Brightness & Contrast Pattern
Find out whether your monitor is crushing shadow detail or blowing out highlights.
Work in a dimly lit room, straight on to the screen
Click the darkest patch you can still tell apart from the one on its left.
Click the brightest patch you can still tell apart from the one on its left.
How this test works
Two step wedges are drawn: one climbing from pure black in steps of two levels, one falling from pure white the same way. On a correctly set display you can separate almost every step from its neighbour. When the darkest steps merge into a single flat black, the bottom of the range is being clipped before it reaches your eye; when the brightest merge into flat white, the top is. You report the last step you can still distinguish at each end, and the two are judged independently — because they have opposite fixes. Crushed shadows are the brightness control, which on an LCD sets the black level; clipped highlights are contrast, which governs the white end. Telling someone to raise brightness when their whites are clipping would make it worse, so the tool never combines them into one score.
What the results mean
- Darkest step seen
- The lowest level you could still separate from pure black. Below about 8 the shadow end is being clipped.
- Brightest step seen
- The highest level you could still separate from pure white. Above about 247 the highlight end is being clipped.
- Shadow range lost
- How many of the 256 levels are collapsing into black. Every one of them is image detail that cannot be recovered.
- Highlight range lost
- The same at the top of the range, governed by contrast rather than brightness.
Common problems and fixes
- Both ends are clipping at once
- That is characteristic of contrast set too high rather than brightness, because contrast stretches the middle of the range at the expense of both extremes. Lower contrast first.
- I cannot see any of the dark steps
- Check the room before the monitor. In daylight the first several steps are invisible on every display. If it persists in the dark, raise brightness — on an LCD that control sets black level.
- It looked fine yesterday
- Adaptive or ambient brightness will have moved it. So will a dynamic contrast mode, which re-maps the range per frame and clips by design.
Frequently asked questions
Why does raising brightness fix crushed blacks on an LCD?
Because on an LCD the brightness control sets the backlight and black level rather than the white point — it is closer to what a TV calls 'black level' than to what the name suggests. Lowering it pushes the bottom of the range below what the panel can show.
What is limited range and why does it crush both ends?
Some graphics drivers output video-range levels 16–235 instead of the full 0–255. If the display expects full range, everything below 16 and above 235 is clipped before the panel gets it, and both ends of this test fail at once. It is a driver setting, not a monitor fault.
Should I be able to see every single step?
Not necessarily. The bottom one or two steps are below the contrast ratio of many panels even when set correctly. Losing four or more at either end is the point at which it is worth adjusting something.
More in Device
- Gamma Calibration ChartEstimate your display's gamma by matching a grey patch against a 50% dither pattern.
- Black Screen TestFill the screen with pure black to find stuck pixels, backlight bleed and cloudy patches.
- Colour Banding / Gradient TestSee whether your display renders a gradient smoothly or breaks it into visible bands.