The perfection attained in the projection of animation upon the screen in black and white naturally stimulated efforts towards the achievement of similar results in natural colours. As a matter of fact, experiments in this direction were undertaken long before monochrome cinematography was perfected. W. F. Greene indicated the development when he produced his instrument in 1889; while as far back as 1897 Frederick E. Ives, celebrated for his efforts to solve the problem of still-life natural colour photography, outlined a means of applying his process to cinematography with glass plates, the celluloid film not having appeared at that date. No doubt he was urged to this development by the wonderful results achieved in chronophotography with glass plates by Dr. Marey in Paris.

Since that year experimenters without end have grappled with the problem; but little material success has been achieved. Indeed, commercial cinematography in the true colours of Nature appears to be as far from realisation as a simple process of still-life colour photography. Nature defies the photographic investigator to capture and reproduce the myriad tints and hues in which she is garbed.

We see colour pictures upon the white screen, but with one or two exceptions the tints are the result of the artist’s handiwork. An ordinary black and white film is taken, and then coloured, in the same way that the photographic artist tints his portraits. If the work is skilfully performed the results are distinctly pleasing and effective. After one has been watching brilliant black and white pictures, the introduction of a coloured film comes as a restful interlude to the eyes. The coloured cinematograph film was introduced by Robert Paul, shortly after he established his studio. As lantern slides could be coloured by hand with brush and paints, he saw no reason why a film 40 feet in length should not be treated in the same way. Accordingly he enlisted the services of an expert artist to make the experiment. But it was a laborious undertaking. A picture measuring only 1 inch wide by ¾ths of an inch in depth is a base of operations quite different from a lantern slide measuring 3¼ inches square. A magnifying glass had to be used, and a considerable length of time was needed to treat a whole film.

One of the earliest colour effects to which the public were introduced was a film produced by James Williamson, in the ’nineties of the last century. It depicted a fire. The conflagration was enacted realistically, an abandoned house being used for the purpose. The flames and the entire scene were coloured, giving additional sensationalism to the picture. At that time the coloured film was very rarely seen, owing to the expense involved in its production, and when Williamson put his handiwork on the market it received an extraordinary reception. The lurid tinting of the flames caught the public fancy.

When the film measuring 400 feet or more came into vogue it was recognised that hand colouring was no longer feasible. The method was too slow and costly. Accordingly a stencil process was evolved, and is in use to-day, giving many of the beautiful effects seen in the moving picture theatres. A mechanical method of tinting the films by means of these stencils was next taken in hand, and finally, after prolonged experiment, was perfected. In this development the French firm of Pathé Frères played the most prominent part, and to-day, despite the strides made in natural colour cinematography, their productions still rank first in popular estimation, owing to the delicacy of the colouring. This Parisian firm has made the colour film a prominent feature of its business, and laid down an extensive and well-equipped establishment especially for colouring operations.

Probably everyone knows what a stencil is. It is a pattern cut out of a solid thin flat surface, which is afterwards laid upon the subject to be treated, and paint applied by means of a brush or some other medium. The colouring only can reach the surface beneath the cut spaces in the plate, and consequently is applied just where it is desired. The process is practised freely in the printing of wall-papers, and in applying designs to other surfaces, as it is both cheap, rapid, and highly effective.

Cutting the stencils for a moving picture film is a long and exacting task. Three stencils have to be prepared for each subject. In the first the spaces corresponding to the red tones in the picture have to be cut; in the second, those for the yellow; and in the third stencil, those for the blue. By putting one over the other the various mixtures and tones are obtained. The process may be likened to the preparation of the three process blocks for heliochromic illustrations in letterpress printing. Since each picture measures only 1 inch wide by ¾ths of an inch in depth, we may gather some idea of the labour involved for the treatment of, say, 8,000 pictures contained in a film 500 feet long. It follows that unless a film is likely to have a large demand, colouring is not attempted. In one case which I have in mind, the firm will not attempt colouring unless they are certain of the sale of 200 copies of the subject. The colours—aniline dyes—are applied successively by means of rollers, the film to be coloured being passed through special machines contrived for the purpose.

