What is local dimming?

We demystify the specs around local dimming to help you choose the right LED TV for you…

When you’re choosing a new TV it can be hard to get your head around all the different specs.

One of these, local dimming, is actually really important to your TV’s picture quality. 4K UHD TVs (like HD TVs before them) use a type of screen called LED – but how can you tell the different options apart?

Wall mounted TV

What is local dimming?

Most new LED TVs aren’t actually real LEDs that use cold-cathode fluorescent lamps (CCFLs) to light up the screen. Instead the screens are made up of LCD pixels which are illuminated by tiny LED lights to create your picture.

By switching these lights on or off, particular areas of the screen can be made darker, while keeping the lighter zones bright. That’s what gives you the deep blacks and bright whites when you’re watching. 

There are two ways of doing this – edge-lighting or backlighting.


Edge-lit LED

Most TVs with local dimming are edge-lit. On these the LED lights sit around the edges of the screen instead of behind it.

This requires fewer LEDs than backlit models – which means the TVs can be thinner and more energy-efficient to run.

However, one downside to edge-lit LEDs being so slim is that it can worsen the screen uniformity – that is, how evenly the colours and contrast levels are distributed when you’re watching.


Backlit LED

Also known as full-array local dimming, these TVs have LED lights positioned behind the screen.

With a full-array backlit TV you can expect high picture quality and strong contrast. You’ll also get a more consistent picture as the screen uniformity is higher. 

A top-end full-array local dimming 4K TV – check out the Samsung SUHD UE65JS9500 Ultra HD 4K 65" Curved LED TV. 

However as it costs more to manufacture the TVs, they’re usually more expensive to buy.

Likewise, because the lights are all contained at the back of the LED panel, the TVs can be quite thick and heavy if you want to wall mount them.

While it’s not as commonly used right now, full-array backlighting is important for new technologies like HDR (high dynamic range). It works with HDR by making the picture even brighter – which gives it greater contrast.

To discover more information, see our article – What is HDR TV?


Edge-lit or backlit TV?

With both types of local dimming you’ll get brighter whites and deep blacks when you’re watching telly. It’s pricier, but a full-array backlit TV generally offers a more impressive picture.

However, TV makers are improving edge-lit displays – incorporating more local dimming zones so you get a similar effect to backlighting, while keeping the slim design.

If you’re looking for high picture quality at an affordable price and in a slim, lightweight design – then edge-lit TV is probably the right choice for you.

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