Panel uniformity
Also called screen uniformity · dirty screen effect · DSE
Uniformity is how evenly a screen shows a single flat color from edge to edge. Poor uniformity shows as darker corners, tinted areas or faint banding on a plain gray.
In practice
Uniformity problems are most noticeable when the screen shows a large flat area: a gray document background, a sky in a game or a solid color in design work. They show as darker edges, a warmer tint on one side or faint vertical bands. Some variation is normal. Large differences matter most for photo and design work.
How to check
Show full screen gray in the dead pixel test at your normal brightness and look across the whole screen. Then try a darker gray if your monitor menu allows it. Note any patches or bands and whether they stay in place. Uniformity is set at the factory, so it rarely improves and is best judged during the return window.