In view of the expense and time entailed, it is not surprising that many inventors have devoted their energies to devise ways and means of taking colour pictures direct from Nature. Greene evolved the first cinematographic process for taking and projecting moving pictures in natural colours, and his patent constitutes the base upon which all other experimenters have worked, just as to-day in America the kinetoscope is regarded as the progenitor of the cinematograph. Six months later another process working upon the same broad principle was patented by Lee and Turner. But Greene’s process was premature; at that time it was unworkable. The Lee and Turner system, fundamentally the same, suffered from a similar defect, as I shall explain a little later.

Natural light is the result of waves oscillating at a tremendous speed per second, just as other waves, heavier and travelling far more slowly in comparison with light waves, produce sound. Our familiar conception of natural light, or daylight, is that it is white; but we also know that when a narrow beam is permitted to fall upon a length of glass of triangular section, known as a prism, the light which on the outer side appears white is found to be resolved into colours on the opposite side. In passing through the prism the beam of light has been deflected from a straight path, and the result is that the waves of varying length, of which white light is composed, have been sorted out. The shortest rays are red, while the longest rays have a violet tinge. The analysis of light, as revealed by the spectrum in a dark chamber, is performed for us by Nature in the rainbow.

If we examine that phenomenon we shall see that the innumerable tints constituting it fall into three broad groups—red, green, and violet. These therefore are regarded as the primary colours. By combining any two, or all three, of these, the multitudinous hues with which we are familiar may be produced. The average person, when he hears red, green, and violet described as the primary colours, is inclined to remonstrate. At school or when using his box of paints, he was taught to regard yellow, red, and blue as the primary colours, and green, a mixture of blue and yellow, as a secondary or complementary colour. But the two instances deal with totally different forms of light. The former is transmitted, and the second is reflected, light. This confusion of thought led to the undoing of many early experimenters in colour photography. They took their images through successive screens of red, yellow, and blue, and when projecting used the complementary coloured screens—orange, green, and violet. The results were startling. It was not until Greene took his pictures through the red, green, and violet screens, and subsequently projected them through screens of the same colours—that is to say, the picture taken through the green glass was projected through the green glass, the red through the red, and the violet through the violet—that any tangible progress was made.

When the celluloid film came into vogue the experimenters lost no time in commercialising a system of natural-colour cinematography. The idea was to take a picture through each successive screen. In other words, the first picture was taken through the red screen; the film was jerked forward, and the second picture was taken through the green screen; lastly, a fresh area of sensitised surface was brought before the lens and third or violet screen. Thus three consecutive pictures, taken through three different screens, were secured. The screens comprised sectors of red, green, and violet respectively, each colour screen being succeeded by an opaque sector. Thus the shutter was divided into six parts—three colour screens and three opaque sectors alternately. After exposure through one screen, as the following opaque sector flitted across the lens, the film was jerked into position to bring a fresh surface of sensitised surface before the next screen in the revolving shutter.

When the red screen is brought into position before the lens, the colours in the object are filtered, as it were, only the red rays being permitted to pass through the screen to the film. The picture on the film, therefore, is a photograph of the red tones in the subject. Similarly the green screen absorbs all but the green rays, and photographs a record of the green tones in the subject. The same is true of the violet screen. The developed film possesses no tinge of colour in itself. It is merely a black-and-white image. Close examination of three consecutive pictures, however, reveals varying densities according to the filtering action of the respective screens. In projecting, the picture taken through the red screen is thrown through a red screen, the green image through a green screen, and the violet though a violet screen. Thus the lantern reconstructs upon the sheet what the camera dissects when photographing the object. Experimenters anticipated that, in virtue of the law of visual persistence, if these pictures were projected at a sufficient speed upon the sheet, the three images taken through the red, green, and violet screens would be superimposed one on the next, thereby conveying to the eye a faithful colour record of Nature.

It sounds feasible and seems attractively simple to perform; but Nature has not been caught yet.

At the very outset the investigators were baffled. The sensitised emulsion on the film was too slow to render the application possible. Every photographer knows that the red light is non-actinic—he uses it for the illumination of his dark-room while developing his plates. Obviously, therefore, it was hopeless to endeavour to take a photograph through the red screen in 1/100th part of a second. For this reason Greene’s process failed, as did also that of Lee and Turner.

