02 Screen test
Backlight bleed & uniformity test
Black and evenly spaced greys, full screen, so light leaking from the edges, blotchy patches and dim corners have nowhere to hide.
Grey level test
Black: Backlight bleed at the edges and IPS glow in the corners.
→ next · ← back · G grid · H hide the label · Esc exit. On a touch screen, tap to change level.
How to check for bleed
Darken the room, set the brightness you normally use and give your eyes a minute. Sit where you usually sit, look at the screen straight on and start with black. Then step up through the greys: problems that hide on black often show at 5–25%, and the 50% grey is where smudgy bands appear. Turn on the grid to compare the corners with the middle.
What you might see
- Backlight bleed: bright patches along an edge that stay put when you move your head. Common on LCDs; OLEDs have no backlight to leak.
- IPS glow: a silvery shine in the corners that changes as you move. It is a property of the panel type, not a fault.
- Clouding: blotches across dark greys, often on large LCD TVs.
- Vignetting and tint: corners darker than the centre, or a colour cast in one area on white.
- Banding: visible stripes in the smooth ramp, where the steps between greys are too coarse.
Judge by eye, not by phone photo: cameras lift shadows and make most screens look worse than they are.
Questions
How much bleed is normal?
Some is normal on most LCDs, especially on a black screen in a dark room. What matters is whether you notice it in films and games at your usual brightness. Makers do not publish a common limit, so a return depends on the seller.
Does backlight bleed get worse over time?
It usually stays much the same. Bleed often comes from pressure on the panel, so check the stand and the frame are not twisted.
Why are there custom grey levels?
Some faults only show at one brightness. Slide the level until a patch is most visible, then compare it with the same spot on other screens.