Amazing articles on just about every subject...


Motion Picture Camera In Use

( Originally Published 1924 )



THE first thing to do after purchasing the camera is to master the cranking. It appears to be very simple to set up the camera and turn a crank. The professional cinematographer seems to watch everything else around him but his crank, and so he does! He has cranked so many thousand turns that it is second nature to him to crank steadily and uniformly at proper speed, that even under the stress of the utmost excitement, when he is hardly able to control himself otherwise, his hand will continue the same steady grind, but it takes many weary hours of conscientious practice to acquire this facility.

A careful consideration of the laws underlying the mechanical portion of the science of cinematography will help the amateur to understand the great importance of correct cranking. It is really so important that unless it is mastered, success of any degree in cinematography will be impossible!

In normal motion film, sixteen frames are exposed each second, each being a photograph of the action taking place during an interval of one thirty-second of a second or less, but whatever the interval may be it is the same in each frame. It is also well known, universally known among amateurs, that the duration of the exposure is the vital factor in the determination of exposure, and that an exposure greater or less than normal will mean an incorrect exposure.

Probably the best course to pursue is to consider each error by itself, and the sum of don'ts will clearly indicate the necessary "do's". First let us consider the effect of slow cranking, and in order to illustrate clearly the effects obtained we shall consider greatly exaggerated faults, but it must be borne in mind that any amount of error, no matter how small, will produce its corresponding fault to a like degree, and only when that degree is so small that it is no longer apparent, is the cranking passably good.

To return to slow cranking: Let us suppose that an actor makes a sweeping gesture which occupies five seconds of time. With normal cranking this will re-quire eighty frames for its registration. When projected, eighty frames will pass through the projector in five seconds, and the action will be normal. Now suppose that the cinematographer cranked only half as fast as usual. Then this action would be registered in forty frames, and when these forty frames pass through the projector, they will consume two and one-half seconds of time, or in other words the action will be accelerated by one hundred per cent. You have seen this effect in the style of comedy which has been discarded for some time. That was, those in which all moving objects darted about the screen so rapidly that the eye could hardly follow them. To obtain this effect the camera was at times cranked as slowly as one-quarter speed.

Now let us consider the error of cranking too rapidly. Using the same five-second gesture for illustration, suppose that the camera were cranked at double speed. One hundred and sixty frames would be used in the registration of this movement, and when projected these frames would consume ten seconds in passing through the machine and the movement would be just twice as slow as in life. This is the principle of slow-motion and motion analysis pictures which most of us have witnessed. There are cameras of the usual port-able type which will expose from two hundred and fifty to three hundred and sixty frames per second or up to twenty-two and a half times normal speed. These cameras, however, are provided with special intermittent movements. It is inadvisable to use the usual type of camera even at double speed, as the film is practically certain to strip and injury to the shuttle is very probable.

It will be seen from the foregoing that the change in speed is directly opposite the change in effect, that is a slow crank gives a fast picture and a fast crank gives a slow picture, but if the film is projected at the same speed as that at which the picture was made, the action will appear normal. This leads us to a more fatal error, one which cannot be remedied by projection at any speed. This is non-uniform cranking.

When turning any crank in a plane perpendicular to the plane of the body it is natural to exert more force on the outward and downward thrust than on the in-ward and upward pull. This means that in making a motiograph that four frames will be made at a fast speed and the next four at a slow speed. In addition to making the projected action alternately slow and fast, this kind of cranking will also alternately over-expose and underexpose the film. Now disregarding the acceleration and slowing, let us see what the result will be at merely fast and slow speeds. We will use the same illustration as before.

For one-fourth of a second the arm will move slowly and the film will be overexposed, and the screen show light, then for the same time the arm will move rapidly and the film will be underexposed. The combined action will be jerky, and as any movement lasting longer than one-sixteenth of a second is perceptible to the eye, the lightening and darkening of the screen four times a second will be very painful to view. In addition, the difference in detail of under-and overexposed film gives a curious illusion of the objects on the screen advancing and retreating. All in all, such a film is utterly worthless and no attempt should be made to save it.

