Black Screen Test
A full black screen shows light that should not be there. On an LCD, look for bleed at the edges and glow in the corners. On any screen, a lit dot on black is a stuck or hot pixel.
One full-screen color. Click, tap or press Esc to end.
How do I check for backlight bleed?
Darken the room first, because bleed is hard to see in daylight. Then work through these steps.
- Turn off the lights and give your eyes a minute to adjust.
- Set brightness to the level you normally use.
- Start the test and look from straight in front, then from a slight angle.
- Note any bright patch and whether it moves when you move your head.
Is it backlight bleed or IPS glow?
Move your head and watch the bright area. Bleed stays put, while glow shifts and changes as your viewing angle changes.
Does an OLED screen have backlight bleed?
No. OLED pixels make their own light and switch fully off, so black should look completely dark. For problems just above black, use the OLED screen test.
How do I show a plain black screen?
Press start above. The page switches to full screen and shows pure black, with no tabs, bars or cursor in the way. Click, tap or press Esc when you are done.
Giving a talk? In a PowerPoint slide show, press B to black out the screen and press it again to come back. To turn the screen off instead, set a short screen timeout in your power settings.
How do I check a laptop or phone for screen bleeding?
Laptop screens are almost always LCDs, so bleed is worth checking on a new one. Open the lid to your usual angle, run the test in a dark room and look along the edges. Bleed that grows when you press the frame or twist the lid comes from pressure on the panel.
On a phone, run the test in the browser at your normal brightness. Many phones now use OLED screens, which cannot bleed. On an Android phone with an LCD, look for a bright band along one edge or a glow in the corners.
Can I reduce backlight bleed?
A little. Lower brightness makes bleed far less visible, and a soft light behind the screen helps your eyes in a dark room. Avoid pressing on the panel, a common online tip, because it can damage the screen.
Does a black screen find every faulty pixel?
No. Black catches pixels that stay lit, but a pixel stuck on one color can hide here. Run the stuck pixel test as well, which cycles through bright colors.
What else is a black screen good for?
It can stand in for a switched off display when you want a dark room without unplugging anything. On an OLED it uses very little power, because black pixels are simply off.
Questions
Should I test at full brightness?
Test at the brightness you actually use. Full brightness makes almost any LCD show some bleed that you would never notice day to day.
How much bleed is too much?
If it shows in dark movie scenes at your normal settings, raise it with the seller. Policies differ by brand, so check before the return window closes.
Why does a photo show more bleed than my eyes?
Phone cameras brighten dark scenes, which makes bleed look far worse. Judge it with your eyes, not a photo.
Does a black screen save power on an LCD?
Very little. An LCD keeps its backlight on behind black, so most of the power is still used. Only OLED screens save real power, because their black pixels are off.