Movie Makers (Jun-Dec 1928)

Photographs by Metro THE CAMERA SAW NO CLOUDS ON ORDINARY FILM WITHOUT A FILTER whatever on the photographic emulsions of the older type, called ordinary emulsions, and yellow light which is very bright to the eye has very little effect on these same emulsions. The processing of the film transforms the component parts of the sensitive material into layers of metallic silver. This transformation is always of the same order, that is to say, metallic silver is always the result of the reaction irrespective of the color of the light which has caused it, but its density varies according to the color of the light as well as according to its intensity. The photographic image is then only a translation of the colors in layers of silver of different densities which, when looked at by transparency, gives the impression of the lights and shades of the scene which has been photographed, as the sensitive emulsion sees it. The mentioned intensity factor of light we will dismiss from our mind because it is very elemental for anyone who has been even a little familiar with photography that a certain amount of light is necessary to make an impression on the film. The color factor is the one that controls the chromatic or color rendition of the scene or object photographed and it is the one which is of present interest. All colors are distinguishable through the impression that they make upon the eye. Some of them appear brighter than others and viceversa. This we will call the visual rendition of the colors. The yellow, for instance, is the color which produces upon the eye the effect of greatest brilliancy; the green appears less bright, the blue still less, while the orange and the red affect the eye with different degrees of brightness if compared with the yellow, but we will al 584 ways find a certain color which presents to the eye the same brightness as another color such as, for example, a green and an orange which are distinguishable by the eye only through the difference in their hue. We may then visualize the different colors ranged on a band having the yellow in the center, the greens, the blues and the violets fading away in brilliancy on one side and the oranges and red fading away on the other side. Such band would appear approximately as illustrated in the center of Figure 1, if abstraction is made of color and brightness only is considered. To obtain a correct rendition of all colors the photographic film should so react under the different colored lights that the layer of silver should have its greatest density in the yellow, a lesser density in the green and orange and a still lesser density in the blue and red, so that when a positive is printed or obtained by reversion of the image, the yellow would result as the most transparent and consequently the brightest on the screen during projection, as shown in the right hand band of Figure I. But this does not happen with ordinary orthochromatic emulsions. The sensitive material is affected in greater proportion by the blue light than by any other one included in the whole range of colors, so that when the positive print is obtained the colors are translated in shades of grays which are the brightest in the blues and gradually shade away on each side of it so that the oranges and reds appear black and some of the colored lights which are even invisible to the eye beyond the violet range of colors are photographically reproduced as shades of grays, as shown in the left hand band of Figure 1. It is quite obvious that such rendition is contrary to the true appearance of an object or scene to the eye and that it entirely depends upon the quality of the sensitive material used in photographing such object or scene. As far back as 1873, Vogel, one of the early experimenters in the then newly developed science of photography, discovered that if a photographic emulsion were treated with special dyes, its sensitiveness would increase for lights of a yellow color. This discovery which brought about a correction in the photographic rendition of colors prompted Vogel to call "orthochromatic" the photographic plates prepared with the incorporation of the dye. Orthochromatic is a word derived from the two Greek words "orto" and "chromo" which mean respectively correct and color. This appelation was quite pretentious. Although a great improvement in the photographic color rendition was brought about by Vogel's discovery, it was far from corresponding to the exact visual impression that the colors have upon the eye. But it was a beginning, a great beginning. It came to be one of the cornerstones upon which the great and complex edifice, to which modern photography can be compared, was built. And so, the cornerstone firmly laid in position, scientists busied themselves in their laboratories with the discovery of the reasons and physical laws underlying and controlling the sensitiveness of photographic emulsions for the different colors. Through constant effort and patient research new dyes were discovered, difficulties of treatment were little by little eliminated and gradually the new emulsions left the experimental realm of the research laboratory, went into the world and began their glorious career. At first these emulsions required a great amount of precaution and skill in their use, which difficulties did not permit their adoption outside of a limited professional field. But these difficulties were gradually ironed out and the sensitiveness of the emulsion for all colors was constantly increased without damaging its other essential qualities. From the yellow the sensitivity was gradually extended to the orange and then to the reds and the appellation, pan-chromatic emulsion, was finally adopted because its meaning, "pertaining to all colors," was in true keeping with its qualities. The improvements in the quality of the emulsion and the minimization of the difficulties encountered in its use have brought this product of human intelligence to the door of the amateur