In this series, we’ll take a deep dive into the color rendering capabilities of E Ink Spectra™ 6 (E6). This first part focuses on understanding the fundamental color gamut and its limitations.

Understanding E6’s Color Gamut

E Ink Spectra 6 is built on a six-color particle system: black, white, red, yellow, blue, and green. However, the actual color gamut is far more complex than simply having six colors.

The Discrete Color Space

Unlike traditional displays that can produce millions of colors through RGB subpixels, E6 operates in a discrete color space. Each pixel can only display one of the six base colors at a time. This fundamental limitation means:

  • No color mixing at the pixel level: Each pixel is either black, white, red, yellow, blue, or green—nothing in between
  • Limited color transitions: Smooth gradients are challenging to achieve
  • Dithering required: To create intermediate colors, spatial dithering must be used

Color Accuracy and Saturation

The base colors in E6 are not ideal RGB values. For example:

  • Red: Instead of pure (255, 0, 0), E6’s red might be closer to (180, 40, 30)
  • Brightness: Colors appear dimmer than their ideal counterparts
  • Saturation: Colors are less saturated than what we might expect

This means that even the “pure” colors in E6 are compromises between brightness, saturation, and the physical limitations of the ePaper technology.

The Challenge of Color Coverage

One of the most significant challenges with E6 is covering the full range of colors that appear in real-world images, especially:

  1. High-luminance colors: Bright colors that require high brightness values
  2. High-saturation colors: Pure, vibrant colors that need high saturation
  3. Magenta and Cyan: Colors that don’t map directly to any of E6’s six base colors

In the next part of this series, we’ll explore how these limitations affect real-world image rendering and what techniques can be used to work around them.