The Optical Magic Lantern Journal (January 1890)

13 The Optical Magic Lantern Journal and Photographic Enlarger. 61 qualities of two pictures can be better ascertained when they-are placed side by side, two lanterns are used for projection, their lizhting and optical properties being similar. All those slides made from the same negative are disposed of before those from another are introduced. At the outset we have two transparencies projected ‘side by side ; it is to be determined which of the two is the better. This, then, is decided by general vote, such as “the right” or “the left.’ Supposing that it has been determined that that on the “right” is the better, the slide on the ‘‘left” is removed and laid to one side, and its place supplied by another, which is then voted for, that which is deemed the better remaining in the screen. In this way all the slides are disposed of, and that remaining last upon the screen will be that which, according to vote, will have: been decided to be the best of the series. Sometimes it is even advantageous to transpose the two pictures shown, when there is any difficulty in deciding the better. When several slides of the same subject are thus exhibited in succession, it is not an infrequent occurrence for those who made the slides not to recognise their own when on the screen. Lantern Slides and Lantern Slide Making. WITHIN the past two years a greater amount of interest has been shown in lantern slides and Jantern slide making than ever before, partly on account of the better and more uniform quality of plates supplied and the simplicity of the development processes which have come into use. The use of the wet plate process and the collodio~ bromide process is so limited, that neither can be ; regarded as a factor of importance at the present time. | But it may be said in their favour that, while their | rapidity is much less, they are less expensive than the | dry plate. The process is, therefore, well adapted for the manufacture of lantern slides by the quantity ; but it is doubtful whether the delicate half tones can be brought out as beautifully as with the improved dry plate. One peculiar advantage of the wet process is the remarkable clearness of the high lights so easily obtained. However, it is a variable process, requires more attention, time, and care than the average amateur has to spare, and involves a certain disagreeable soiling of the hands and clothes. which is unpleasant. It is a great saving of time and labour to use plates already cleaned and repaired, as is now the case ; which accounts for the ease and certainty with which lantern slides may be made. After a little practice the technical difficulties are easily mastered ; then the making of a slide becomes a pleasure and more certain in its results than is usually the case in the making of silver print, besides possessing a delicacy of detail that it is nearly impossible to see on paper. One of the chief requirements of a negative for slide making is that it shall be very sharp and distinct, with sufficient density in the high lights to prevent the clouding of the sky portion of the slide. A moderately dense negative, therefore, generally produces a crisp slide, since it enlarges the limits of expo| sure, and allows more latitude in development. It does not follow, however, that an excellent slide may not be made from a very thin, clear negative. It can be done by careful timing and a proper developer. A fogsy negative will produce an unsatisfactory slide. Thus much depends on the negative ; in selecting such for slide work from a summer's collection, reserve only those that are sharp and of good average density. There are two different ways of making slides. One is called the contact method, and the other reduction by the camera. In the contact method a portion ofa large negative is sometimes selected, on which the sensitive plate is laid in contact, film side next to the negative film, in a printing frame. Over the back of the sensitive plate should be placed a sheet of black or orange-coloured paper, to prevent the reflection of actinic rays from the back of the sensitive plate against the under side of the sensitive film. The plate is then clamped in contact with the negative by the usual springs attached to the printing-frame back. (7o be continued ) 20: AN attachment for supporting the fronts of optical lanterns has been invented by Mr. J. H. Steward, London. By means of racks the fronts may be raised or lowered ina manner that ensures perfect registration of the discs. The ial accompanying cut will show at a glance the generai arrangements of this invention.