Black and white level test

How to run the test

1. Let the screen warm up for a few minutes and use the picture mode you normally use.
2. Dim the room lights; reflections hide the darkest patches.
3. Choose Black level (1–20) and press Full screen. Each patch shows its RGB value (0–255) in faint text.
4. Count the patches you can tell apart from the black background, looking straight at the screen from your usual distance.
5. Switch to White level (235–254) and count the patches you can tell apart from the white background.

Reading the result

• Low black patches merge with the background: black crush. Shadow detail in films and games will be lost. Brightness may be set too low, or a dynamic contrast, black stabiliser or gamma setting is darkening the shadows.
• The black background itself looks grey and every patch is easy to see: blacks are raised, often because brightness is set too high.
• Patches up to about 16 all disappear, or the black looks washed out on a TV or monitor connected by HDMI: the computer and the screen may disagree on the RGB range (full versus limited). Check that the graphics driver's output range and the screen's black level or HDMI range setting match.
• High white patches merge with the white: white clipping. Contrast may be too high, or a vivid picture mode is boosting highlights.

Adjust brightness for the black patches and contrast for the white patches, one setting at a time, and run the test again after each change.

Limits

• How many patches you can see depends on the panel, the room light and your viewing angle. There is no fixed number every screen must show; aim for as many as you can see without the black background turning grey.
• Operating-system colour management, night-light or blue-light filters and HDR modes change what reaches the screen. Turn them off for the test, or test with the settings you actually use.
• This is a visual check, not a calibration. It does not measure luminance in nits or HDR performance; that needs a colorimeter.

For banding across the whole tonal range, use the gradient test; for patches and clouding on flat greys, the monitor uniformity test; for a plain field, the black screen.