Grey screen, full screen and free

A flat 50 percent #808080 field, which is what reviewers actually use to judge a panel.

Escape or one tap comes back.

Every colour, one tap away

Brightness, timer and colour cycle

The screen professionals actually use

Ask anyone who reviews monitors for a living which single colour tells them most about a panel and the answer is mid grey, not white and not black. The eye compares mid tones far more accurately than it compares extremes: white saturates your vision and hides subtle differences, black gives it nothing to work with, and 50 percent grey sits exactly where human contrast discrimination is best.

That is why uniformity measurements, dirty screen effect tests and tint checks are all done on grey. A panel that looks flawless on white can look visibly blotchy on grey, and the blotchy version is the one you will notice while reading a document.

What to look for

  • Patches that read warmer or cooler than the rest of the field. That is tinting, and it is the most common uniformity fault on large panels.
  • A dirty, mottled texture across the whole screen, most visible when you move your eyes across it. That is dirty screen effect, and it is what makes panning shots in sport look smeary on a television.
  • A gradual falloff in brightness from the centre towards the corners. Some is normal on every panel. A lot is a backlight problem.
  • Vertical or horizontal banding, which usually shows at grey and nowhere else.

Grey as a work surface

Photographers and retouchers work against mid grey rather than white or black for the same reason galleries paint their walls grey: a neutral mid tone does not bias your perception of the colours you are judging. If you are editing images and your application lets you choose a canvas background, a value near this one is the correct choice, and a second monitor showing this page makes a serviceable neutral surround.

Checking that grey is really neutral

A correctly calibrated display shows #808080 as a colourless grey with no visible tint at all. If it looks warm, cool, green or pink to you, and it looks that way across the whole panel rather than in patches, your white balance is off rather than your panel being faulty. Most monitors have a colour temperature setting with a 6500K option, which is the right starting point.

Frequently asked questions

Why do reviewers test uniformity on grey instead of white?

Because human contrast discrimination is best in the mid tones. White saturates your vision and hides small differences, black gives the eye nothing to work with, and 50 percent grey sits exactly where you can see the least difference. A panel that looks flawless on white can look visibly blotchy on grey.

What is dirty screen effect?

A mottled, grubby looking texture across a flat field, most obvious when you move your eyes across it or when the camera pans in a sports broadcast. It is a uniformity fault in the panel and it shows on grey far more clearly than on any other colour.

My grey looks warm or cool rather than neutral. Is that a fault?

If the whole panel is tinted rather than patches of it, that is white balance rather than a defect. Most monitors have a colour temperature setting with a 6500K option, which is the right starting point. Tinting that varies across the panel is a uniformity fault and is not adjustable.