Follow The Grayscale-Brick Road: Why Color E-Ink Doesn’t Rival Four-Color Printing

On the way to creating its new color product that is supposed to make e-readers “Just Like Paper, Only Better,” E Ink forgot a few basic things. Like elementary school physics. And the color yellow.

As a result, the new Triton Imaging Film has a limited range of colors and a washed-out look that falls far short of four-color printing.

“The color is extremely desaturated even in their carefully presented marketing materials,” writes printing and color expert Gordon Pritchard. “The display's lack of color saturation may actually reveal the cause of the problem.” A friend of Dead Tree Edition who saw a prototype device confirms that the color is underwhelming.

Because they use reflected light (just like paper) rather than emitted light (like computer screens), E Ink’s products seem to be easy on the eyes and on battery life. That has made them a component of such popular products as the Kindle DX and the Barnes & Noble NOOK.

Triton-based readers will shrink “the digital divide between paper and electronic displays,” E Ink promises, thereby “enhancing the visual experience for ePublishing markets such as eBooks, eNewspapers, eMagazines, and eTextbooks."

Here’s the design flaw: Triton uses the red-green-blue (RGB) color scheme that works for computer screens and other emitted-light devices but is ill suited to a reflected-light device.

If you remember your elementary school physics, red light, green light, and blue light can be combined to create just about any color. That works fine if you control the light sources.

But if you use reflected light, you need to filter those primary colors to create the desired hues. That’s why four-color printing relies on cyan (which filters out red light but allows green and blue to be reflected back to the eye), magenta (which blocks out green), and yellow (which filters out blue) – plus black.

“There is no RGB combination of ink hues that will deliver a yellow hue – and yellow is noticeably absent from the images so far shown for this display technology,” Pritchard adds.

If Triton mimicked the CMY (cyan-magenta-yellow) color scheme used by printers, he adds, it would have achieved similar results “in terms of color gamut and saturation. The color intensity would change according to the ambient light and be dependent on the ‘blackness’ and ‘whiteness’ of the underlying black and white screen pigments.”