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All about Backlighting and Dimming Technology Behind 4K TVs

by on November 8, 2016
 


When buying a LED TV, we certainly rarely notice about backlighting and dimming technology behind a LED TV. We prefer to notice more realism technology like 3D, Smart TV, Refresh rate, HDR or others where the impact is very clear even we don’t mind to pay dearly for those. The manufacturers are also rarely to list backlighting and dimming technology on the box or manual box. But do you know that backlighting and dimming technology has an important role on picture quality? The type of backlighting and dimming technology has a big impact on picture quality particularly on black level, black uniformity, and contrast ratio and indirectly also has an impact to the vibrancy of color. And there are many type of backlighting and dimming technology that used by LED TVs. Each type of backlighting technologies has their own distinct characteristic that effect on brightness and deep level that produced.

By know more about backlighting and dimming technology of a LED TV, at least we’ll get an overview how great contrast, brightness and black level delivered by a LED TV before you decide to buy it. Below, we will discuss completely all about most popular backlighting and dimming that usually used by a LED TV.

All about Dimming Technology

Unlike OLED TV where they have self lighting pixel, for allowing pixel color on LCD TV to function, it is required a light that pass through the LCD Display. So, LCD / LED TVs need a backlight as the light sources. But even so, this will cause a problem where a desirable area to black not look perfect black caused LCD Panel itself cannot bloc perfectly part of lights. To solve this problem, some LEDTV manufacturers develop dimming technology where it will dim a zone of LEDs behind the dark area of the picture. With other words, this technology will analyze the pictures and figure out the area that need to be dimmed then dims the light that pass through this spot.

Local dimming divides the screen on to some zones. The more zones of local dimming, the result is more precise and of course this will make the black level is deeper. This is caused the zone of LEDs behind the dark scenes will dimmed while the zones behind bright scenes still bright. OLED TVs with self lighting is the equivalent to LED TVs with zones of local dimming as many as the amount of pixels. But of course, for LED TVs, for this time it is impossible to apply pixel dimming on LED TVs because the physical shape of LED of backlights is bigger than pixel itself.

Local DImming

In other case, Sony has introduced frame dimming for some of their lineup. Actually it is the equivalent to Edge-Lit with local dimming technology but with fewer zones. Because the source of the light is not located behind the screen, dimming is made for LED that aligned with the black area. This would makes the level of precision is very low.

LED TV Backlighting Technology

There are three types of backlighting technologies that used for LED TVs for this time, Edge Lit, Direct Lit and Full Array Direct Lid. Usually, Direct Lit is used for cheap or entry level LED TVs, Edge Lit is used for middle class o even premium LED TVs while Full Array Direct LED is used for premium or top class LED TVs. But even so, this also depends on each of their manufacturers.

Backlighting Technology

Direct Lit

Direct lit is the type of backlighting technology that most common used by LED TVs with affordable price. As the lighting sources of LCD panel, there is a group of a lot of LEDs arrayed behind the LCD panel but each of LEDs cannot dim individually. This means, for dimming black area of the picture, it only depends on the ability of LCD panel in blocking light pass through. In other case, direct lit comes along with local diming technology. This means the arrayed LED behind LCD panel is divided into some zones where each zones is group of some LEDs. But usually, the number of zones and LEDs is limited so this means the level of precision is still low and cause hallo effect on bright point over a dark background.

Edge Lit

Edge Lit is usually used for middle or even top model of 4K LED TVs that available in the market. As the source of the illumination, is used LED TVs that located on the side of the LCD panel, whether they are located at the right and left, bottom and top, and also bottom or top. Edge Lit without local dimming means all of the LEDs located at the side of panel are turn off / on/ dimmed together. This usually is used for cheap or entry level ED TVs. The number of middle of top level LED TVs combines Edge Lit and local dimming. But because of the LEDs are not located behind the LCD panel, of course local dimming can only be applied the LEDs are aligned with the dark areas. Of course the precision of this technology is very low but better than no local dimming at all. The number of high end LED TVs which use edge lit with local dimming that perform a good job are Samsung Series 9 except for KS9800 or Samsung Series 8 KS8000 and KS9000. But even so, this does not only depend entirely on the great performance of their backlight and local dimming, but even depend more on how great their LCD Panel block the light pass through.

Edge Lit

Full Array Backlighting

Full Array Backlight or called FALD (Full Array Local Dimming) basically is Direct Lit Backlighting. This technology is usually used for top model or premium LED TVs that available in the market.  LEDs as the source of illumination are put right behind the LCD panel.  The differences, each of LEDs can turn on/off/dim individually or at least, the screen is divided into a lot of zones that contains a group of LEDs, even up to hundreds zones. On the same screen sizes, the more zones of local dimming this means the area of each zones is narrower.  And this allows affected area by LED Dimming is also narrower so this will improve the precision level. The result, black level is deeper while white area is brighter. In other hand, this also can minimize hallo effect. The premium LED TVs that available in the market like Samsung KS9800 is reported comes 120 zones of local dimming, Vizio Reference series comes with about 320 zones, or Sony X930D/X940D offers 98 zones where each of zones contains a group of LEDs

full-array-local-dimming

On its development, a dimming zone is not contains a group of LEDs but even single LED. This means hundreds or even thousands arrayed LEDs behind the LCD panels can turn off/on/dim individually and aim the narrower area of LCD panel in front of it so the precision of light control is much better. Sony’s flagship Z series is reported already uses this technology. And of course, we will see more top level TV LED TVs that come with this technology. At least, with single LED full Array Backlighting, it is approaching perfect performance offered by OLED TV that comes with pixel dimming, so this makes black level, peak brightness, and contrast ratio reached is much better than what reached by the best LED TV for this time.

Conclusion

Between all f these backlighting that we have discussed above, we can conclude that Full Array LED Backlighting with local Dimming (FALD) is the best technology for LED TV backlighting. It allows higher precision light control than the others. And the more dimming zones, the black level that reached is deeper. But unfortunately, due cost and complexity of FALD, the number big names of manufacturers only use this FALD for their flagship 4K TV models. 2016 4K TV models that already use FALD is Vizio Reference, P and M series, Samsung KS9800, Sony X930D/940D and Z series. Vizio M Series is sold much more affordable than other models, but it only has few dimming zones.

Some lower models like Samsung KS9500, KS9000, KS8500, KS8000, Sony X850D, and others have used edge lit with local diming as their backlighting technology. Performance that offered may not as good as what delivered by FALD, but it is still better than direct lit or edge lit without local dimming. Additionally, good performer like Samsung KS9500 and KS9800 depend more on the ability of their LCD panels in blocking light pass through than their local dimming itself.

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