One Flat Colour, and the Screen Becomes the Subject
Fill the display with white, then with black, and the panel can no longer hide behind the picture.
A photograph gives the eye somewhere to go. A flat colour gives it nothing, so attention slides down to the surface itself: a fingerprint near the lower left, corners sitting half a stop brighter than the middle, a faint vertical band that only appears over grey. None of it grew there overnight. It was under the forest and the coastline the whole time.
White is the developer for dust and uneven backlight, since IPS panels tend to lift at the corners. Mid-grey is where the softer faults show up, the mottling reviewers call dirty-screen effect. Black belongs to single pixels: a subpixel stuck on reads as one red, green or blue dot, and on a 27-inch 1440p panel a pixel is about 0.23 mm across, small enough that you find it by moving your head rather than by staring. Clean the glass first, or the evening goes into diagnosing a smudge.
Most of what turns up is a tolerance rather than a fault. Makers allow a few stuck pixels before a panel counts as defective, and corner glow is a property of the backlight, not an accident. Knowing where yours live has a quiet use: you stop mistaking them for specks on a photograph. The flat fill also holds up as wallpaper for a few days, with the icons resting on nothing in particular.
