How to run a backlight bleed test
- Turn off the lights or close the curtains. Bleed is hard to see in a bright room.
- Set the monitor to the brightness you normally use. Testing at maximum brightness makes any bleed look stronger than it does in daily use.
- Click Full screen. The hint and the cursor fade after a moment.
- Give your eyes a few seconds to adjust to the dark.
- Sit where you normally sit and look straight at the center of the screen. Check the edges and corners for patches of light.
- Move your head left, right, up and down. A glow that shifts is IPS glow. A patch that stays put is backlight bleed.
- Step through the dark grays with → or a click. Some problems, such as clouding, show up better on gray than on pure black.
Backlight bleed, IPS glow and clouding
| Effect | What it looks like | Changes with your angle? | Screens affected |
|---|---|---|---|
| Backlight bleed | Bright patches along the edges or in the corners | No, it stays in place | LCD screens (IPS, VA and TN) |
| IPS glow | A silvery or warm glow, often strongest in the corners | Yes, it shifts and fades as you move | IPS screens |
| Clouding | Blotchy, uneven patches across the screen | No | LCD screens |
| None of these | An evenly dark screen | No | OLED screens, which have no backlight |
How the test works
An LCD screen has a backlight that stays on behind the whole panel. To show black, the liquid crystal layer blocks that light, but it can't block all of it. Where the panel and frame don't sit perfectly evenly, extra light escapes, usually near the edges. A full screen of pure black (#000000) is the color that makes this leak most visible.
The gray steps set each color channel to 5%, 10% and 20% of its maximum value (#0D0D0D,#1A1A1A and #333333). They help on monitors with local dimming, which can switch zones of the backlight off on a pure black screen and hide bleed. They also make clouding and uneven dark grays easier to see. Full screen mode uses your browser's Fullscreen API, and nothing is uploaded.
How to make bleed and glow less visible
- Lower the brightness. Bleed and glow both scale with the backlight.
- Add a little light behind or around the monitor, so your eyes aren't adjusted to total darkness.
- Sit a bit farther back and centered. IPS glow depends on your viewing angle.
- If your monitor has local dimming, try turning it on for dark content.
- On a new monitor, decide within the store's return window. Bleed doesn't improve with software.
While you're testing, run the dead pixel test too, check brightness evenness on a full white screen, and confirm your refresh rate with theFPS test.