Getting the picture - Subtractive color mixing with an inkjet printer

Abstract

When teaching colors, physics teachers ask their students to ignore what is taught in art classes and embrace a primary color system of red, green, and blue. This scheme is additive and all colors can be generated by combining light of these three colors with varying intensities. There have been a number of demonstrations and tools to help students understand additive color mixing, using LEDs, color monitors, or similar technologies. However, the subtractive primaries of cyan, magenta, and yellow have received far less attention, if students have previous knowledge it is from printer ink cartridges. This gap may exist because as pigments it can be harder to vary their intensities in real time. Fortunately, our colleagues in the art department are well-versed in subtractive color mixing, and have taught this topic for many years through the lens of color printing. We steal a page from their book and describe how to create a color image using cyan, magenta, yellow, and black layers (CMYK). Black is used as an additional layer due to mixing issues concerning the imperfections of the CMY pigments. With imaging software, an inkjet printer, and some transparencies, physics instructors are just a few keystrokes away from being able to demonstrate subtractive color mixing.