Uniformity test
Flat grey fields at several brightness levels. A perfect panel looks like one even sheet; real ones show darker corners, blotches or faint bands. Here's how to read yours.
How to judge uniformity
- Compare zones. Turn on the 3×3 grid and compare each cell to the centre. Corners 10–20% darker than the centre is common on LCDs.
- Look for tint shifts: one side slightly pink or green on grey. Mild tint differences are common; strong ones on a new panel are worth raising with the seller.
- Pan your eyes across the 20–30% greys to see dirty screen effect: blotches that stay fixed to the screen while your eyes move.
- OLED: check 5% and 10% for faint vertical bands or a darker strip. Some near-black unevenness is inherent to current OLED panels.
Measured uniformity (reviewers report a percentage deviation per zone) requires a colorimeter. Our eyes are good at spotting blotches and poor at judging absolute brightness, so trust patterns over impressions of "the left side seems darker".
Questions people ask
What is the dirty screen effect?
Dirty screen effect (DSE) is blotchy or banded unevenness that looks like a smudge on the screen, most visible when a mid-grey or a flat coloured surface pans across the display, such as ice or grass in sports.
What is vignetting?
Darker corners or edges compared with the centre. It is common on LCDs, especially edge-lit ones, and small amounts are normal.
Why are OLEDs tested at 5% grey?
OLED unevenness, such as faint vertical bands or a tinted patch, is most visible at very low grey levels just above black. That is why reviewers look at 1–5% grey slides for OLED.