Background
What display gamma is and how the stripe test works
Gamma describes how a display turns signal values into brightness. Brightness does not rise in a straight line with the signal. It follows a curve, and gamma is the number that describes the shape of that curve. It decides how bright the mid-tones look. Too high and shadows sink into black; too low and the image looks washed out and flat.
Why screens use a gamma curve
Human vision is much more sensitive to differences between dark tones than between bright ones. Encoding images with a gamma curve spends more of the available code values on dark tones, where we would otherwise see banding. The display then applies the opposite curve so the image looks right.
Most computer images and web content are made for the sRGB standard. Its transfer curve is close to gamma 2.2. Video mastered for dim rooms uses BT.1886, which behaves like gamma 2.4. Older Macs used 1.8 until Mac OS X 10.6 (Snow Leopard) moved to 2.2 in 2009.
How the stripe-and-patch comparison works
A pattern of alternating black and white lines, one pixel each, averages out to exactly half of full brightness when you step back and your eye blends the lines. That is a physical fact that does not depend on gamma. The solid patches next to it are drawn with gray values chosen so that each patch would also show half brightness at one specific gamma.
The patch value for gamma γ is 255 × 0.5^(1/γ). For gamma 2.2 that gives 186, for 1.8 it gives 174, and for 2.4 it gives 191. The patch that blends best with the striped area tells you which gamma your display is closest to at that brightness.
| Gamma | Gray value (0–255) | Typical use |
|---|---|---|
| 1.8 | 174 | Legacy Mac, some print workflows |
| 2.0 | 180 | Intermediate preset on some monitors |
| 2.2 | 186 | sRGB, web, Windows and macOS desktop |
| 2.4 | 191 | BT.1886 video in a dim room |
| 2.6 | 195 | DCI digital cinema |
Getting a reliable reading
- Use 100% browser zoom and 100% OS scaling, or a scale that maps the stripes to whole device pixels. Scaling blurs the stripes into gray and breaks the comparison.
- Sit back far enough that you cannot see individual lines, or squint slightly.
- Look straight at the area. TN panels in particular change gamma strongly when viewed from above or below.
- Check each color channel separately if the gray result looks tinted. A different match per channel points to a color balance problem.
Changing gamma
Many monitors have a Gamma setting in the on-screen menu, sometimes with values like 1.8, 2.0, 2.2, 2.4, or labels like Mode 1–3. Picture presets such as Game or Cinema often change gamma too, so check which preset is active. Graphics drivers offer gamma sliders, but they work by changing the signal and can cause banding. For accurate results, a hardware calibration with a colorimeter is the reliable route.
Common questions
- Which gamma should I choose?
- For general computer use and web content, 2.2 is the standard target. For watching video in a dark room, 2.4 is common. Whatever you choose, keep it consistent with what the content was made for.
- Why does the result change with brightness?
- Many displays do not follow a perfect gamma curve. They are a little off at different points of the curve, and dynamic contrast or eco modes can change the curve with content. Test at the settings you normally use.
- Is gamma the same as brightness?
- No. The brightness control on most monitors changes the backlight, which raises or lowers the whole image. Gamma changes the mid-tones while leaving pure black and pure white where they are.