Stop Motion Work
( Originally Published 1924 )
THERE are two variations in speed in motion picture work which greatly enlarge the scope of cinematography. These two variations are known as "Slow-motion" and "Stop-motion." The great similarity in the two terms leads to great confusion.
Slow-motion, or as it was originally called "Motion Analysis," is made by exposing the film at great speed, from five to thirty times as fast as normal. This results in a picture which when projected, slows down all motion to such an extent that a man leaping into the air rises as though buoyant, and sinks to the ground as lightly as a feather. Examples of this work are fairly common in news and review work, but so little taste has been exercised in selecting subjects that these pictures now pall, unless of exceptional interest.
The great speed with which the film moves through the camera is so hard on both the film stock and the intermittent mechanism, that unless a special intermittent is used, both film and camera are endangered. Owing to this fact, this work is not practical for the amateur, but the opposite effect, or stop motion is very easy and is capable of rendering very fascinating effects.
Stop-motion is not, as might be thought, a rapid rendition of the picture, but is a process whereby dolls and other inanimate objects exhibit action. Cartoon work, although beyond the power of the usual amateur, is based on stop-motion work.
The simplest example will be doll work. The set is first constructed, its size being regulated by the size of the dolls used. Do not try to imitate reality in the set. An extremely simple or extremely fantastic set is best, as the obvious artificiality of the set helps the effect greatly.
Now dress your dolls in the costumes which are to be used. Set them in position for the opening scene, and focus the camera. Insert the crank in the single crank opening, and when all is ready expose a single frame. After a short interval, expose another frame, and do this until six frames have been exposed. Develop this film to see if the exposure is correct. It will be noticed that in this work the exposure can be made any reasonable length, even up to one second, so that indoor work is practical even when using lights of comparatively low intensity.
Experiment until the proper exposure is obtained. This should be done in two or three trials. After this primary experimentation, no more such work should be necessary. If the various constants, such as distance, lighting and so forth are maintained the results will remain constant.
Now, begin again. Expose a single frame. Then move the arms or legs of the dolls a very little, and expose another frame. Repeat this process through the entire action. A step should occupy from one-half to one second. Divide the entire motion into eight to sixteen parts and move the limb through this part at each exposure.
Care must be taken that all action is carried on. That is, Number One will take a step while Number Two starts to raise an arm, both of these must be carried on at the same time. In this work the exposure will take about one second, and the inter-exposure arrangements will occupy about fifteen seconds at first. This means four frames to the minute, or two hundred and forty frames an hour. These two hundred and forty frames will occupy fifteen feet of film, and will have a screen time of fifteen seconds. A ten minute run is about the minimum run for an interesting play-let, so this will require some forty hours of hard work. True, it takes effort, but the result repays you. This is the method employed in making cartoons, but in that work, the cartoon must first be drawn, and each successive drawing must be an exact duplicate of the preceding except for the moving parts. By the use of transparent sheets and other devices, this cartoon work is somewhat simplified, but a detailed explanation of cartoon work would fill a volume in itself.
A very interesting variation of stop-motion work is used in scientific work. A plant is placed within a screen which protects it from air currents, and an exposure is made at intervals of a half minute, five minutes, fifteen minutes, or whatever it must be. This interval is determined by a calculation of the length of film to be used and the duration of the total time which will expire. By this method a plant can be made to thrust up the ground, grow, bud and blossom before our eyes in five or ten minutes.
Many variations of this work will occur to the amateur, and if an exceptionally good or unusually interesting strip of stop-motion film is obtained, if standard gauge, it can be sold at a price considerably higher than that paid for ordinary news work.