Gamma test
Sit back and squint slightly. In each column, the solid square sits on a striped background that averages exactly 50% light. The column where the square blends in best is your display's gamma.
Keep browser zoom at 100%. If the stripes look like moiré or you can see individual lines clearly, step back further. The per-channel view shows whether one colour's gamma is off, which appears as a tint in shadows.
Reading the result
- Blends at 2.2: on target for web and Windows content.
- Blends at 1.8–2.0: image looks washed out, shadows too bright. Try a higher gamma setting in the monitor menu.
- Blends at 2.4–2.6: image looks contrasty, shadow detail crushed. Try a lower setting, or check the black level test for an RGB range mismatch.
This checks the whole path after your OS colour profile. If you've loaded an ICC profile or run a calibration, the result reflects that correction too.
What gamma actually is
Pixel values aren't proportional to light. A value of 128 out of 255 is not half as bright as 255; at gamma 2.2 it's about 22% as bright. That curve spends more of the 256 levels on dark tones, where our eyes notice small differences. Drag the gamma to see the curve and what value produces half the light.
Half the light of white takes a pixel value of 186, not 128.
Horizontal axis: pixel value (0–255). Vertical: light output. Dashed: a linear response for comparison.
A display at gamma 2.2 shows a 50% grey signal at only about 22% of full brightness, because your eyes judge brightness non-linearly. Brightness is rarely proportional in the sky either: a half Moon gives only about a tenth of full-Moon light. ahaboo narrates why the Moon has phases at all.
Questions people ask
What gamma should my monitor be?
For the web, Windows and most SDR content, the target is about 2.2 (sRGB uses a piecewise curve close to 2.2). Film and TV mastering often uses BT.1886, roughly 2.4, for dark-room viewing. macOS also targets 2.2 for most content.
How does the checkerboard gamma test work?
A pattern of alternating black and white pixel lines emits, on average, exactly half the light of full white. Your eye blurs it into a mid-grey. The solid grey square that matches it tells you which pixel value your display maps to 50% brightness, and from that the gamma.
Why does the chart look different when I scroll or zoom?
The line pattern must line up with physical pixels. Browser zoom or OS display scaling can blur the lines and spoil the result. This page draws the pattern at device pixels to avoid that; keep browser zoom at 100%.
Can I fix gamma without a colorimeter?
Many monitors have a gamma setting (often labelled 1.8/2.0/2.2/2.4 or as modes). Choose the one where the chart reads 2.2. Beyond that, OS tools such as Windows Display Color Calibration or macOS Display Calibrator Assistant adjust it roughly by eye.