This fault is one which will be found, almost without exception, in films made by an amateur who has not taken the trouble to master cranking before attempting to fill the camera and actually expose film. Examine your camera and be sure, first of all, that you thoroughly understand the mechanical action of the various parts. You may be able to learn to operate an automobile without knowing more of its mechanism than the location of the gasoline tank, but as there are as yet no cine-camera garages, it is essential that you know your camera before trying to operate it. When you are thoroughly familiar with each part and under-stand its function, set the tripod and camera up just as though you were going to make a motiograph, but leave the magazines empty. Now start cranking, and try as much as possible to keep the motion uniform. Crank thirty times or less to the minute if that will help, but keep at it until a uniformity of speed is attained at a reasonably slow speed. Remember that a uniformly slow speed will produce a usable film while non-uniform cranking will not. Passable uniformity has been attained in an hour's practice, but some operators never do acquire it. The time required depends entirely upon the individual. As a rule, the older the amateur, the more difficult is this operation. For middle-aged and elderly persons who wish to enter this fascinating field, the automatic cameras, such as the Sept in standard gauge or the Bell & Howell Automatic in the sixteen millimeter gauge, are strongly recommended.

When uniformity has been attained, learn to crank at the right speed. This speed is almost universally two turns per second. First you must learn to count seconds with fair accuracy. Look at your watch and when the second hand indicates the beginning of a minute, close the watch and count out loud, as rapidly as the words can be clearly enunciated, "One hundred and one, one hundred and two" and so on to twelve, then count deliberately, but not slowly, "Thirteen, Four-teen" and so on. When you have reached sixty, look at the watch. Then try again, counting more slowly or more rapidly than before, according to whether you counted more or less than one minute. When you can count seconds so accurately that you will not vary more than two seconds either way in a minute, begin cranking. The crank goes down on "One" of "One hundred" and also on the number denoting the unit. It also goes down on "Thir" and on "Teen," making two complete revolutions each second. If you have learned the tricks of uniform cranking and of counting seconds, the cranking will soon become second nature. Continue until you can crank correctly judging the speed by cadence rather than actual counting, then continue practice until you can crank correctly and at the same time observe the various actions taking place before your lens, and until you can concentrate on other things. This is necessary, for you will have to be your own director, and cranking must be a matter of habit rather than one of conscious thought.

When you are proficient in cranking, the first great step is past. This should take a week or more. Now learn to thread your camera properly. Upon this depends the smooth running of your camera. However, this is simple and a little care is all that is necessary. Draw out a foot or so of film, making sure that the film has been placed in the magazine in such manner that the film when passed through the shuttle has the emulsion side next the lens. If it does not do this when threaded with loops as directed by the manufacturer of the camera, do not try to remedy it by twisting the film! In this case, the film must be removed from the magazine and the reel reversed. Now draw the film through the gate with the emulsion next to the lens, just as in small cameras the film is loaded with the emulsion facing the lens. In still work, destined for contact printing the diffusion of rays passing through the celluloid base would produce a usable film, but in motion work, the degree of enlargement is so great in projecting that the image must be needle sharp, and this small amount of diffusion would be disastrous.

Now look to the loops. These must be of proper size. That is they must be small enough that the emulsion will not be slapped against the inside of the camera box during the violent vibration originating in the intermittent movement; but at the same time, the loop must be large enough to provide such an amount of slack that the shuttle will not take it all up and drag against the feed sprocket. This would result in strain on the mechanism and the perforations of the film would be ripped out, and in a claw movement the claws would probably be bent enough to cause improper feeding and a "jumpy" picture on the screen.

