Gamma Test

How to check your monitor’s gamma

1. Set browser zoom to 100% and read the note under the pattern buttons. If it reports a scale such as 125% or 150%, the stripes are not whole pixels and the chart is less reliable.
2. Use your usual brightness, sit at your normal distance and press Start test.
3. On Gamma chart, step back or squint until the striped borders blur into flat gray. Find the patch whose solid center blends into its border: its label is your approximate gamma.
4. If the match falls between two patches, read your gamma as between their labels: centers left of your gamma look darker than their borders, and centers to the right look brighter.
5. Use Next, the arrow keys or a tap for the other patterns. On Midtones, the 11 steps should look evenly spaced: a dark middle points to high gamma, a washed-out middle to low gamma.
6. On Shadow detail and Highlight detail, note the first bars you can tell apart from black and from white. For a closer look at the darkest shades, use the black level test.

What is gamma on a monitor?

Gamma is the curve that sets how bright each shade between black and white appears on a screen. At gamma 2.2, the usual target for computer monitors, a gray sent at half the signal gives off only about 22% of white’s light, which looks like a middle gray. Higher gamma darkens the midtones; lower gamma washes them out.

Gamma 2.2 vs 2.4: which should you use?

Use 2.2 for everyday computer use, the web, games and photos. It is close to the sRGB curve that computers and most web content assume. A display that follows sRGB matches at the 2.2 patch or a little past it toward 2.4, because the sRGB curve reaches half of white’s light between levels 187 and 188 of 255, and the 2.2 patch is 186.

Gamma 2.4 is the reference for HD video mastering, set out in ITU-R BT.1886, and suits a dark room. In a lit room it can make shadows look too dark.

How to change gamma

Change one setting at a time and check the chart again after each. The guide to adjusting a monitor by eye puts the steps in order.

• On the monitor: many have a gamma option or an sRGB picture mode in their on-screen menu. Names and values vary by brand.
• On Windows: search Start for Calibrate display color. It walks you through gamma, brightness, contrast and color balance, then saves the result.
• In NVIDIA, AMD or Intel graphics settings: desktop color controls, some with a gamma slider, change the whole screen.
• On a Mac: the color profile options in Displays settings include a calibrator that builds a custom profile.
• In a game or video player: its own gamma or brightness slider changes only that app.

What this test can detect

• Your approximate gamma, from 1.6 to 2.8 in steps of 0.2, from the patch whose center blends into its striped border.
• Midtones that look too dark, from gamma set too high, or washed out, from gamma set too low.
• Shadow and highlight bars that disappear into black or white.
• Display scaling and browser zoom that together do not come to a whole number, reported as a percentage under the pattern buttons.

How it works

Each chart patch has a border of alternating black and white lines, each 1 CSS pixel tall, which average to half of white’s light once your eyes blur them. The solid center is the gray level that a display with the labeled gamma shows at half of white’s light: 165 for 1.6, 186 for 2.2 and 199 for 2.8, out of 255. Where center and border match, your gamma is close to that label.

The page reads the browser’s device pixel ratio when it loads and on every resize, and adds a warning when it is not a whole number. It measures nothing: you judge the match by eye.