It is doubtful whether a photograph can give as much pleasure in any other way as by means of a transparency shown in the lantern. But the transparency, or lantern slide as it is termed, must be good ; and although a good slide is easy to make, yet an experience of many years in judging lantern slide competitions promoted by first-class societies, leads us to believe that the majority of workers do not understand what are the characteristics of the perfect slide. The aim of this article is to show beginners what they must strive after, and to help those who have failed to attain proficiency in this delightful branch of photography.
A lantern slide is simply a print on glass instead of on paper, and the process is akin to the making of bromide prints, using prepared sensitive glass plates instead of the prepared bromide paper. The standard size plate used in the United Kingdom is 3 1/4 X 3 1/4 inches, and consequently, when slides are made by contact - like bromide prints - it is only possible to reproduce a portion of the negative, and therefore, when desirous of including the whole of the picture from negatives which exceed the dimensions of the lantern plate, we must use a reduction process, as we shall show later. Whichever method we employ to make our slide, quite apart from the question of colour, we must ensure that : - (1) The slide shall have a long range of gradation.
(2) There must be no portion of the slide which fails to transmit light.
(3) Only on rare occasions shall there be clear glass on the slide. Characteristics 1 and 2 can be judged by looking through the slide, preferably by setting it at an angle with its lower edge touching a sheet of white paper turned towards a window or a lamp, so that the white light is reflected by the paper through the slide. Under such conditions the slide should look harmonious and free from harshness and without opaque shadows. The slide may then be laid with its surface on the white paper and the high-lights should show a tint of greyness on the image, and only objects of exceptional brilliancy must be rendered as clear glass.
THE LANTERN SLIDE AND ITS CHARACTERISTICS.
While we can make a transparency on an ordinary negative plate, yet this is hardly suitable, because it is so rapid that exposure is a difficult matter. All the plate makers make Lantern Plates of the standard 3 1/4 X 3 1/4 inches, and generally two speeds are issued, one known as " slow " which will give a range of colour from red to black, and another called " rapid," which is more suitable for black tones. We, ourselves, always use one of the " slow " brands, even for reduction purposes, because of the facility they afford for getting warm colours. Still, this is a point of personal feeling and equally good slides can be made from the plates of all the leading makers. As in negative making, we prefer our lantern plates to be " backed," for undoubtedly backed plates ensure finer results, and the extra cost is trifling.
ON LANTERN PLATES.
We will suppose that we have purchased a box of lantern plates and propose to make slides from our negatives. If we use a " slow " brand of plates we may have plenty of light in our dark-room, and a yellow screen such as the Wratten "OO" will be found a boon. Exact distances should be measured off from the source of light to the position occupied by the printing frame and pencil lines made on a shelf or bench, providing either is handy, or even on the wall will answer admirably. It might be advisable to mark positions at 8 1/2 inches, 12 inches, 17 inches and 24 inches, using the 12-inch position as the standard one and rarely placing the frame in any other. Each of these distances doubles the necessary exposure of its predecessor, thus : Distance 8 1/2 inches 12 inches 17 inches 24 inches Relative exposure 30 seconds 60 seconds 2 minutes 4 minutes. Dense negatives will, therefore, be placed nearest the light and very thin ones furthest away.
SLIDES BY CONTACT.
Although an ordinary printing frame will do to make a slide, it is not so convenient as the special frames supplied, because light is apt to creep in at the edges of the lantern plate and slightly fog the margins of the pictures. For those who cannot conveniently procure a special frame we should advise that the ends of their ordinary priming frame are filled up, so that light cannot strike in and affect the edges of the plate. A typical and simple form of the Lantern Slide Printing Frame is that which is suitable for any size negative up to