Movie Makers (Jan-Dec 1938)

286 At right, effect of a yellow filter; below, the result of heavy red filter WHERE FILTERS FIT IN CAPT. D. W. NORWOOD, U.S. A., ACL FILTERS are such important factors in improving the quality of pictures that no movie maker should ignore them when he is working in black and white. They help the cameraman to get the most out of his investment in equipment and film. The use of filters may be simple or involved, according to the photographic experience of the individual concerned, but at every stage of the game they will improve the results on the screen. Color filters perform three important services in black and white photographic practice. First, they are used for color correction, to give correct tone representation of colors; second, they are used for haze penetration; third, they are used to emphasize color contrasts for special effects. When considering filter use, it is well to have in mind the three principal types of black and white films available to the movie maker. First is the color blind, or positive, type, which is sensitive largely to blue light; it is not practical to use William M. Rittase Harold M. Lambert from Black Star filters of any sort with this film. The second type, orthochromatic, is sensitive to all colors except red; almost all filters except red ones may be considered satisfactory for orthochromatic film types. Third, and last, is the panchromatic film, which is sensitive to every color and which is suitable for use with all common filters. To understand the first function of filters, that of correct tone representation, it is necessary to know that, while all of the colors of the spectrum are of equal intensity, they do not appear so to the eye. Some colors, such as orange and green, appear bright to the eye, while others, such as blue and maroon, do not. Photographic emulsion also is more sensitive to some colors than to others but, unfortunately, to a different group of colors, which complicates matters. Were the eye and the film emulsion equally sensitive to the same range of colors, there would be no need for color correction through filters. But this is not the case. For example, the film sees ultra violet and blue as the brightest colors. In fact, the film is so sensitive to ultra violet and blue that it records them as if they were white. An example of this is seen when white clouds in a blue sky are included in an unfiltered shot. The blue of the sky may be registered as white, and the white clouds may not be distinguishable in the field of white. Another example of this is found in an unfiltered photograph of a blue eyed person. No matter how deep the blue of the eyes, they are likely to appear pale in the picture. To compensate for the differences between the eye's sensitivity to various colors and photographic film's sensitivity to the same colors, it is necessary to use filters which will absorb some colors, partially absorb others and pass still others without any absorption. By this means, it is possible to record, on the film, light intensities from the various colors with approximately the same relative values as perceived by the eye. This is called color correction. In pictures made on panchromatic film with a filter, the sky has some depth of tone, and white clouds will stand out as white clouds. The eyes of a blue eyed person will be a pleasant shade of gray, in the screen image, rather than almost white. One can avoid the "bald sky" which is so unpleasant on the screen, and light objects will not be lost against a background of glaring white. Two ex What these useful movie aids can do in amateur films amples of filter use are illustrated here. One of them, the picture of the couple at the beach, shows the effect of a medium yellow filter; the [Continued on page 302]