Why an e-ink page needs a reset
Many e-readers use electrophoretic displays, often called e-ink. Each tiny screen area contains charged pigment particles that move when the device applies an electric field. Their positions create the dark letters and light background. Unlike a phone screen, this kind of display can keep showing an image without continuously using power to redraw it.
But changing one page into another is not always perfectly clean. Some particles may not settle exactly where intended, leaving a faint remnant of the old text—a visual effect called ghosting. After several page turns, those traces can become more noticeable against the new page.
The flash is part of the cleanup
To clear the residue, the reader can run a fuller refresh: it drives the display through a sequence of states before forming the next page. That sequence makes the whole screen briefly appear to invert or go dark, then return with the new text. The flash is not the screen turning off; it is the visible cost of repositioning the display’s pigment particles.
A device may skip that full reset on some page turns to make reading feel smoother. A later refresh can then clear the accumulated traces. The tradeoff is straightforward: fewer flashes mean quicker-looking transitions, while a more thorough refresh helps keep the page crisp.
