Screen Uniformity Test
A solid grey field makes uneven brightness, backlight bleed, and clouding far easier to spot than on white or black alone. Drag the slider to try several grey levels — defects often show up more clearly at specific brightness points.
Why Grey, Not White?
Pure white can wash out subtle brightness differences. Mid-grey sits in the range where the human eye is most sensitive to small luminance variations, making unevenness stand out.
Backlight Bleed vs. Clouding
Bleed usually appears as brighter patches near the screen edges or corners. Clouding looks like soft, uneven grey blotches across the middle of the panel — both are more visible in a dim room.
Try Multiple Levels
Some panel defects only show at low brightness, others only near full brightness. Sweep the slider from 10% to 90% rather than checking a single grey value.
When to Worry
A little edge glow is normal on most LCD panels. Large, distinct bright patches or dark blotches — especially on a new monitor — are worth raising with the manufacturer or retailer.
Keyboard Shortcuts
| F | Press F on any tool page to enter fullscreen and hide all browser chrome. |
| Esc | Exit fullscreen or move your mouse to reveal the floating toolbar. |
| ↑ / ↓ | Increase / decrease grey level by 5% |