A special film is prepared, consisting of three separate emulsions on one support. The top emulsion is sensitive to blue light only. Beneath it is a layer of yellow dye, which absorbs the unrecorded blue rays, allowing the red and green rays to penetrate to the two emulsions beneath it, one of which is sensitive to green rays only, and the other to red. Thus a simultaneous record is obtained of the three primary colors. After exposure the film is developed to a negative and then, by chemical means, is converted to a positive. During the processing special substances are introduced, dye-couplers, which cause the three emulsions to take on the appropriate complementary colors: yellow, magenta and cyan. The processing requires complex machinery and is done by the manufacturer. To answer the demand for a film which the photographer could process himself, Ansco brought out in 1942 its Ansco-Color film, which was followed by Kodak’s Ektachrome film.
These techniques have the same limitation as the daguerreotype and the tintype: each color photograph is unique. A more recent development makes use of the negative-positive principle. Kodacolor film, announced in 1941, is similar in general principle to Kodachrome film, except that the image is not reversed to a positive and dye couplers are chosen which will convert each emulsion to an image complementary to the color which it records. Thus a color negative shows not only reversal of the lights and shades, but also of color. A blonde will appear with blue hair and green lips. From this negative any number of prints can be made by repeating the process with identical triple emulsion coated on a white opaque material.
Using Ektacolor film, announced by the Eastman Kodak Company, in 1947, the photographer can process his own color negatives. An important feature of this new technique is the incorporation in the film of a mask which automatically compensates for inaccuracies in color rendition. Theoretically it should be possible to choose dyes which will completely absorb each of the primary colors. In practice this cannot be done. To correct these errors, the dye couplers added to the emulsion are themselves colored, absorbing the very rays which are incorrectly absorbed by the dyes. From the Ektacolor negative three gelatin matrices can be made directly for printing by dye transfer.
For reproduction on the printed page, transparencies are rephotographed by normal means and through the primary filters: from each negative a printing plate is made, usually by the halftone process. The paper is run through the press four times, with cyan, yellow, magenta and black inks.
The color photographer is faced with many esthetic problems. The eye does not see color the way the camera does. Should he choose the naturalistic approach and, as P. H. Emerson did in black and white, limit himself to reproducing what the eye sees? Or should he follow the camera’s lead, exploiting its potentials and respecting its limits? There seem to be colors which exist only in photographs: Kodachrome film, for example, gives blue of a richness and depth which can validly be used for its own sake with no attempt at realism. Already work has been done in every field with color; practically every photographer has worked with the new techniques, and although the complexity of processing and the expense of materials has been a deterrent to free experimentation, the esthetic capabilities are being explored.
The temptation is to choose subjects which are themselves a blaze of color, and to ignore the fact that color is everywhere, and that it is not the colorful subject itself, but the photographer’s handling of it, which is creative. The most satisfying results appear to be of subdued colors, with here and there a brilliant, telling accent.
Comparison between color photography and painting is inevitable. Imitation is fatal, for the color photographer does not have at his command the controls which enable the painter to produce his own world of color. On the other hand, the photographer has a medium which the painter cannot rival, an instantaneous process, which will record the vision of a moment with wealth and subtlety of detail beyond the power of the most skillful draftsman to reproduce.
The scope of color photography is being rapidly expanded; fields which only a few years ago seemed closed are now being explored with success. Similar expansion is taking place in every other branch of photography.
As Hurter and Driffield pointed out, photography is at once a science and an art. Its growth as a science has been a steady development from the inexact and capricious technique of Daguerre to the perfection of reliable, high speed emulsions; from the simple meniscus lens of Chevalier to the modern coated anastigmat; from the cumbersome box camera of Talbot to the precision miniature. Yet as pictures many of the earliest photographs remain unexcelled. The portraits of Southworth and Hawes and of Hill and Adamson are great portraits. If the action of war can now be recorded, its havoc has never been more poignantly interpreted in photographs than by Brady and his colleagues. We make no finer records of architecture than did the calotypists of the 1850’s.
For the artist has always transcended his materials. Through his special vision we see the world afresh. In every photograph the moment is fixed forever. In some it is the very moment that we prize, because it is such vivid history. In a few the moment magically becomes forever.