Why test with a grey screen?
Mid grey is the best colour for spotting problems that white and black hide. Because the panel is neither fully on nor fully off, small differences in brightness and colour across the screen become visible.
- Uniformity. A good screen shows the same grey everywhere. Darker corners, brighter edges or a tinted patch mean uneven backlighting.
- Dirty screen effect. On TVs and large monitors, faint blotches or vertical bands that seem to "stick" to the screen as the picture moves are easiest to see on grey.
- Banding and tint. Grey should look neutral. A pink or green cast suggests a colour balance problem.
- A neutral background. Photographers and designers use grey as a calm, colour-neutral backdrop.
How to test your screen
- Darken the room and set your display to its normal picture mode.
- Press Start grey screen and look at the whole screen from your usual viewing distance.
- Try a darker grey (around 20%) and a lighter one (around 70%) with the colour picker, as different problems appear at different levels.
Some variation is normal, especially on large LCD panels. If patches are obvious in everyday use, such as sports with lots of sky or grass, contact the seller while you can still return it.
Grey as a neutral background
Designers and photographers use mid grey as a reference because it has no colour of its own. When editing photos, a grey surround stops bright or coloured backgrounds from fooling your eyes about brightness and colour. For product photography, a tablet showing grey can act as a small neutral backdrop that won't add a colour cast. It is also handy for checking glasses and lenses for smudges, as marks show clearly against an even mid-tone. If you are judging colour, set your screen to its standard or sRGB picture mode, switch off any blue-light filter and let the screen warm up for a few minutes before you look closely.