The Optical Magic Lantern Journal (March 1900)

The Optical Magic Lantern Journal and Photographic Enlarger. 31 quickly from black through all shades of warmth to red. The high lights are not stained or otherwise coloured by the process, and the operation is arrested at any: desired stage merely by washing in water. The tones are more pleasing than those obtained -with uranium, and there is every reason to believe that they are permanent. The materials, it may be added, are very inexpensive. & Bd a For Polishing Cover Glasses.—There is, says Mr. F. W. Cooper, in the Photogram, nothing better than a piece of chamois leather or velveteen stretched over a board (2 feet by 5 inches by 2 inch) and tacked to the under side, a piece of stout twill being interposed between the board and the velvet. The glasses having been cleaned and merely drained, can ba very quickly and perfectly polished by rubbing up and down the leather or velvet surface. The board has the advantage of obviating any risk of cutting the hands or breaking the glasses as when polishing is done with a duster and the glass held in the hand. oe ed Baad A Hint for Lanternists.—The addition of camphor to the oil has often been recommended as giving increased brilliancy and whiteness to the light. Monsieur G. de la Turetiére has, however, recently recommended acetate of amyl in place of it. Amyl acetate is an extremely inflammable liquid—though not dangerously so—and burns with a brilliant flame. The proportions suggested are 1 part of the acetate to 4 parts of oil. It may be added that the odour of amyl] acetate when diffused in the air is very agreeable, resembling essence of jargonelle pear, and serves to disguise the often unpleasant smell noticeable when an oil lamp is being used. cd oe bod An. Opaque Screen.— M. Molteni, in Helios, gives the following instructions for making an opaque screen. Prepare a mixture of gum arabic (1 part), powered magnesia (4 parts), and water 80 parts. In this, soak your cotton or linen sheet. On drying it has a matt and very reflecting surface. In place of magnesia, whiting can be used. If the screen is to be a fixture, all that is necessary is to stretch it on a wooden frame. [If it is to be rolled, the upper edge must be nailed to a stout roller, and the lower to a heavy curtain rod. The mixture for the roller screen should contain a little glycerine to give the fabric the necessary suppleness and to prevent the pigment scaling off when the screen is rolled and unrolled. Wanted a Camera. By T. PERKINS. AMERA makers seem to spend all their ingenuity in inventing some new form of'‘hand camera, of which class there is an abundance, if not superabundance, on the market already, while there is a form of camera which certainly I have never met with or seen advertised in any dealer’s list which would be an inestimable boon to many photographers, and which ought, if it were put on the market at a reasonable price, to have a very large sale. I mean a stand camera with all the movements—rising front, swing back, etc., to which we are accustomed in modern stand cameras, but of a small size ; one in fact that would take plates a quarter of the size of a half-plate, or 34 by 2§ inches. The primary use of sucha camera would be the production of negatives from which lantern slides could be made by contact. The making of slides by contact has several advantages over the process of making them by reduction. The most evident advantage is that they can be made by artificial light, and thus many photographers, whose days are fully occupied by other matters, and whose evenings only are free, can make lantern slides in the winter. Again, it is well-known to anyone who has made many slides, that by varying the intensity of the light very different results may be obtained; or to put ; the matter in another way, by varying the intensity of the light good slides may be made from negatives of very different characters. A bright clear slide may be obtained from a thin or forgy negative by reducing the light, and a soft slide from a hard negative by increasing it. When a slide is made by contact it is easy to increase or diminish the light to almost any extent by varying the distance of the printing frame from the gas burner or paraffin lamp; whereas when a slide is made by reduction, although by stopping down the copying lens the light may be reduced, it is impossible to increase it beyond a certain limit determined by the largest aperture that the lens has. If the lens is one provided with a stop of {, and sufficient sharpness can be got when this stop is used, it must be remembered that there is a considerable increase in the working focal length of the lens owing to the fact that the negative is brought somewhat close to it, and the lantern plate much beyond the principal focus, so that