With the introduction of better inks and Kodachrome film during the 1930’s, the tricolor method evolved into process printing. With a more accurate color film to base images on, colors could now be separated with process cameras instead of by the whim of a retoucher, and then each halftone negative would be used to exposed a separate printing plate. The typical RYB pallet used in tricolor printing was replaced with CYM process colors that better suited optical theory, but as they tended to create a muddy brown when overprinting each other, a black plate (represented by K) had to be added to the mix. Even the best of the early tricolor prints that produced realistic looking colors weren’t quite real enough. Since Kodachrome comes very close to capturing natural color, attempts to improve on it by hand no longer needed to be made. Postcards going forward would not only be printed in natural color, the imagery they carried would appear more real. While some line blocks incorporated process printing techniques, this technique would largely be used in conjunction with lithography and latter offset printing. The first images made from Kodachrome were far from perfect; colors were often unsaturated and contrast was poor. A year after the film underwent major changes the first process printed postcard based on it was made in 1939, and they would be called photochromes. Over the years however the color accuracy and saturation of Kodachrome improved along with the printing techniques that employed it. Today most people refer to process printed photochromes simply as chromes.
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