From Eye to iPad: The Technology Behind Paper

FastCompany has a profile of the iPad app Paper (by FiftyThree) and the technology behind it:

What vaulted FiftyThree over a hot pile of math was a major insight gleaned from two dead German scientists named Paul Kubelka and Franz Munk. In 1931, they published a paper called Ein Beitrag zur Optik der Farbanstriche, or “a contribution to the optics of paints,” which showed that this color-space question predated computing by several decades. The paper laid out a “theory of reflectance” with an equation which could model color blending on the physical experience you have with the naked eye. That is, how light is reflected or absorbed by various colors.

Today, computers store color as three values: one for red, green and blue, also known as RGB channels. But the Kubelka-Munk model had at least six values for each color, including reflection and absorption values for each of the RGB colors. “While the appearance of a color on a screen can be described in three dimensions, the blending of color actually is happening in a six dimensional space,” explains Georg Petschnigg, FiftyThree’s cofounder and CEO. The Kubelka-Munk paper had allowed the team to translate an aesthetic problem into a mathematical framework.

 Moving from a three-dimensional color-space to six dimensions was the difference between old drab color-mixing and absolute realism. “What creates the shades you see between paints is this interplay of absorption and reflection,” says Petschnigg. “Compare red nail polish to red ink: both are red, but the nail polish will be visible on black paper because it reflects light. The ink won’t be, because it absorbs light.”

Paper is one of the most beautiful apps on the iPad. I highly recommend getting it (the basic version is free) if you don’t have it.

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