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About this tool
On-screen gamma match, step wedge, banding ramp and clipping patches to sanity-check a display's tone response.
This test pattern measures a display's gamma by exploiting the fact that a one-pixel black and white dither emits exactly 50% of the panel's peak light. Match the striped block to a solid grey and the tool inverts V = 255 x 0.5^(1/gamma) to report the gamma you are actually looking at, alongside a step wedge, a bit-depth banding ramp and near-black and near-white clipping patches. It is a five-minute sanity check for anyone editing photos, video or UI without a colorimeter to hand.
Open Monitor Gamma Test Pattern on AltFTool — it loads instantly in your browser.
Add your input to the workspace.
Adjust the options until the result looks right.
Copy or download the output and put it to work.
The match point inverts a real transfer function instead of asking you to eyeball a curve.
Gamma match, step wedge, banding ramp and clipping patches, all driven by the same maths.
It reports what the tone curve does; it cannot measure white point, uniformity or absolute nits.
Gamma 2.2 is the standard for web, photo and general desktop work, and matches the sRGB transfer function closely. Video grading in a dim room usually targets gamma 2.4 per ITU-R BT.1886, and older Mac prepress workflows used 1.8.
Alternating one-pixel black and white lines average to half the display's peak light output regardless of gamma, because the eye integrates the light linearly. The solid grey that matches has a code value V where (V/255)^gamma = 0.5, so gamma = ln(0.5) / ln(V/255) — a match at 186 means gamma 2.2, and at about 188 means the sRGB curve.
Scaling resamples the one-pixel stripes, which changes their average brightness and shifts the match point. Set the browser to 100% zoom and view the page on the native resolution of the display you are testing.
No. It measures only the grey tone response and cannot measure white point, absolute luminance in cd/m², panel uniformity or colour accuracy. Treat it as a quick check; a calibrator plus profiling software is still needed for colour-critical work.