The Smith system was based on the fact that in tricolor projection, the blue-violet constituent adds but little color as such. It brightens up the other colors and forms white. It does provide the pure blues and violets. But white is but a relative term and we accept as white in two-color projection that which is actually a yellow. The process was actually an additive one, and the black and white positives were projected through red and green filters, which were not of quite the same shade as the taking filters.

At the present time the efforts of most inventors seem to be directed to the production of subtractive pictures, in which each picture is itself a complete color record, and although but two colors are used the results in many cases are extremely pleasing. That the colors are absolutely true cannot be upheld, but the lack is so small that the average observer can rarely detect it. Moreover the question of color, whether in an oil painting or a photograph in colors, is so much a matter of individual feeling that probably no two critics would be in strict accord as to the correctness of a particular color rendering.

The processes that are used are to some extent secrets; but they would all be found to fall into the relief or mordanting methods already described. The use of double-coated film, that is, film with emulsion on both sides, is fairly general. While this facilitates the process in that one has two distinct images that can be appropriately colored, it introduces other troubles in the shape of rigorous necessity of registration, and it is obvious that care has to be exercised that each image is confined to one side of the emulsion.

The production of motion pictures in colors offers an enticing field for the experimenter, but it is beyond the reach of the average worker, as the outlay for the apparatus is heavy. Should anyone be desirous of entering this field, the soundest advice that can be given is to study the two or three hundred patents that have been issued on the subject, as no practical details have yet found their way into print. It should be borne in mind that a subtractive process with the colors on each picture on a single film that can be run through any projector is the desideratum.

Whether a three-color subtractive film is within reasonable reach of perfection is not known; but there are two or three two-color subtractive processes which threaten to become commercial within a reasonable time. Even if the cost of the production of the film can be kept down within reasonable limits, because after all this is an important question, it is a debatable point whether the public is sufficiently educated to pay more for seeing pictures in colors, and whether it would be more attractive to the multitude to see Charlie Chaplin fooling in colors than in black and white.