The Optical Magic Lantern Journal (July 1893)

100 The Optical Magic Lantern Journal and Photographic Enlarger. We have received one of the cheaper grades, the working of which is as follows :—Twelve quarter plates are placed in sheaths, which are then inserted in grooves in the camera by opening a lid or door at the top. The grooves extend only about an inch down the plate, and when the reservoir is racked forward the foremost plate trips over a spring, which causes it to drop out of the grooves mentioned. This plate is made to fall face down by tipping the front of the camera downwards, which causes the plate to fall on the inclined base shown in cut, when a tip of the instrument in the opposite direction causes the exposed plate tc slide into a receptacle under the unexposed plates. With the camera first sent to us we found the placing of the plate at the focal plane was largely a matter of chance, but since calling the attention of the makers to this, they now fit each camera with means for ascertaining this by a notched wheel and pointer. The achromatic lens 1s provided with a shutter (time or instantaneous), which is always set, and which is operated by cords. Two finders and a level are provided, and also a small dial figured from 1 to 12 upon which the number of plates exposed can be registered by pushing the index forward each time an exposure is made. —:0: —— On the Preparation of Lantern Screens. By Hy. Wuirs. Persars nothing is more important in securing a brilliant effect in a lantern exhibition than the quality of the surface on which the picture is projected, and the ordinary sheet falls far short of perfection in this respect. If we desire the finest and most perfect rendering of the slides, it is of the utmost consequence that the preparation of the screen should be most scrupulously attended to, and, moreover, when made, carefully protected from injury. A screen will either improve or mar the skill of the best lanternist who may be working with the most unexceptionable apparatus and light to be procured. It is therefore an absolute necessity for the best results to have the screen as white, solid, smooth, and free from defects as possible. Many screens are quite inadequate to show up the delicate qualities of a perfect slide even with a brilliant light, consisting as they do of } merely a white (sic) calico sheet attached to a frame, which, more often than not, in addition to its bad colour, is embellished with creases, joins, and I may add dirty marks, having anything but an artistic effect, especially where each defects show in the skies and lighter portions of the projected picture. The acme of perfection in a lantern screen is, that it shall possess a fair smooth surface, unbroken by any seams, stains, or defects whatever, and be of an absolutely dead opaque white when seen by artificial light. As all oil lights are more or less tinged with yellow, and that yellowness is communicated to the screen, to the detriment of the picture, its surface should be of a tint calculated to neutralise the yellowness and make it appear of a pure white. To any observant person the term white is but a comparative expression, and very few whites so-called are absolutely colourless, this is easily proved in a simple manner by laying a number of pieces of so-colled white paper of different makes in juxtaposition, when their different shades of colour will be very apparent. Anyone of them alone would be termed white, although they are really variations of blues, pinks, and yellows. It has been customary for years to add a little blue to white in order to neutralise this objectionable tint and produce the effect of a purer white, a familiar instance is the ordinary white-wash which almost invariably has a little blue added to it for it has been found that a faint blue has a more fresh and clean appearance than natural yellow tinge of whiting. Albumenized papers are tinted with the same idea, any yellowness being less perceptible in the tinted paper than in the plain untinted. So in the preparation of the lantern screen the white should have a distinct tinge of blue by daylight which will be found to produce purer lights in the pictures thrown upon it than any other tint, and in this respect be as near perfection as we are ever likely to get. Next to colour opacity has to be taken into consideration, a surface that will reflect most of the light in the same condition in which it is received without any perceptible degradation of tint, is the kind for our lantern screens possessing which are calculated to give thorough satisfaction to the most exacting critic. In a retrospective view of the lantern shows we have seen how few slides have been really shown to the best advantage from little else than the imperfect surface on which they were projected. We are so accustomed to see make shifts and imperfect backgrounds that we perhaps note the defect in a perfunctory sort of fashion and think we make a sufficient mental allowance for it, as a thing that could not be