What is monitor uniformity?
Uniformity is how consistent brightness and colour are across the panel. A perfectly uniform display would emit the same luminance (measured in cd/m², also called nits) and the same colour temperature in every region. In practice no panel is perfect — edge-lit LCDs are dimmer in corners than centre, VA panels show vignetting, and even OLED can have minor brightness gradients. The 3×3 grid here lets you compare nine zones side-by-side. Variations under 10% are imperceptible; over 20% are a defect.
What is backlight bleed and how do I spot it?
Backlight bleed is light leaking from the LED edge backlight past the LCD layer, visible as bright patches (usually in the corners) on a black screen. Display the black or 25% grey patch fullscreen in a dark room. Patches of yellow-white light along the edges or corners are bleed. Some bleed is normal on edge-lit IPS; severe, cloudy patches across half the screen are warranty-replaceable. OLED panels have zero bleed because each pixel emits its own light.
What's the difference between backlight bleed and IPS glow?
IPS glow is a viewing-angle artifact — the corner you look at off-axis appears to glow with a silvery-white sheen. It moves as you move your head; bleed stays put. IPS glow is inherent to the panel technology and not a defect — every IPS monitor shows it to some degree. You can reduce it by sitting further back, lowering brightness, and viewing in a dimmer room. VA panels show no IPS glow but have stronger off-axis colour shift instead. OLED has neither.
Why do the grey patches reveal more than the white?
Backlight irregularities are most visible at low-to-mid luminance because the eye's contrast sensitivity peaks there. On pure white, a 10% drop is hard to see; on 25% grey, the same 10% drop is obvious. Use white to check for dust or panel scratches, 50% grey for general uniformity, 25% grey for bleed, and primaries (red, green, blue) for colour-temperature drift — corners on cheap monitors often skew noticeably cooler or warmer than centre.
What does a professional uniformity spec look like?
Manufacturers like Eizo, NEC, and ASUS ProArt quote 'delta-L uniformity' — usually ≤5% variation across the panel, and 'delta-E ≤3' for colour. Consumer monitors are typically 10–15% delta-L. The DisplayHDR 600 spec requires a maximum 2:1 luminance ratio between any two 5%-of-screen regions. To measure precisely you need a colorimeter (i1Display Pro, Calibrite Display) and software like DisplayCAL. Visual inspection here catches gross defects but won't quantify them.
Can I fix poor uniformity?
Mostly no — uniformity is set by the backlight layout and panel quality, both fixed at manufacture. Some professional monitors include a 'Uniformity Compensation' OSD setting that uses a factory-measured correction map to even out the field; this costs peak brightness and contrast but improves consistency. For everyday users: lower brightness reduces visible bleed, and slight off-axis variation is normal. If a single quadrant is grossly different, claim warranty. See /monitor/dead-pixel for stuck-pixel checks and /monitor/gamma for tone-response checks.