Then another miscalculation was revealed. With black-and-white pictures a speed of sixteen pictures is the minimum capable of conveying the impression of continuous motion to the brain. As the pictures are in monochrome, the perfection of the illusion is facilitated. But when it came to projecting the pictures taken in three different colours, one after the other, this law was seriously upset. When only sixteen pictures per second are shown, the eye and brain are able to single out the respective colours. The pictures do not run together to give a natural colour-effect, but are merely successive flashes of red, green, and violet light. Accordingly, the rate of projection had to be increased three times at least—forty-eight pictures per second—and the strain of this speed upon the film was so great that often it succumbed.

Consequently, before colour-cinematography could advance beyond the year 1899—when the first patent was filed by Greene—the chemist had to be called in once more to accomplish a miracle and make possible the dreams of inventors. The sensitised emulsion had to be speeded up to such a degree that it was sensitive even to red light. By this means the film is made “panchromatic,” as it is called; that is to say, it becomes so sensitive that it will permit an exposure to be made as rapidly through the red as through the green screen. But “panchromatism” brought its own drawbacks. The film could no longer be handled in the dark-room illumined with a ruby lamp, for fear of becoming fogged.

It has not been found practicable to impart panchromatism to the film at the time it is manufactured. I do not mean to say that it cannot be done at that stage, but the demand for such a film is so small that it is not worthy of present consideration on the part of the manufacturer. Until colour-cinematography becomes generally practised, those engaged in its exploitation will be compelled to render their film panchromatic preparatory to exposure.

This means that the film as it arrives from the manufacturer must be submitted to a preliminary operation to augment its sensitiveness to light. For this purpose it is passed through a “colour-sensitising” solution. The precise constitution of this sensitising bath is jealously guarded, though the materials employed in the process are well known, and several formulæ which will render a film panchromatic have been published. Any one of three chemicals can be utilised to render the ordinary film so sensitive to light that the ruby lamp will fog it. These are pinachrome, pinacyanol, and ethyl-violet. The proportion of these fundamental chemicals varies, the majority of investigators having evolved a particular formula which they have found to be the best suited to their own requirements. The published formulæ, however, have proved quite reliable, and have been productive of some excellent results; and they provide the experimenter with a basis upon which to carry out his work. Recently a further development has been recorded. W. F. Greene, the pioneer, has successfully employed a new colour sensitiser, which is faster than either of the three above-mentioned mediums.

Panchromatising is a tedious operation. The work has to be carried out practically in total darkness, or at the utmost in the faint glimmer of a blue-black light. Even this slight illumination has to be used very sparingly, being switched on only for a few seconds at a time. After being passed through the colour sensitiser the film is wound upon a large drum and dried, this operation being accelerated by rotating the drum at a high speed in a current of warm air. When dry the film is wound upon the spool ready for use. As may be supposed, the operation is somewhat slow, about three hours being occupied under the most favourable conditions in the process of sensitising and drying.

It is imperative that the film, after being sensitised, should be used as soon as possible. It deteriorates rapidly; the sensitiveness of the emulsion to red light becomes impoverished through keeping, the life of stock so treated being, as a rule, one of only a few weeks.

Another objection to colour cinematography is the expense. When the three primary colours—red, green, and violet—are used, demanding a photographing and projecting speed of forty-eight pictures per second—sixteen per second through each screen—as compared with sixteen pictures per second with black and white work, three times the quantity of film has to be used. Accordingly, the expense of the film alone is three times as heavy. The further necessity for panchromatising the film before use increases the cost of the material still more. By the time the “stock” has been treated with the colour sensitiser its cost is increased from 1½d., or 3 cents, to about 3½d., or 7 cents, per foot.

When tricolour cinematography is attempted, three feet of film are required to record the movements of the subject during the space of one second, as against one foot for black and white work. With a view to reducing this heavy cost, inventors concentrated their attention on the possibility of securing approximately true natural colours by the aid of two screens only—the green and the red. In this way a third less film was required and the cost was reduced by an equal proportion.

This development was led by W. F. Greene. Realising the disadvantages of the three screens, he abandoned that system—although it has since been exploited—and in 1905 perfected the first practical method of natural-colour cinematography through two screens—red and green. A demonstration was given in the Library of the Royal Institution on January 26th, 1906. This was not Greene’s first demonstration in two-colour work, as in 1900 he devised a machine for achieving the same object, which was exhibited before the Royal Photographic Society in that year.

