A plain black screen to spot dust, find pixels that stay lit or keep your display dark without turning it off.
When time is up, full screen closes on its own.
Put a white or warm screen in front of you and turn up the brightness. It lights your face softly, like a ring light.
Black shows dust, white shows smudges. Use both and nothing gets missed.
Cycle through red, green, blue, white and black. A dot that doesn't change color is a dead or stuck pixel.
A soft color at low brightness works as a night light or for reading without turning on a lamp.
To see dust and fingerprints, find pixels that stay lit and check backlight bleed on LCD monitors. It also darkens the screen without turning it off.
On OLED and AMOLED screens, yes, because black pixels are switched off. On LCD screens it barely changes.
Tap the screen or press Esc. On a phone you can also use the back gesture.