Display mid grey in fullscreen, then white and black in a darkened room. Scan across the panel and note corners or patches that look brighter, darker, or warmer than the rest.
Uniformity issues rarely appear in everyday apps. A flat field is the reliable way to judge backlight evenness and corner glow.
What to look for
- Vignetting — edges darker than the center (common on IPS desktop panels)
- Backlight bleed — cloudy glow near corners on black (often laptops)
- Color shift — whites look yellow in one zone and cool in another
- Banding — visible steps in smooth gradients instead of a continuous fade
Best test colors
Mid grey (start here)
Fifty-percent grey balances highlight and shadow detail and is the usual quick check for uneven backlight. Open the grey screen tool fullscreen and trace an S-pattern with your eyes — center, corners, then edges.
White (backlight stress)
Full white drives the backlight hardest. Large monitors may show a brighter center or dimmer corners here even when grey looked acceptable.
Black (bleed and leak)
Turn off overhead lights. Black fullscreen reveals light around laptop hinges and pressure spots from case flex.
Six-step uniformity routine
- Set brightness to roughly 50–70% — maximum brightness can hide mild unevenness.
- Disable dynamic contrast and aggressive local dimming in the monitor menu.
- Open grey fullscreen for about 60 seconds.
- Repeat on white and black.
- On laptops, tilt the lid slightly — some bleed only appears at certain angles.
- Decide whether flaws appear in normal content or only on test patterns.
Banding vs panel defects
Vertical bands on a brightness ramp may come from GPU settings, cable quality, or the panel itself. Gradient tools in display tests help separate banding from random clouding.
Is it return-worthy?
Mild corner shading on IPS panels is often within tolerance. Support teams usually care when:
- The uneven area is obvious in normal content
- One region has a strong color cast on neutral grey
- Bleed covers more than a small corner in dark scenes
Photograph the test color fullscreen with room lights off.
See also: Best colors for pixel tests · Fullscreen color test guide
