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. Five bars just above black and five just below white show which. You say the first you can see; the verdict says what to change.
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.
What it measures
Measured here, not assumed.
- Near black
- Bars at 1, 2, 4, 8 and 16 steps above black on a black ground. A good screen in a dim room shows the first or second.
- Near white
- Bars at 1, 3, 7, 15 and 31 steps below white on a white ground. The same standard.
- The verdict
- Crushed, clipped, both, or the whole range shown, with the setting to change in each case.
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: 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 pattern of bars just above black. If you cannot see the first few, the screen is crushing dark detail to black, usually from brightness set too low or a black level mismatch.
- 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 bars 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.
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