Another diligent investigator in this field was Mr. Albert Smith, who was striving towards colour cinematography at the same time as Greene, but independently of him. The art fascinated him in the early days; and although he prosecuted his experiments first in black and white, the result of Ives’s efforts in still-life colour photography prompted him to wrestle with the problem of producing natural colours in moving pictures. The elimination of the third or blue screen was his special study, and years were expended in researches to this end, involving countless experiments with the red and green screens, varying in density and intensity from the colour point of view, and in relation to one another. For instance, one screen, say, of emerald-green and the other of orange-red would first be used. This proving unsatisfactory, the proportion of the red in the one screen was increased, the green remaining untouched. Then the green would be varied, and then the red again, the process being continued until a satisfactory result was obtained. The search was rendered all the more exasperating when the screens which produced satisfaction on one day with a subject, failed altogether with another subject the next day, owing to variation in the light. At last, in 1906, Mr. Smith’s patent, known as “Kinemacolor,” made its appearance some eighteen months behind that of Greene; though it was not perfected sufficiently to be introduced to the public until 1908.

Undoubtedly “Kinemacolor” is at present the best-known commercial natural colour system. The appearance of this process has stimulated the movement in colour cinematography to a pronounced degree, and its improved appearance in 1911 created a sensation. Some of the effects produced have been very beautiful, and although they are far from perfect, as those identified with the process will readily admit, yet it constitutes an excellent stepping-stone for further improvement.

The statement that the blue screen has been eliminated will doubtless provoke discussion as to how the hues of a pronounced blue or purple effect so common in nature can be obtained. If one picture is photographed through the red screen and the second through the green screen, this alternation of exposure being continued throughout the film, it seems certain that the result will be pictures wherein only green and red tones exist, since no combination of these colours will give purple. This, in fact, is the case, and it constitutes the foremost imperfection in “Kinemacolor”; the pictures do have a prevailing green or red tone. But these tints become modified slightly. The essential blue tone is partially supplied in two ways. In the first place there is a certain proportion of blue associated with the green screen; secondly, when the electric arc light is used there is a pronounced blue tone in the light. The combination of these factors, to a certain but very small degree, compensates for the absence of the blue screen.

On the other hand, resort to the two screens serves to emphasise the direct colours. The red and green tones do stand out with startling purity—“unnaturally vivid” is a criticism that I have often heard—but the intermediate tones, particularly those of the browns, are strikingly soft. Some of the pictures are assailed as being unnatural in tone; and to a certain extent the criticism is a just one. In some instances, however, it is due to the fact that the spectator has never actually concentrated his attention upon colour effects in Nature. His eye has never given him a faithful report of their quality.

That “Kinemacolor” has severe limitations cannot be denied, especially when it comes to dealing with Nature direct. Fidelity to the myriad hues of Nature, ranging from one extreme end of the spectrum to the other, cannot possibly be obtained by recourse to two screens.

One searches in vain for the true blue and the rich, deep purple, while the pure yellow also is absent, being represented by varying tones of orange. So far as the blues and purples are concerned, they never can be obtained by resort to the two screens—red and green respectively—because what is known as the lower end of the spectrum is lost entirely by “Kinemacolor.” The hues stop short at the boundary where green meets blue.

The public has sometimes drawn attention to another defect in colour cinematography. It appears to photograph the subject in a brilliant sunlight, regardless of the fact that sunlight kills colours. Every amateur photographer knows that if he exposes his plate upon a brilliantly lighted subject the tones are hard, everything being practically resolved into an intense white and black, while the leaves of trees appear to be covered with snow. When such a disadvantage afflicts the black and white worker, what can be said of a colour subject taken under the same conditions? The brilliantly lighted points are lacking in tone, and some very bizarre effects are produced in consequence. When an essentially scenic subject is thrown upon the screen these defects are very manifest, but when it is applied to such a subject as the Coronation of the King the flaws are overlooked, because public interest is concentrated upon the principal actors.

