Explainer
A test you cannot read is just a colourful screen
Five full-screen patterns will tell you more about an external display than any spec sheet. The catch is that a pattern only means something if you know what you are looking at.
What is worth testing
- Dead and stuck pixels — single points that stay dark or stay lit against solid fields.
- Grayscale — whether the panel steps smoothly between tones, or banding appears where the ramp should be continuous.
- Uniformity — a flat mid-grey field makes backlight bleed, clouding and a dirty-screen effect visible in a way that a photograph never does.
- Sharpness — whether the panel is actually running at its native resolution and whether scaling is blurring fine structures.
- Motion — how much the panel smears a moving edge. This is where cheap panels differ most and where advertising numbers mislead most.
Every pattern needs one readable sentence
A pattern without an instruction is a coloured screen. Each test should say, in one sentence, what you are watching and what a healthy panel looks like. If the sentence is missing, the user learns nothing except that something was displayed.
Why a bordered overlay beats a full-screen Space
The obvious way to show a full-screen pattern is to enter a native full-screen Space. The problem is that a Space is restorable state: a test tool that leaves one behind is the classic way to strand a user in a window they cannot get out of. A borderless overlay pinned to the target screen closes back to the desktop exactly as it was.
The Esc key does not just work
Borderless windows refuse key status unless you explicitly ask for it. Without that, Esc never reaches the running test and the only way out is to force-quit an app that has covered the screen. If a test tool could trap you, it is not a test tool.
Honest limits
- These tests show you what your eyes can notice. They are not a colorimeter: uniformity and grayscale tests reveal problems, they do not measure them.
- Seeing nothing is not proof of a good panel. It means no defect crossed your threshold, on that field, at that brightness.
- Motion is the least conclusive of the five — smear depends on the camera you compare against, and no full-screen pattern replaces a high-speed capture.