Local Dimming Explained

Local Dimming Overview

There is a little bit of magic between two things working here that make local dimming not only a great feature for a TV, but a preferred one. The LCD crystals, and the control we have over them.

Simply put, the LCD structure of the TV has newer and better technology than that of prior years allowing for the LED lights to perform better and also allow the TV more control over the LED light at any given time. In turn this allows us to program the TV to lessen the LED under the part of an image or scenes that is displaying a darker (black) color. This allows for a better viewing experience not only in a darker room, but better experience overall.

With that said, I’ve listed some types LCD/LED backlights below.

 local-dimming-trt
What it is: The lights behind the LCD layer.
Why it matters: Improving the contrast ratio by controlling the lights behind the LCD layer.
When it matters: Dark images and scenes viewed in a dark room.

Types of LCD/LED Backlights

There are not many types of LCD and LED back-lights, but even with a small amount, they produce a large variety of picture values.

Edge-lit LEDs In which the LEDs are formed around the rim of the screen, using a special diffusion panel to spread the light evenly behind the screen making it the most common.  
Full-Array LED Behind the screen, whose brightness is not controlled individually  
Dynamic Local Dimming LEDs are controlled individually (or in clusters) to control the level of light/color intensity in a given part of the screen.

These are the most common types and to be honest the only types you’re likely to see implemented in any TV nowadays.

Local Dimming Techniques

These are the most common and honestly the only implemented ways to handle local dimming.

Full-array LEDs Many brands use LED backlighting technology, which offer the advantages over CCFL LCDs of reduced energy consumption, better contrast and brightness, greater color range, more rapid response to changes in scene and more accurate image rendering.  
Dynamic Local Dimming LEDs This method of backlighting allows local dimming of specific areas of darkness on the screen. This type of display comes in white or the more expensive RGB LED configuration. This can show truer blacks, whites, proper color saturation. Some of the best TVs can control individual LEDs such as the LB B6.  

Silhouette Test 

A little bit of a information overload, but if you’re still with me, there is a simple way to test how well the local dimming features are working or at all. Some people that are sensitive to judder or flickering may want to be careful during these steps. What you will need to do is wave your hand slowly in front of the screen while you watch your hand past back and forth. As you watch your hand past back and forth is the silhouette of your hand smooth and does it have sharp lines? If so, the backlight is flicker at a fairly lower frequency. On the other hand is the silhouette blurry, the display has a continuous backlight that is illuminated non-stop or perhaps the frequency is too high for your eyes to perceive. This is preferred for the best local dimming options that your hand be blurry.

There are often times settings to help reduce flicker if that does bother you, but at the same time those same options are often limited. I would not count on them to be the best.

Conclusion

PROS:
  • Offer a wider color gamut (when RGB-LED backlighting is used).
  • Produce images with greater dynamic contrast.
  • Allow a wider dimming range.
  • Can be extremely slim.
  • Are significantly lighter, often as much as half the total chassis and system weight of a comparable CCFL.
  • Run significantly cooler.
  • Have (typically) 20–30% lower power consumption.
  • Longer Life span.
  • Are more reliable.

CONS:
  • Can be too strong and cause blooming.

It’s clear to see why local dimming options have become a staple with modern day TVs. Whether you’re looking at cheap TVs for sale, or the best TVs out there, they should come with some sort set of features. It’s almost a better question to ask why not have these options.

Overall though, they offer sometimes a drastic increase in the contrast ratio of a TV. This is great for viewing the TV at night or in a poorly lit room as well. To add, the local dimming features are efficient and help the TV conserve energy while all at the same time performing very well.

LET ME KNOW WHAT YOU THINK IN THE COMMENTS BELOW!

2 Comments
  1. I recently purchased Sony 85”850 D which is edge lit at excellent close out price getting ready for new model with agreement from retailer to allow me to upgrade to to Sony 85” 900F for the difference in price. The new one just came on the market which is full- array with local dining and a better processor. The difference in price is $1,800. So far I have been pleased with the picture on the 850 D.If money was not a big factor, In your professional opinion would the new model be worth the difference in price? I HAVE TO GIVE THE RETAILER MY DECISSION BY TUESDAY MAY 15TH. N

    • I believe the Sony X900F is a serious upgrade 100%.
      Without worrying about money that should be the choice of smart TV for most general uses in my honest opinion. There is no risk of permanent burn-in like with an OLED TV. Not to mention it comes with all the bells and whistles you need to watch any kind of content without worry.

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