose for which it is intended should be kept in mind in the selection of the subject and in the treatment it is to receive, as well as in each step of the process of exposure, development, printing, toning, and every detail until the slide is completed and ready to be placed in the lantern. The shape and size of the negative, as well as its qualities of density, range of tone, angle of view included, contrast of light and shadow, and every other detail, must be taken into consideration. One thing is essential — the negative must be very sharply focussed. It is not necessary, or even desirable, that it should be hard or harsh, but every detail must be perfectly distinct, otherwise, when magnified, the picture will appear blurred to an extent which will render it quite unfit for presentation. A degree of softness which involves indistinctness or want of definition, wherever it may be admissible, is quite out of place here, and the lens to be used must be one which will bear the test and give an image equally sharp from centre to margin, if the resulting negative is to be suitable for its purpose. Indeed, there is often an advantage in using a lens capable of covering a larger plate than the one employed, in order that this uniformity of definition may be secured by the use of the central part of the lens only, without the necessity of employing an inconveniently small stop, and so unduly lengthening the exposure.