In making usual exposures the exposing crank is turned steadily and with skilled uni formity 120 times a minute, each turn of the crank making eight exposures on the film. The exposed film is removed from the camera in the dark room and wound upon a *pin frame? This is a square frame, generally of brass, with diagonal and semi-diagonal spokes radiating from the centre, each.studded with pins slightly longer than the width of the film. Starting at the centre of the frame the film is wound around and around in an ever-widening spiral which offers free play between the coils for the developer. Before compounding the developer a test is made upon a few inches of film clipped from one end, and according to this test the developer is prepared with such developing agents as promise the best results. The develop ing agents usually employed are metol and hydroquinone in combination. Glycin and eikonogen are also used. The pin frames with their coils of film are immersed edgewise in an upright bath. The development aimed at is one that will give the widest contrast of highest light and deepest shadow, with a full range of intermediate values in soft gradations. Hydro quinone is depended on to give the first quality and metol the second. When thoroughly fixed and washed the negative is wound upon a large revolving drum to dry.
The positive film used in the exhibiting lan tern is made from the negative by a photo graphic printing process. This positive film is perforated exactly like the negative film, but is coated with a much slower emulsion and con tains a larger proportion of silver chloride salts, so that the development of the positive produces blacks of greater opacity, yielding pictures of more contrast and brilliancy. The negative and the unexposed positive film are placed face to face, the perforations matching, in the printing camera and are pulled down ward together by the hook mechanism through a gate, in front of which is an artificial light, commonly an incandescent electric lamp. A re volving shutter at the gate cuts out the light while the film is being moved and makes the exposure while it is stationary, at the rate of from five to eight exposures per second; and this is kept up until the negative film has all been printed. Another reel of positive film may then be attached and another printing made— and so on for as many positives of that sub ject as are required. It is to be noted in pass ing that no two negatives can be relied on to require exactly the same amount of light in printing. Skilled judgment must determine the speed and opening of the shutter which will produce the best results.
The development of the positive film is con ducted in exactly the same fashion as with the negative film, but the light used is much stronger. An orange light is perfectly safe
with a positive film. The progress of the de velopment is closely watched by examination before the light, and the process is stopped when the necessary density is obtained—a mat ter to be determined by the trained judgment of the operator. The film is then rinsed, fixed and hardened and washed absolutely free of hypo before drying. There may- be, if desired, further treatment by tinting or toning to pro duce certain scenic effects. In tinting the whole film is passed bodily through a bath of some dye which imparts its color to the gelatine pellicle, but does not alter the black of the silver deposit. For example, a blue hue is given for a moonlight effect, pink for sunrise; yellow brown for lamplight; red for firelight, etc. In toning the silver deposit itself is chemically changed in color, the clear part of the film re maining unchanged. Some beautiful effects in sepia, green, indigo, etc., are thus produced.
The greater part of the films produced and exhibited at the present time are those which Along with a large number of comic and delineate what might be called picture-stones. farcical subjects there are pretentious panto mimic plays — of the type known as *photo plays* (q.v.). Some of these have engaged the talents of actors and actresses in the front rank of their profession. In addition to these pre sentations of theatrical proportions, vast im aginative and historical pageantries have been *staged' out of doors, with thousands of per formers and a wealth of artificial scenic acces sories running in value to many thousands of dollars — all to produce the one master nega tive. In not a few cases whole companies of performers have been transported to some far distant locality in order to secure the appro• priate local color" for the film-play. The moving-picture mechanism lends itself readily to an endless variety of trick pictures, through the facility with which a film may be cut and joined to another set of pictures, showing no break on the screen. For example, a magician may be seen to touch the with his wand, and instantly he becomes a mammoth wriggling caterpillar—through the simple join ing of the two distinct films. As films may be run backward as well as forward the most re markable extravaganzas may be produced. A wall may be seen to build itself from a pile of bricks — the picture actually taken having been the demolition of the wall. A picture of a man climbing down a fire-escape rope may be shown on the screen as one climbing up the rope.