QLED vs LED TV: What Actually Changes

Walk into a shop and QLED and LED are set out as two different technologies, with QLED as the newer and better one. They are not two technologies. Every QLED set on that wall is an LED television — the same backlight behind the same liquid-crystal panel — with one thin film added in front of the light. That film is the entire difference. It changes one thing a great deal and another thing not at all, and almost every disappointed buyer is somebody who expected it to change the second one. Once you know which is which, the choice stops being about the badge and becomes a question about the room you will watch in.

Both of them are LCDs, and everything follows from that

An LCD television makes no light of its own. Behind the picture sits a sheet of white LEDs that is always on while the set is on, and in front of that sits a layer of liquid crystal divided into pixels. Each pixel works as a shutter: twist the crystal one way and light passes, twist it the other way and most of it is blocked. The word LED in LED TV never described the picture at all. It described the lamp behind it, which replaced the fluorescent tubes older sets used. QLED is that same sandwich with one film inserted between the lamp and the crystal.

• The backlight is a lamp, always on, and never part of the image
• Each pixel is a shutter that blocks light rather than making it
• LED names the lamp, not the picture technology
• QLED adds one film to that stack and changes nothing else about it

What the quantum-dot film actually does

The film is a sheet of microscopic crystals, and the useful property of such a crystal is that its size decides exactly which colour of light it gives off when something shines on it. The backlight in a quantum-dot set is deliberately blue rather than white. That blue light hits the film, and the dots convert it into very narrow, very pure red and green. Mix those with the blue that passes through and you get a white made of three clean colours instead of a muddy one. The payoff shows up at high brightness: an ordinary LED panel tends to wash towards pale as it is driven harder, while a quantum-dot panel holds its colour. That is why these sets look so striking in a showroom, where the lights are fierce.

• Dot size decides colour, which is why the conversion is so precise
• The backlight is blue on purpose, not white
• Pure red and green mean colour that survives being driven bright
• The advantage is largest in a bright room, smallest in a dark one

What it does not do, and this is where buyers are let down

The film sits in front of the lamp, so the lamp is still behind every pixel on the screen. A shutter can close, but it cannot close perfectly, and the light leaking through a closed pixel is what you see as black. On a quantum-dot set that leaked light is just as present as on any other LCD. So a night scene is still dark grey rather than black, a letterbox bar still glows faintly, and stars on a black sky still sit in a haze. No amount of colour purity fixes this, because it is not a colour problem. It is a problem of where the light comes from.

• Black is leaked backlight, not an absence of light
• Quantum dots improve colour and leave black level untouched
• Letterbox bars and night scenes are where you will notice it
• Mini LED is the real answer here, and it is a separate feature

Mini LED is the upgrade people think QLED is

If black level is what bothers you, the specification to look for is the backlight, not the film. An ordinary set lights the whole screen from a handful of zones, sometimes only from the edges. A Mini LED set replaces those with hundreds or thousands of much smaller lamps, so it can drive one area bright and leave the area beside it almost off. That is where contrast comes from. The artefact worth looking for in a shop is haloing — a faint glow around something bright on a dark field — because how visible it is tells you roughly how many zones the set really has. Many sets are both Mini LED and quantum-dot; the two are independent and you pay for each.

• Zones, not colour, decide how black a dark scene looks
• Edge-lit sets have the fewest zones and the worst haloing
• Look for a bright object on a dark background to judge it
• Mini LED and QLED are separate features sold on the same sets

So when is the badge worth paying for

It comes down to the room. A living room with large windows and daytime viewing is exactly the case quantum dots were made for: you will be driving the panel hard, and that is where ordinary panels go pale. A room you darken for films is the opposite case, because at low brightness an ordinary panel holds its colour perfectly well and the thing you will notice instead is the grey where black should be. Size matters too. Below about 43 inches at a normal sofa distance the eye cannot resolve 4K, and panel quality differences shrink with it, so the money is usually better spent on the sound.

• Bright room, daytime viewing: the film earns its money
• Dark room, film nights: spend on backlight zones instead
• Below 43 inches the differences get hard to see at all
• Budget for a soundbar before upgrading the panel

What to try, in order

1. Decide first whether your room is bright or dark, because that settles most of it.
2. In the shop, find a scene with a bright object on a black field and look for a glow around it.
3. Read the panel type and the backlight separately — they are two different specifications.
4. Ignore the showroom picture mode; it is set for a shop floor and will look wrong at home.
5. Check the refresh rate only if you game; otherwise it changes very little.
6. Put aside part of the budget for sound, because a thin chassis has no room for speakers.

What to take from this

QLED is an LED television with a quantum-dot film in front of the lamp. That film buys colour that survives high brightness, which is a real advantage in a bright room and a small one in a dark one. It does not change black level, because the lamp is still behind every pixel. If dark scenes are what you care about, the specification to chase is the number of backlight zones, not the badge on the box.

Common questions

Is QLED better than LED?

QLED is a kind of LED television, so the comparison is not quite the one the shop sets up. It adds a quantum-dot film that keeps colour pure at high brightness, which helps most in a bright room. It does not improve black level at all, because the backlight still sits behind every pixel.

Is QLED the same as OLED?

No, and the names being one letter apart causes a lot of confusion. An OLED pixel makes its own light, so switching it off gives true black. A QLED is a backlit LCD with a colour film, so its black is leaked backlight. OLED wins on contrast; backlit sets usually go brighter.

Does QLED help if I watch mostly at night?

Less than you would hope. The film earns its keep when the panel is driven hard against bright room lighting. In a darkened room you are viewing at low brightness, where an ordinary panel holds colour well anyway, and the thing you will actually notice is grey where black should be.

What should I look at instead of the QLED badge?

The backlight. How many dimming zones a set has decides how black a dark scene looks, and Mini LED sets have far more of them than edge-lit ones. After that, the screen size against your viewing distance, and whether you will need a soundbar.