How color e-ink works
Last checked September 28, 2026
Electronic ink in one paragraph
Classic E Ink is made of millions of tiny capsules, each about the width of a human hair, holding charged black and white particles in clear fluid. An electric field pulls one color or the other to the surface. Once they’re there, they stay without power: the display is bistable, and only pixels that change need energy. It’s reflective like paper, so it needs no backlight (E Ink).
E Ink Spectra 6: what’s in photo frames
Every color frame on our comparison uses E Ink Spectra 6. Instead of just black and white, each pixel holds colored pigment particles that are moved into place to show one of six colors:
- Black
- White
- Yellow
- Red
- Blue
- Green
E Ink quotes up to 200 pixels per inch, a typical contrast ratio of 30:1, and an operating range of 0-50 °C (E Ink Spectra 6). It was designed first for shop signs and posters, which is why the colors are bold and saturated rather than subtle.
Dithering: how six inks make a photo
A pixel can only be one of the six colors, so every other shade is faked by mixing dots, the same trick newspapers use. The most common method is Floyd-Steinberg error diffusion: take each pixel in turn, pick the nearest of the six colors, work out how far off it was, and push that error onto the pixels to the right and below (7/16 right, 3/16 below-left, 5/16 below, 1/16 below-right). Across an area the dots average out to the right color. Waveshare recommends exactly this method for its Spectra 6 panels (Waveshare manual), and frame makers use their own tuned versions: Aura says its algorithm creates the appearance of millions of tones (MacRumors).
That’s why e-ink photos look grainy up close, like film stock, and smooth from across the room. You can see it happen to your own photo in our photo converter, which runs the same Floyd-Steinberg method in your browser.
Real inks are also duller than pure screen colors. Pimoroni’s open-source driver for its Spectra 6 displays lists measured colors next to the pure ones: its “white” is a light gray (RGB 161, 164, 165) and its blue is a dark navy (61, 59, 94) (Pimoroni inky library). Our converter’s “muted” preview uses those values.
Why a refresh takes so long
Changing the picture means physically moving pigment through fluid, several times over, to get each color right. That’s why frames flash and shimmer for a while: about 20 seconds on Bloomin8, about 30 on Aura Ink, 15-30 on SwitchBot, and up to a minute for InkPoster’s first image. Waveshare quotes 19 seconds for a full refresh of its 13.3-inch Spectra 6 panel. It’s also why frames change photo once a day or less: every refresh uses battery.
Other color e-paper: Kaleido 3 and Gallery 3
| Technology | How it makes color | Where you’ll see it |
|---|---|---|
| Kaleido 3 | A color filter over a black-and-white panel: 4,096 colors at 150 ppi | Color e-readers and notebooks |
| Gallery 3 | Four particles (cyan, magenta, yellow, white) in each pixel, 300 ppi | E-readers and notebooks |
| Spectra 6 | Six colored particles, up to 200 ppi | Signs, shelf labels and art frames |
Source: Good e-Reader (August 25, 2026). Kaleido colors are more muted because the filter sits over a grayscale panel; photo frames use Spectra 6 instead.