It must be remembered that the film while passing through the camera has two distinct motions. The film is pulled from the retort magazine by a sprocket which revolves with a constant uniform motion. This sprocket feeds the film into the upper loop or "slack." Then the intermittent jerks the film from this loop a frame at a time, feeding a frame into the lower loop every time it takes one from the upper loop. Just in front of the receiving magazine is another sprocket synchronized with the upper, and revolving with the same uniform movement. In the later and better models, these two sprockets have been replaced by a single feed sprocket, connected directly to the crankshaft. In this type of mechanism the upper side of this large sprocket pulls the film from the retort while the lower side feeds from the lower loop into the receiving magazine. The use of a single sprocket renders it impossible for the two feeds to become dis-synchronized. Reference to the interior view of the Cine-Kodak as published herewith, illustrates this principle. The interior view of the Ernemann camera illustrates this principle also, and perhaps a little clearer. Now trace the movement in the illustration. First notice the large circular box in the upper part of the camera. This is the retort magazine. Issuing from a slot near the bottom of the retort is the film which passes over the upper surface of the large feed sprocket. On the opposite side of the camera, the crank is connected directly to this sprocket. From this it passes into the upper loop. Reference to the illustration will show why this slack is called a loop. From this the film is seen to pass behind a plate of metal which is called the gate. This gate swings open just like a gate in a fence. Directly behind the aperture through which the light rays pass to expose the film, the gate carries an auxiliary plate which is held against the film by springs. This is the pressure plate or pressure pad, and serves to hold the film firmly in contact with the aperture, and consequently in the exact focal plane during exposure. In cheaper cameras this plate has a constant pressure, and care must be taken to see that it is always clean and bright, for any foreign particles would scratch the soft emulsion and streak the film. More expensive cameras have a "release plate" which places the film under pressure only while it is not in motion, thus obviating all chances of scratching. From the gate the film passes into the lower loop, being pulled through the gate by the claws of the intermittent which usually act through vertical slots cut through the margins of the gate. From the lower loop it passes over the under side of the sprocket, and the spindle turning in the receiving magazine takes up all slack from the feed sprocket. Bear in mind that this complete cycle recurs sixteen times every second. For such precise and rapid operation the mechanism must of necessity be somewhat delicate so that you must be sure that all is in perfect condition before attempting to operate the camera. Otherwise you will endanger your equipment. See that the claws fit properly into the perforations and do not strike the film between the perforations. See that there is no dirt, film shreds or other foreign matter any-where inside the camera. See that no dirt is lodged in any dark corners.

There is one point which must be watched. As the spindle in the receiving magazine winds the film, the diameter of the active spindle constantly increases. The wooden spindle usually used will take up approximately two inches at each revolution, but when nearly two hundred feet of film is wound upon it it will take up nearly a foot, and this spindle feeds from the sprocket which revolves at a uniform speed. It is evident that some adjustable feed must be used. This is usually accomplished with a spring belt which slips on its pulley, yet keeps the film tight at all times. Other cameras act by spring clutches. This adjustment is usually made by the manufacturer, but the expert cinematographer always makes sure his take-up is working properly before closing his camera, and he does this each time he inserts a fresh magazine. This is done by turning the crank very slowly a turn or two. If the feed, intermittent and take-up are all working properly the film will move through the mechanism smoothly with practically no effort, and you are ready to make your motiograph.

For your first subject choose one which does not move too rapidly, one which will not necessitate moving the camera while cranking and one which is so well lighted that a stop of f 11 or smaller may be used. This will make for success in your first effort. You can then try more difficult subjects as you become proficient.

The exposure, as such, is regulated in motion work by the size of the diaphragm aperture. It is true that some cameras have adjustable shutters, but this is for a different use as will be described later. This makes the calculation of exposure far more simple than when a sliding scale of the relation between shutter speed and diaphragm opening has to be considered. The motion picture film must possess the utmost possible sharpness, hence the smallest possible opening should be used. Again, contrary to still practice, the absolute stopping of motion is not entirely necessary. The human eye does not register a sharp image of moving objects. As before mentioned, continuity of vision makes us see during an appreciable instant of time all that has occurred during the preceding one-sixteenth of a second, therefore, considerable blurring of the image of a moving object is permissible providing that all fixed objects are perfectly sharp and clear. As long as the cranking speed is maintained, it is nearly impossible to obtain pictures of ordinary objects so badly blurred by motion that this is noticeable on the screen as a defect. Of course, this rule is subject to limitations which will be discussed in connection with the shutter angle. A speed of one-fortieth of a second, which is the approximate exposure of amateur cameras, is fast enough for all ordinary work.

Before making exposures it is well to remember that motion picture film is coated with an emulsion which is rather more than usually sensitive, that the shutter, by virtue of its design, acts with the efficiency of a focal plane shutter and that the extremely small size of the lens results in less absorption of the light rays than is the case with larger and thicker objectives. Bearing this in mind it will be found that a maximum opening of f 11 is ample for most well-lighted outdoor scenes. However, a good cinematograph exposure meter is an essential part of the cinematographer's equipment and is even more valuable than in still work. Get one before you start to work. It will more than save its cost on your first subject.

