Black and white level test. The ends of the range.
A screen set wrong loses the ends of its range: shadow detail becomes solid black, or highlights become solid white. Twenty patches just above black and twenty just below white, one step apart, show which. You say the first you can see in this room's light; the verdict says what it means and what to change.
This check is visual: it draws full-screen colours and test patterns on the screen, and you judge the result by eye, so a screen reader cannot describe it. The list under "What it measures" says in words what each one shows.
One check
- Black and white levels
One check after another, with your progress along the top and a plain verdict on each. Nothing you show the camera or say into the microphone leaves this page.
In short
Black and white level test: the answer first
A black level test shows whether your screen is losing shadow or highlight detail. Twenty patches climb one step at a time above black and twenty below white, and the first step you can see in this room's light gives the verdict.
Reading your result
- Shadows crushed
- If the first visible step is late, raise brightness a step and turn off dynamic contrast; on a TV, match the input's black level to the source.
- Highlights clipped
- If the near-white patches merge, lower contrast a step and leave vivid picture modes.
- The room matters
- A bright room hides the darkest steps on any screen. Run it again with the lights down before changing settings.
What it measures
Measured here, not assumed.
- Near black
- Twenty patches, at 1 to 20 steps above black on a black ground, the ladder Lagom's black level test uses. A screen resolving its deepest blacks shows step 1 or 2 in a dim room.
- Near white
- Twenty patches, at 1 to 20 steps below white on a white ground. The same ladder, for clipping.
- The verdict
- From the first step seen, at our lines: step 1 or 2 is deep blacks resolved; 3 to 5 is a typical LCD; 6 or later is crushed, or the room is too bright to tell. A PLUGE strip (bars at 12, 16 and 20 on a ground of 16, video black) sits under the ladder as a reference for whether the screen treats the signal as full or video range.
If it fails
The usual failures, and what fixes each.
- Dark detail crushed
- Raise brightness a step, turn off dynamic contrast, and on a TV set the input's black level to match the source.
- Bright detail clipped
- Lower contrast a step, and turn off vivid or dynamic picture modes.
- Both
- Reset the picture mode to a standard or cinema preset and adjust from there; the extreme presets do both at once.
Where a browser stops
What it cannot tell you.
- Your eyes are the instrument; a page cannot read a pixel's brightness back. Room light matters, which is why every verdict says in this room's light: test near black in a dim room.
- In HDR mode, tone mapping clips highlights on purpose; test in the mode you use.
- A TV's black level setting (Full or Limited) must match the source; a mismatch crushes or lifts black and no other setting fixes it.
Privacy
Nothing leaves this page.
The camera and microphone are read on this page and stopped as soon as they have been measured. The clip you can play back lives in the browser's memory and is discarded when you leave. The location check discards the position. The internet test sends random bytes to this site and nothing else. The result is stored nowhere unless you ask for it by email, and then only the fact that an email was sent is kept.
Questions
Black and white level test, answered
- What is a black level test?
- A ladder of patches just above black, each a step brighter. The first one you can see says how much shadow detail the screen shows in your room. Missing the first five is crushed black, usually from brightness set too low, a black level mismatch, or a bright room.
- What is black crush?
- Dark shades collapsing into solid black, so shadow detail disappears. It comes from brightness too low, dynamic contrast, or a Full and Limited range mismatch between the source and the screen.
- Why can I see all the dark patches but none of the light ones?
- Contrast is set too high or a vivid mode is on, so the brightest shades are clipped to white. Lower contrast a step and test again.
- Is this the same as a contrast ratio measurement?
- No. Contrast needs a meter. This shows whether the range you have is being used, which settings can change.
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