Dead Pixels, Dim Corners and the Dreaded 'Within Spec': Checking a New Screen Before the Returns Clock Runs Out

The box is open, the plastic is off, and the screen is sitting on the login page looking perfectly fine. Then you launch something with a dark background and there it is: one green dot, dead centre, like a grain of rice that won't wipe away. Or the new telly looks immaculate head-on but the bottom-left corner glows a milky grey whenever the credits roll.

You have a small window to do something about either of those, and the clock starts at delivery, not at the moment you finally notice.

Here's how to check a new screen properly, what manufacturers mean by 'within spec', and what you can realistically ask for in the UK once it turns out the answer is 'that's normal'.

First, learn the vocabulary

Dead pixel — a pixel that never lights up. Black on a white screen, invisible on a black one.

Stuck pixel — a pixel jammed permanently on, usually a single subpixel. Shows as a red, green or blue speck against a dark background.

Backlight bleed — light escaping around the edges of an LCD panel. Most obvious near the bezel in dark scenes.

IPS glow — a silvery haze in the corners of an IPS panel when viewed off-axis. It shifts as you move your head. Bleed doesn't.

Dirty screen effect — blotchy, faint unevenness that shows up on flat moving fields. Panning skies and football pitches are the giveaway.

Image retention — a ghost of a static logo or taskbar. Temporary on LCD, rather more permanent on OLED.

Two of those are faults. Two are physics. Knowing which you're looking at will save you a lot of aggrieved emailing.

What 'within spec' is really covering

Panel manufacturers grade their output against a standard called ISO 9241-307, which sorts pixel defects into classes and sets allowances per million pixels. A 4K panel has roughly 8.3 million pixels, so a class-based allowance can legitimately permit a few defects and still be considered compliant.

In plain English: plenty of warranties only cover a dead pixel once there are several of them, or once they cluster in the centre of the screen, or once a count buried in the small print is crossed. Budget lines are usually the most relaxed about it. Premium monitors and laptops sometimes advertise a 'zero bright dot' guarantee, which is exactly what it sounds like — and if you're the sort of person who notices one pixel from across a room, it's worth paying for.

None of that overrides your statutory rights, mind.

Where UK buyers actually stand

The Consumer Rights Act 2015 requires goods to be as described, of satisfactory quality and fit for purpose. A clearly visible defect in the middle of a premium panel is a decent argument. A single dim subpixel in the far corner of a £149 supermarket television is a much harder one.

The practical shape of it:

• 30 days from delivery or collection to reject faulty goods for a full refund.
• After 30 days, within six months, the retailer gets one go at repair or replacement before you can insist on a refund.
• First six months, faults are presumed to have been there at purchase — the retailer has to prove otherwise.
• Online orders also fall under the Consumer Contracts Regulations 2013: 14 days to change your mind from the day the goods arrive, then 14 days to get them back. Return postage may be on you unless the retailer says otherwise.

Retailer policies sit on top rather than instead. Several of the bigger names offer returns windows beyond the legal minimum, usually as goodwill and usually with conditions about packaging and condition. Check before you order, not after, and hang on to the box.

One thing to watch: a restocking charge or a flat refusal because a seal is broken isn't automatically lawful when the item is genuinely faulty, but arguing it is exhausting. Early photographic evidence is what tends to settle these things quietly.

The twenty-minute shakedown

Run this in the first day or two. You don't need special software — a full-screen colour page in a browser will do.

Set the screen to its native resolution, scaling off where you can, and brightness at whatever you'd genuinely use. Kill eco modes, dynamic contrast and anything with 'smart' in the name; they muddy the results badly.

1. Clean the panel with a dry microfibre cloth. Dust looks exactly like dead pixels and is far more common.
2. Black screen, lights dimmed but not pitch black. Look for edge glow and corner haze. Then stand and move side to side — if the haze follows your head, that's glow, not bleed.
3. White screen at your normal brightness. Look for dark specks, dust behind the glass and faint shadows.
4. Red, green, blue, then magenta, cyan and yellow. This is the only place stuck subpixels really show themselves. Vary the angle slightly as you go.
5. Mid-grey, about 50%. The uniformity test. Blotches, darker corners and faint vertical stripes all live here.
6. A smooth gradient. Chunky steps mean banding, which is usually the panel or the bit depth rather than your eyes.
7. For laptops and gaming monitors, load a motion test and watch for smearing or inverse ghosting on moving text.

If you have a phone with a macro lens, resist the urge to photograph single pixels and declare war. Camera sensors and exposure settings exaggerate this stuff enormously. Your eye, at normal viewing distance, is the judge.

Complain like you mean it, but calmly

Photograph the fault, note the brightness setting and what was on screen, and keep file names sensible. Then email rather than ring — you want a paper trail. Include the order number, the serial number, a short description and the photos.

Ask a specific question: 'Can you confirm whether this counts as a manufacturing defect, and what you'll do about it?' Vague complaints get vague replies.

If the answer comes back as 'within spec', ask them to send you the written specification they're applying. Some retailers will fold at that point rather than go through the paperwork. Others won't — and then it's a judgement call between a conversation with your card provider and simply learning to live with it.

The blunt version: a bright dot in the middle of a new premium monitor deserves a fight. One slightly warm subpixel in the corner of a cheap second screen probably doesn't. Either way, check in week one, not month eleven, when the goodwill has long since expired.