LED TVs come in two main varieties: back-lit and edge-lit. Generally, back-lit TVs produce the best picture but use more power and are more expensive.
While edge-lit televisions are cheaper but can produce a lower-quality image in some circumstances. But there’s more to it than that.
Read on for more details, starting with a brief explanation of how LED TVs work.
- LED TVs use LEDs to illuminate an LCD screen instead of traditional fluorescent lamps, allowing for thinner sizes, better brightness control, and less power use.
- Back-lit LED TVs place the LEDs behind the screen, either in local dimming zones for better contrast (full array) or directly behind without dimming (direct-lit).
- Edge-lit LED TVs place the LEDs around the perimeter, allowing for thinner sizes but can cause uneven lighting.
- Consider picture quality needs vs. budget/aesthetics to decide between back-lit or edge-lit LED TVs.
How Does an LED TV Work?
An LED TV is essentially an LCD TV – but with a different type of back-lighting.
The traditional method of back-lighting an LCD TV uses a cold cathode fluorescent lamp (CCFL).
This type of lamp has managed to produce high-quality televisions. But, there have always been disadvantages to this technology, such as poor contrast ratios and color reproduction.
The aim of using a different type of backlight is to fix some of these issues.
Therefore, televisions are now being built using the same LCD screens – but with light-emitting diodes (LEDs) to create the backlight.
Two different types of LEDs are used in making this type of television:
- White LEDs
- RGB LEDs (Red, Green, Blue)
RGB LEDs allow a more accurate color reproduction than TVs made with white LEDs.
So, now you understand the basics, you can group these TVs into two types depending on how they are made:
- Back-Lit LED Televisions
- Edge-Lit LED Televisions
So what is the difference between the two – and why should you care?
What Is a Backlit LED TV?
Back-lit LED televisions have the lights arranged behind the screen – similar to a traditional LCD with a fluorescent lamp.
There are several advantages to lighting the screen from behind – and the most important is more control over where the light occurs on the screen.
It also allows a more even spread of light across the picture. However, that isn’t always the case.
There are two main variations of this technique, back-lit with local dimming – and back-lit without any local dimming.
Back-lit LED with Local Dimming (Full-Array)
This type is usually called a full-array LED TV.
With this type of TV, the LED lights are grouped into blocks. Each block can be switched on or off independently of the other blocks.
You can get a completely black signal if a block of LEDs is switched off, which isn’t possible with fluorescent lamps.
This technique of switching off, or reducing, the backlight is called local dimming.
Different parts of the screen can have the blocks of lights switched on or off at any time, which gives the TV a much better contrast ratio than a traditional LCD TV.
The main problem with older LCD TVs has always been the poor contrast ratio and limited color spectrum.
Therefore, a back-lit LED TV with local dimming produces a better picture, which helps it to create an image comparable with other TV technologies like OLED.
You might want to check out the LED and OLED TV buying guide to understand the differences between OLED and LED TVs.
The downside of this technique is when you get an image that is a mixture of bright and dark areas.
If so, there will be some blocks of LEDs that cover a light bit and a dark bit.
In this instance, you will need the block switched on to reproduce the bright area, so the dark part will also be affected.
This can create a halo-like effect in dark areas of the picture – also called blooming.
The only way to completely get around this problem is to have one LED per pixel on the screen, but this would be far too expensive to manufacture.
However, this back-lighting technique is still widely regarded as providing the best images on LCD screens.
So, it is definitely worth considering this type of television if you want something close to an OLED TV’s picture quality.
A downside is that the power consumption of these TVs can be greater than standard LCD or edge-lit televisions – especially those models which use RGB LEDs.
Also, the light blocks behind the screen mean that a back-lit version won’t be as thin as the edge-lit models.
Back-lit LED without Local Dimming (Direct-lit)
These are often referred to as direct-lit televisions and are used for budget models – striking a compromise between edge-lit and full-array designs.
Direct-lit models are where the LED lights are arranged behind the TV but can’t dim specific screen parts.
The advantage over an edge-lit TV is that the lighting will usually be more uniform across the screen – eliminating the light-pooling of edge-lit screens.
Unfortunately, they don’t have the advantage of local dimming. So, the picture won’t have the improved contrast ratios that a dimming TV has.
Also, don’t assume that a back-lit screen will always have a more uniform light across the screen.
Some models aren’t that great in this respect, even though they should be.
What Are Edge-lit LED TVs?
Guess where the lights of an edge-lit LED TV are positioned?
Want a clue?
OK, it’s around the edge of the screen!
That’s right; the name is a bit of a giveaway, isn’t it? But this is important when looking at the performance of the TV.
The lights in edge-lit LED televisions are placed around the perimeter of the LCD screen – and the light they emit spreads across the back of the panel using a series of ‘light guides.’
You can summarise the main advantage of an edge-lit LED screen in one word.
Thin… skinny, slender, slim and lean.
OK, five words!
If you see a model that almost disappears when you look at it from the side, then you can be sure it is an edge-lit screen.
Another advantage of an edge-lit version is the power consumption is less than a standard LCD TV or a back-lit LED screen.
Aesthetically, these TVs look absolutely fantastic and would look great in any room in the house.
They will usually be cheaper than a back-lit model; however, this type of TV does have its issues.
The main downside is the picture quality.
The improvement over standard CCFL LCD TVs isn’t as significant as back-lit LED TVs.
An edge-lit TV will often have an inconsistency in the spread of the backlight across the entire screen.
In normal viewing conditions, you will usually not notice this.
But, if you are watching in a darkened room, you may see light pooling, whereas dark scenes may show brighter areas around the edge of the screen.
Edge-lit LED TVs with Local Dimming
In the early days of LED televisions, only back-lit TVs had local dimming technology.
It made more sense here, as individual blocks could isolate parts of the screen more easily.
As the technique became known for improving picture quality, it was introduced into edge-lit televisions too.
The problem is that local dimming doesn’t work well on edge-lit screens.
You don’t have light blocks behind the screen, so you can only alter the light from the sides, limiting the effect because there is less control across the screen.
So, even if you can find one, you shouldn’t buy an edge-lit LED TV on the strength of its local dimming.
There are advantages of edge-lit screens – but local dimming isn’t one of them.
You can see why it is crucial to understand the two different types of LED TVs. Each design has its advantages and disadvantages.
An edge-lit LED TV can be skinny, sexy and easy to install – but at the expense of picture quality. However, they are more economical to run than other types of television.
A back-lit LED screen has a better picture quality but at the expense of thickness and power consumption compared to an edge-lit model.
A back-lit LED TV with no local dimming provides a balance between the two – but just falls between two stools.
Obviously, the main result of these differences is the price you pay for a particular model.
About The Author
Paul started the Home Cinema Guide to help less-experienced users get the most out of today's audio-visual technology. He has been a sound, lighting and audio-visual engineer for around 20 years. At home, he has spent more time than is probably healthy installing, configuring, testing, de-rigging, fixing, tweaking, re-installing again (and sometimes using) various pieces of hi-fi and home cinema equipment. You can find out more here.