Gamma and Black Level Test

Tune brightness and contrast and sanity-check gamma with three classic patterns. The black-level pattern shows twenty nearly black squares, the white-level pattern twenty nearly white ones, and the gamma chart compares 1-pixel black-and-white stripes with solid grey patches so you can see which gamma value your screen matches.

Monitor Tests Runs in your browser

Check Gamma, Black Level and White Level

JavaScript is required. This tool runs in your browser, so please enable JavaScript to use it. The instructions below are still available.

How to Use the Gamma & Black Level Test

Set browser zoom to 100% and choose a Pattern.
Press Full screen and view from your normal distance.
For black level, lower brightness until square 1 almost disappears while square 2 or 3 is still visible.
For white level, lower contrast until square 254 is just distinguishable from the background.
For gamma, squint or step back and find the patch whose solid centre blends with the stripes.

About This Tool

Photographers and video editors preparing a screen for work, gamers adjusting shadow detail, and anyone setting up a new monitor or TV.

Input: Pattern · Output: Full-screen test pattern.

Features and Limitations

Features

Twenty numbered near-black and near-white steps with their exact 8-bit values.
Gamma chart with patches for 1.8, 2.0, 2.2, 2.4 and 2.6 drawn with true 1-pixel stripes.
Drawn at device-pixel resolution and re-drawn on resize and full screen.
Short instructions for each pattern.

Limitations

Visual tests are subjective; use a hardware colorimeter for accurate calibration.
The gamma chart requires 100% zoom and a whole-number device pixel ratio; otherwise the stripes are resampled and the reading is wrong (the page warns you).
Ambient light strongly affects black level; test in the lighting you normally use.
Results are computed in your browser; nothing you enter is sent to a server.

Example

On a well set-up sRGB monitor the patch labelled 2.2 blends best with the stripes, and black-level squares from about 2 upwards are visible in a dim room.

Frequently Asked Questions

What gamma should my monitor have?

Most computer content assumes the sRGB curve, which is close to gamma 2.2. Video mastered for dark rooms often uses 2.4.

Why can't I see square 1 on the black-level pattern?

Value 1 out of 255 is extremely dark; many displays crush it. Seeing squares from 2 or 3 upwards is usually fine. If you can't see 5 or more, raise brightness.

Why do the gamma patches look wrong on my phone?

Phones often use fractional pixel ratios and automatic brightness or tone mapping. Use the test on a desktop monitor at 100% zoom for meaningful results.