Grayscale test
A precisely drawn greyscale ramp and step wedge, for finding crushed blacks, clipped whites, banding and tint shifts in neutral tones.
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The ramp is drawn one column at a time at exact sRGB code values, with no browser gradient and no dithering, so anything you see in it comes from your display chain.
How to run this test
- Start on the continuous ramp and go full screen. Give your eyes a moment to settle.
- Run your eye from black to white. The change should be smooth, with no visible steps and no point where the tone stops changing.
- Switch to the 32-step wedge. You should be able to distinguish every adjacent pair of patches, including the darkest two and the lightest two.
- Switch the channel to red, then green, then blue. A neutral ramp that drifts towards one colour tells you the channels are not tracking each other.
- If the darkest patches merge, go to the black level test, which isolates that problem and explains the usual causes.
What a problem looks like
- Crushed blacks
- The darkest few patches all look identical. Shadow detail is being thrown away, usually by a brightness setting that is too low, a contrast setting that is too high, or a limited-versus-full RGB range mismatch between your computer and your display.
- Clipped whites
- The lightest few patches merge into one flat white. Highlight detail is being lost, most often because contrast is set too high or because a vivid picture mode is pushing the top of the range.
- Banding in the ramp
- Visible steps in what should be a smooth gradient. This is drawn one column at a time at exact values, so any stepping came from the display chain: panel bit depth, a colour management step, or a driver setting.
- A tint that changes along the ramp
- Neutral greys that go slightly green in the midtones and slightly blue in the highlights, for example. This is greyscale tracking, and it is what calibration actually corrects. It is extremely common and usually invisible until you look at a ramp.
- Posterisation on one channel only
- If the red ramp bands and the green one does not, the problem is more likely in the signal path or a colour setting than in the panel itself. Check your cable and your GPU output settings.
What to do next
If something looks wrong, check it again in a normally lit room and from straight on, then check whether it appears on a second device. If it only happens on this screen and you are still inside the return window, that is the time to contact the retailer.
Questions people actually ask
Why draw the ramp on a canvas instead of using a CSS gradient?
Because browsers may dither a CSS gradient, and dithering hides exactly the banding this test exists to reveal. Drawing one column at a time at explicit code values means what you see came from your display chain, not from the rendering engine.
Does visible banding mean my monitor is 6-bit?
Not necessarily, and this test cannot tell you the panel bit depth. GPU dithering, video driver settings, colour management and the cable all affect what reaches the panel, and 8-bit with frame rate control is visually indistinguishable from native 10-bit here. Banding is a symptom with several possible causes.
How many steps should I be able to see?
On a well set-up display you should distinguish every patch in the 32-step wedge and most of the 64-step one. If several adjacent patches at either end merge, that end of the range is being clipped, which is a settings problem far more often than a panel problem.
My greys look slightly blue. Is that a fault?
Probably not a fault. Many displays ship with a cool white point because it looks brighter in a showroom. Check your colour temperature preset and your OS colour profile first. Correcting it properly across the whole range is what a calibrator does.