Also, remember that the negative is not to be printed on paper, but is to be printed as a transparency on motion picture positive stock, and that this comes in but one speed and one degree of contrast. It is common knowledge among photographers that only negatives of the highest degree of technical excellence will give good transparencies. The one control in printing motion pictures, is the regulation in some manner of the amount of light which falls upon the film in a given interval of time. Imagine having to produce a negative which will make an acceptable lantern slide, and which must be printed upon a given grade of lantern slide plate and you will understand the kind of negative which must be obtained upon your motion film. It must be good! This may sound discouraging to many of my amateur readers, but the work will prove to be the best training imaginable for those who have, heretofore, guessed at the correct exposure and let the photo-finisher do his best to obtain a presentable print from the resulting poor negative.

Exposure may be varied, as I have explained, in some cameras, by varying the shutter opening. Such cameras have two shutter blades, one fixed to the shaft and the other revolving about it in such a manner that a sector-shaped opening may be obtained, embracing any desired angle from the maximum opening to entirely closed. Such cameras usually have a maximum opening of 170 degrees. When this auxiliary blade can be closed gradually by automatic mechanism, we have the automatic dissolve which is a feature of professional cameras. Some professional models accomplish the dissolve by closing the diaphragm. In using the adjustable shutter, the speed is calculated in this manner: Estimate the proportion of the opening to the whole shutter and divide sixteen by this. Thus, if one-fourth is open, divide sixteen by one-fourth and the result is sixty-four. Exposure, one sixty-fourth of one second. However, the shutter opening is not changed to compensate for existing light conditions, for when the speed of the subject will admit, the full shutter opening should always be used. The shutter is only closed when photographing subjects whose speed is such that were they to be photographed with full opening the amount of blur would exceed the permissible maximum. Thus, a broadside of an express train or a racing automobile would require a ten degree opening or less, providing the light was strong enough to permit this.

Although the shutter is not altered to compensate for light conditions, a smaller opening does cut down the amount of light admitted to the film and all exposure calculations must take this into account. How-ever, if you possess a camera with an adjustable shutter, I should not recommend such subjects until you are thoroughly familiar with your instrument and its capabilities.

The motiograph requires its own style of lighting. The owner of the small box camera constantly exclaims:

"Get out into the sun so I can snap you !"

The advanced amateur smiles contemptuously at this and usually says :

"I will try an exposure at night, if you like; but as for brilliant sunlight—no, thank you!"

Both are right, considering the limitations of each and the eventual result desired, and in motion work, a little must be taken from each point of view.

We hear much of "Record" versus "Picture." The motion picture is essentially a record. It is true that professional producers with unlimited time, equipment and capital available, have produced motiographs of some artistic value—and more have tried and failed. Also some scenics have been made which vie with salon pictures in sheer beauty; but the scenic motiograph begs the question in that the idea of motion is either absent or suppressed. A little thought will show that the movement of the principals in a dramatic motiograph renders impossible anything more than the most elementary attempts at line composition, and in the same way renders useless most efforts toward orthodox artistic lighting effects, so that the goal of the beginner should be a needle-sharp, brilliantly lighted subject, but one which is not harshly lighted. Now, I can actually hear the host of advanced amateurs rising and shouting, "Brilliant, sun-lighted photography without harshness—how?" The answer is "Reflectors."

We are all familiar with the use of reflectors in indoor work, and we realize their great value in such work, but how many of my readers have used reflectors in photographing a subject lighted by direct, summer sunlight? Very few, I will wager. The professional cinematographer, however, would start on location as readily without his camera as without his reflectors. The usual method is to obtain an oblique, somewhat less than quartering, side-light direct from the sun upon the subject, and then lighten the dark side by the use of reflectors.

