Back in those daredevil days before computers, when commercial lithographic printing was film based, orthochromatic films were created to render nothing more than 100% black and 100% clear. The total lack of middle tones made these films ideal to rephotograph type or, in the case of color images, reproduce them as black dots of varying sizes, one piece of film for each ink color; yellow, magenta, cyan, and key (black). This CMYK color space is still used today, of course, but is now created digitally.
The most popular ortho film was Kodalith, available in many sizes from full-plate sheets to 35 mm. Photographic ...