It cannot be denied that from the popular point of view the Kinemacolor records of the Coronation, the Investiture of the Prince of Wales, and other Royal subjects of the same time left little to be desired. They brought the scene before millions with a wonderful realism and gorgeous blaze of colour such as never before in the history of moving pictures had been witnessed upon the screen. The excellence of these portrayals established “Kinemacolor” firmly in the mind of the public.

Another disconcerting feature which has aroused considerable comment in the public mind is the apparent duplication of the outlines of figures near the camera. The most uninitiated observer cannot fail to see the outlines in green and red, as if the superimposition were out of register. “Fringing,” as this defect is called, is difficult to eliminate in many instances, and although often it is only momentary, it is decidedly distressing. It is due to diffraction, the glass screen as the light passes through acting somewhat as a prism, and splitting up the light into its component parts or groups of wave-lengths.

“Kinemacolor” has vast possibilities in the presentation of picture-plays; indeed, this may be said to be its true province. Here one can prepare the scenery and costumes to come within the limitations of the two screens adopted; the drawbacks can be eliminated by proper staging, and all those colours omitted which cannot be faithfully reproduced. Even if the latter expedient is not practised, the colour-distortion is not seen upon the screen. The audience cannot see that a rich purple cloak has turned to a whitish-green, or a brilliant yellow become reddish-orange.

In justice, however, it must be said that Kinemacolor is only in its infancy; it occupies the same position to-day that black-and-white cinematography did in the early ’nineties. The combined efforts of several independent investigators will eliminate the defects one by one and effect steady improvements. Black-and-white cinematography has passed beyond the formative period and reached an advanced stage of development; natural-colour cinematography must go through the self-same ordeal. Operators have not become accustomed to the new order of things, and have not realised the many new factors that have to be taken into consideration. The sooner they do so, the more profitable will the art become.

A new rival, “Biocolor,” has recently made its appearance. This process is based upon the Greene patents, and the results achieved so far, in combination with this indefatigable experimenter’s latest discoveries, represent a marked advance in the art. Not only are the tones purer to Nature, but “fringing” and other defects have been eliminated, while the process is much simpler and cheaper.

Considerable attention has been centred upon a new natural-colour cinematographic process which has recently made its appearance. The three primary colours are used, and are projected upon the screen simultaneously to present merely one image before the public, as in the Ives system of lantern-slide colour-projection. The pictures are projected at the rate of sixteen per second in groups of three, and the lighting arrangement is carried out upon different lines. Instead of a revolving shutter eclipsing the red image to permit the green picture to be brought into place, the light is extinguished, projection being carried out upon a flash system, whereby a powerful beam of light is thrown momentarily through the three images and screens, the pictures being changed in the period of darkness. The flashing must be carried out with uniformity, which is assured by electric-mechanical means, independently of the operator. The results, it is stated, show the most distinct advance so far made in natural-colour cinematography.

Although colour-cinematography has made remarkable strides, the monochrome picture has become established more firmly than ever. The appearance of the new rival has stimulated perfection in the technical excellence of the latter process. The monochrome possesses one overwhelming advantage over its competitor—it is far cheaper. A subject which in black and white requires, say, 500 feet of film, demands, as we have seen, 1,000 feet, or twice the quantity of material, for the two-colour record of the same subject. At present also the monochrome film possesses finer and more brilliant detail, is clearer, and, from the photographic standpoint, leaves little to be desired.

It is becoming quite a common practice to relieve the monotonous black-and-white by the introduction of colouring effects. For instance, the impression of a bright moon-light night is conveyed by giving the pictures a prevailing blue tone; for other scenes brown or red tones are given. These effects are secured by steeping the film in a chemical solution in precisely the same way as platinotype and bromide papers are tinted after development.

“Toning,” as it is called, is coming into extensive use, especially in connection with the most artistic films. The treatment imparts a solidity to the figures in the picture, and gives a pleasing softness, so that the pictures upon the screen possess a quasi-stereoscopic effect highly pleasing to the eye. The beauty of this treatment is revealed very significantly in the films of Italian manufacture, and especially in the “art” productions of the Cines Company, of Rome. There is no limitation to subsequent improving processes such as these, and their effect is to implant the monochrome pictures more and more firmly in public estimation. Consequently, the black-and-white picture is far from being eclipsed by its new rival; in fact, such a contingency is more remote to-day than it was ten years ago.