The professional reflectors are heavy and sturdy, and incidentally there are men in the crew whose special duty is to handle these unwieldy objects, but for amateur use a light and efficient reflector can be made as follows: Cut two pieces of beaverboard two feet by four. Lay these with the smooth sides facing and along one long edge glue a strong binding strip of canvas. When this is dry the affair can be opened like a huge chessboard and will present a surface four feet square. This surface is now painted with a flat white kalsomine paint. Water color is used so that the surface can be often renewed, easily and cheaply. This is known as a soft reflector and is the one most often used. It reflects a soft, diffused light which used on the dark side of a sunlighted subject will render all detail visible without having to overexpose the bright side, yet a light which will retain all of the modeling of the subject.

In using the reflectors, these are set and the exposure calculated for the lighted subject. The result will be a film of snappy quality, yet with the harshness greatly relieved, the subject perfectly clear in all detail and exposure correct. If the reflectors have been properly set, so that none of the background is illuminated, the subject will stand out with an approximation of stereoscopic relief and with true atmospheric effect, gained not by the suppression of focus in the background, but by the suppression of the lighting.

We have all noticed that of all forms of "one-eyed" photography, the motion picture has the most realistic relief, surpassing even the lantern slide in this respect.

This is not the result of chance, or of some obscure law of optics. It is the result of an incalculable amount of study and experimentation with lighting effects. The most successful device for producing relief by lighting. in common use, is the "hard" reflector. This may be either a beaverboard foundation covered with tinfoil for flood lighting, or a mirror for accenting. The tinfoil may be used with great success by the amateur in place of the mirror and is far more easily handled. No matter which is used, it should be not less than two feet square.

In use, the hard reflector is used to reflect the sun's rays in their full intensity upon the back of the subject. That is, the side away from the lens. Does this sound foolish? It is not so, you may be sure! It is but an adaptation of the backlighting so commonly used in the better class of portrait studios. It gives life and brilliancy to the hair and surrounds the figure with a faint aura. It is essentially a useful application of our old time enemy, halation. Note that this light is not considered in calculating the exposure, but is allowed to "burn up" the film wherever it strikes. For this reason, the hard reflector, used by the amateur, would probably prove disastrous, though it is used extensively by professionals.

The foregoing is analogous to the directions which accompany the little box camera. As the amateur advances in motion work he will find lighting a tool even more flexible than in still photography. He will have many, many failures—and will achieve many beautiful results. The subject of lighting has never been mastered by anyone. However, in this elementary work I am only trying to get the beginner well started on the right path and nothing more, therefore, all rules I give are only basic, and all are possible of the utmost elaboration—and disregard—by the advanced amateur.

Such lighting as I have described will yield the best results for such beginners and as each progresses he will answer for himself the various questions of proper lighting as they come up. The professional will try, at least, to obtain a picture under any light conditions you may give him.

With a knowledge of cranking, threading and focusing and with the reflectors on the field, the cinematographer is ready for business. The matter of focusing and arrangement is about the same in still work, but care must be taken to obtain the finest focus possible, and to this end it is well to remember that even with many fine anastigmats, the focus varies with different diaphragm apertures, although to a degree which would not matter in negative making for contact printing. For this reason, if possible, always focus with the opening which is to be used. Many better grade cameras have micrometer lens mounts which automatically compensate for the diaphragm stop, when setting the lens. The lens is first focused wide open, and then as the diaphragm is set, the focus is changed to compensate.

The last thing to do is to establish the sidelines. In professional work, actual marks are now rarely used, but the amateur should use them until familiar with his work, and they should always be used when utilizing amateur actors, so they may know when they are included in the field of the lens.

While looking through the finder, or better, the focusing tube, have an assistant walk across the field of view, about ten feet distant from the lens. As he just enters the field of view, have him make a mark on the ground, then as he walks out of the field have that point marked also. Then repeat the process with the marker at a distance of thirty or forty feet. Now connect the points on each side. These two lines will enclose an angle whose apex lies just under the lens.

This is the angle of view of the lens and all action must take place within it or be lost to the camera. Now have the assistant begin at the camera and walk directly away until his feet come into view. Mark this place for the front line. This is for full length action. In close-up work, of course, this is disregarded.

All is now ready for the actual exposure; but it is quite a trick to obtain a presentable picture. For this reason, a certain amount of rehearsal and direction is necessary, so these subjects will be discussed in the next chapter.



Home | More Articles | Email: info@oldandsold.com