Check a monitor's screen before you buy, sell or worry

Look across the whole screen on each colour from about 50 cm, then closer along the edges and corners.

• Dead pixel: a dot that stays dark on the white screen.
• Stuck pixel: a dot that stays red, green or blue. It stands out on black and on the colours it does not belong to.
• Line: a thin line across the whole screen points to a panel or cable fault, which is more serious than one pixel.
• Dust or a pixel? Dust looks soft and moves with your viewing angle; a pixel fault is a sharp square that stays put.

Use the black screen in a dim room at your normal brightness, not at maximum. Look from straight in front, then move your head a little.

• Bleed: bright patches along an edge or in a corner that stay in place when you move your head.
• Glow: a haze that shifts or grows as your viewing angle changes. Some glow is normal for LCD panels, especially IPS; VA panels usually show less.
• Clouding: blotchy lighter areas across the black.

Mid and dark greys reveal differences that white and black hide.

• Uneven brightness: a corner or band that is clearly darker than the centre. A slight fall-off towards the edges is normal.
• Tint patches: areas that look pinkish, yellowish or greenish compared with the rest.
• Pressure marks and smudges: ripples, spots or a dirty-looking patch that is not on the glass.
• Image retention: a faint ghost of a taskbar or window. On LCDs it normally fades within minutes.

Each ramp has all 256 levels from dark to bright. It should look smooth.

• Banding: visible steps or stripes in a ramp.
• Colour cast: the grey ramp turning greenish or pinkish in places.
• Not always the panel: graphics-card colour settings, a non-native mode or a cheap cable adapter can cause banding too. If in doubt, compare with another monitor on the same computer.

These patterns are drawn one panel pixel at a time, whatever the Windows scaling. At the native resolution they look like flat, even grey from a normal distance and a crisp fine grid close up.

• Waves, stripes or blur mean the picture is being scaled: check the resolution above, the browser zoom, or the monitor's sharpness setting.
• Text: the last screen shows text at several sizes. Small text should be readable without colour fringes.
• Pixel density: a 27-inch Full HD screen has about 82 pixels per inch, so text is softer than on a 24-inch Full HD or 27-inch QHD screen. That is normal, not a fault.

Blocks cross the screen at a constant speed on dark, mid and light backgrounds. The measured refresh rate is shown in the corner.

• Ghosting: a long smeared trail behind a block. VA panels often smear more on the dark background; that is typical, but compare it with the other two lanes.
• Overshoot: a bright or dark outline that the block drags behind it, usually from the monitor's highest overdrive setting.
• Judder: jumps instead of smooth movement. Check the refresh rate and close heavy programs.

No test screen for this one: check the monitor itself.

• Scratches: switch the screen off and look at an angle with a window or lamp reflected in it. Scuffs on the coating show only this way.
• Buttons and menu: every button works, and the monitor's information menu shows the expected resolution and refresh rate.
• Ports: each input gives a picture with your cable.
• Stand and casing: adjustments hold, nothing wobbles or rattles, and there are no cracks.
• Noise: no buzzing or high-pitched whine at your normal brightness.
• Rear label: the model and manufacture date match what you were told.

Get-CimInstance -Namespace root\wmi -ClassName WmiMonitorID | ForEach-Object {
  [pscustomobject]@{
    Model = -join ($_.UserFriendlyName | Where-Object { $_ } | ForEach-Object { [char]$_ })
    Year  = $_.YearOfManufacture
    Week  = $_.WeekOfManufacture
  }
}