Gamma Test
Find your display's gamma by matching a pattern against a solid grey.
Your gamma
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Step back from the screen and half close your eyes. In one patch the striped half and the solid half will blend into the same shade — that number is roughly your gamma. 2.2 is the standard for almost everything; 1.8 is an old Mac convention. Judge it straight on, because gamma shifts badly with viewing angle on most LCDs.
Your test runs locally in your browser. No device data is uploaded.
How to use the gamma test
Step back from the screen and half close your eyes so the striped half of each patch blurs. In one of them the striped half and the solid half will blend into the same shade — that number is roughly your display's gamma. Go fullscreen for a bigger patch and judge it sitting straight on.
How a web page can measure gamma
A one-pixel checkerboard of pure black and pure white averages to 50% light output no matter what the display's transfer curve does to it, because both extremes are unaffected by gamma. A solid grey patch is affected entirely by it. So the solid value that visually matches the checkerboard tells you the gamma, and your eye does the measuring.
The patterns are drawn pixel for pixel at your display's real resolution. A resampled checkerboard blurs into flat grey and measures nothing, which is why this uses a canvas rather than a CSS pattern.
What to do with the answer
2.2 is the standard for sRGB, Windows, the web and most video, and is what you want unless you have a specific reason otherwise. 1.8 is an old Mac convention. 2.4 is used for video mastering in a fully dark room.
If the answer is far from 2.2, the fix is usually a monitor picture mode or a gamma setting in the on-screen menu, or a display profile in your operating system. Bear in mind that gamma shifts noticeably with viewing angle on most LCDs, so judge it head-on, and that this is an estimate rather than a substitute for a hardware colorimeter.
Frequently asked questions
- How can a web page measure gamma?
- With a trick. A one-pixel checkerboard of pure black and white averages to 50% light output no matter what the display does to it, while a solid grey patch depends entirely on gamma. The solid patch that visually matches the checkerboard tells you the gamma, and your eye does the measuring.
- What gamma should I be aiming for?
- 2.2 for almost everything: it is the standard for sRGB, Windows, the web and most video. 1.8 is an old Mac convention you will rarely want today, and 2.4 is used for video mastering in a dark room.
- Why does the answer change when I move my head?
- Gamma shifts with viewing angle on most LCDs, especially VA and TN panels. Judge it sitting straight on at your normal distance, and expect a different answer from off to one side.
- Is this as good as a colorimeter?
- No. It gives you a usable estimate and will catch a badly wrong setting, but it depends on your eyes, your room lighting and your viewing angle. Proper calibration needs a hardware colorimeter against the panel.