The Optical Magic Lantern Journal (May 1896)

The Optical Magic Lantern Journal and Photographic Enlarger. 87 print from it, and then to print a3} inch square from some part of it on a lantern plate. Now let us see to what this leads. First, in any case, to a square picture, a shape that a painter rarely, if ever, adorts. Probably when this square picture measuring 2{ or 3 inches each way is put in the lantern, it is found that the corners are not illuminated, for the ordinary 4 inch condensers are not large enough to illuminate a square of this size. Hence, a circular, or at any rate a cushion-shaped mask is used. The former shape is rarely suitable to a picture; the latter is most objectionable. It is, L believe, one that never will be found in any exhibition of paintings, and very rarely in any exhibition of photographic prints. But this is not all; if the lantern plate is put nearer to one end of the negative than the other, the perspective suffers, for the point of sight to which all parallel lines at right angles to the plane of the picture converge, is, if the camera has been rightly used, equally distant from each end of the negative ; but if the lantern plate is not placed centrally on the negative, the point of sight will be thrown either to the right or left hand side of the transparency, the result of which, in some cases, would be most unpleasant _to any educated eye when the picture is thrown on the screen. But even if the lantern plate is correctly placed, the composition of the picture must suffer from the loss of half an inch from cither end of the subject included in_ the negative, if it was originally composed with a view to a 4 by 3 inch print. I think if the possessor of a quarter-plate camera wishes to make his slides by contact, the best thing he can do is to cut for each back he has, two slips of wood +8 inch wide, 3} inches long, and of such a thickness as will lie in the double dark back when closed. If one of these is placed at either end of the back, it will leave a space of 33 by 22 inches between them for the insertion of a plate. This size is exactly one quarter of a half-plate, and, of course, of the same shape—a shape which I believe is the ideal one for a picture, although the subject will often compel some deviation from it. The cheapest way of getting plates of this size will be to invest in a glazier’s diamond, and cut up half-plates into four equal parts. The cost of the diamond will soon be saved, as the cost for a dozen negative plates will only be 63d., instead of ls., as it would be if quarter-plates were used. When the plates are inserted in the backs, in the manner recommended, we shall get a vertical view with the reversing back of the camera arranged as if for a horizontal view if a quarter-plate were being used, and vice versa. This must, of course, be remembered, and, indeed, cannot be forgotten if, as is most desirable, the ground glass has two strips of black paper, 42 inch wide, pasted along each end, thus leaving a space of exactly the same size, and taking in exactly the same amount of subject as will be depicted on the plate when the exposure is made. By this means the picture can be easily composed on the screen. (To be continued.) ———'0: Topical Notes. By Tue DrEaMEn. Lanrern evenings at our Society meeting have ‘been somewhat at a discount lately, Rontgen ray experiments, or rather demonstrations, having to a certain extent taken their place. THERE are some very fine Réntgen slides on the market now, aud one or two included in a lantern entertainment would, no doubt, be interesting, but the well-known hand shadowgraph should be avoided. Snakes, mice, and birds are a little more uncommon. A coop method of making diagram slides is to use celluloid with a finely-ground surface, and make the drawing with a fine pen. In this way several different coloured inks can be used, which is often exceedingly useful. Besides, the drawing can be removed when done with, and the sheet of celluloid used again for another diagram. A LANTERN does not deteriorate so much when in use as during the period of its non-use. When about to be placed away for a time the lenses should be gently dusted with a camel hair brush, the condenser removed from its cell and washed. All metal and wood parts should then be thoroughly cleaned and dusted, and, finally, wiped with an oily rag allover. The oil will form an excellent protective coating. Jets, saturators, dissolvers, regulators, and pressure gauges (no oil in the working parts of the last two, mind) should be examined and cleaned; then slides should be gone over and put in order. No doubt a few will require new cover glasses, some new slides will have to be made to replace broken or damaged ones, some will require fresh binding strips, and ail will want a polish with a glass cloth.