The more you get into watching movies, the more you notice the effects that black levels can have on the immersiveness of a movie. TVs are investing in technology to improve the black levels of their displays, OLED displays innately have amazing black levels, but QLED TVs rely on technology such as local dimming to improve their black levels.
With QLED TVs, they cannot switch off individual pixels for dark scenes, they always remain lit and depending on the image on screen, the blacks can appear as washed out. This is why local dimming exists, to deepen the blacks and increase the contrast ratio to make movies/TV shows seem more realistic.
In this post, we’re going to go over what local dimming exactly is and how it works, if local dimming makes a good difference in movies, and the different types of local dimming. If you’re unaware of the types of local dimming, there is Full-Array, Direct-Lit, and Edge-Lit.
What Is Local Dimming?
Local dimming is a technique where the TV or display makes dark areas on the screen appear extra dark, this is done by dimming or completely turning off specific backlights. This is to avoid the blacks looking grey which can ruin the immersive experience, you will often find this kind of technology on QLED displays.
Local dimming essentially increases the contrast ratio of your screen, and a TV with higher contrast ratios can produce more meaningful images and display more detail. A TV can have a native contrast ratio of 5000:1, but local dimming can help increase this, OLED TVs have infinite contrast ratios (inf:1) because they can individually light and turn off each pixel.
A QLED TV will have a set number of dimming zones on the screen, these zones will darken when the time arises, usually in a dark scene. For example, the QLED Q90T has 120 local dimming zones, and these zones will be dimmed individually corresponding to the dark areas on the screen.
Local dimming can have a massive effect when watching movies, there’s no problem watching movies on a screen with no local dimming/self illuminating LEDs. But if you’re serious about building a home theater setup with maximum immersiveness, then a decent QLED, or an OLED TV can make a massive difference.
Also Read: TV Contrast
What Are The Types Of Local Dimming?
There are 2 types of local dimming, and each have varying effects, the types of local dimming are Full Array, and Edge Lit. The best Local Dimming method is full array, but the others still help make images on screen look better, but with the best technology comes higher prices, but we’re going to explore whether it’s worth it or not.
Full Array Local Dimming has an array of dimming zones which will dim or turn off pixels to the corresponding dark spot on the screen. FALD is for those who want deep darks on their OLED or LCD screen, but this technology is more expensive compared to Edge and Direct lit screens.
Edge Lit Local Dimming has dimming zones on opposing sides on the screen, and just like the name, it will dim two different sides of the screen usually causing vertical lines where it isn’t dimmed. Edge Lit local dimming usually doesn’t increase the contrast ratio of the screen so it’s usually avoided.
Direct Lit screens work similarly to full array as they both have dimming zones placed all over the screen, usually fewer. Direct lit screens do not use local dimming, so they won’t be able to produce deep blacks like FALD screens. Direct Lit screens will often produce greys instead of blacks, for this reason, Full array local dimming screens are the best when it comes to local dimming.
The Downsides Of Local Dimming
No Local Dimming technology is perfect at producing deep blacks because of how QLED and LCD displays work. What Local dimming is really trying to do is replicate how OLED TVs work with their deep blacks, so if you want the perfect TV for deep blacks, OLED is the way to go as each pixel is essentially their own dimming zone.
A massive problem with TVs with local dimming is the light blooming or halo around bright objects, and it is caused because the bright objects will often bleed light onto the dark areas of the screen. Blooming objects are often caused with full array televisions, OLED TVs are self emissive so they will never bloom.
Another downside is Black Crush, and this is caused when you have a dark area on the screen and a dark object and if the object is dark enough all details are essentially crushed together resulting in no detail in the object. TVs often struggle to show details in dark areas or the black object and crushes them together, essentially there is no differentiating between the object and the background,
To conclude the post local dimming is only worth it if you’re going for the full array option, local dimming techniques such as edge lit isn’t worth it and have minimal effects on the contrast ratio. You should probably avoid all edge lit displays and go for FALD displays even if they cost a little more, it’s worth it for the extra immersiveness.
Essentially, Local dimming aims to replicate the self illuminating effects that OLED TVs have which is deep blacks, but local dimming will never be as good as OLED TVs. Full array TVs aren’t perfect and they can suffer from blooming which causes bright objects to bleed light onto the darker areas of the screen. Also, black crush is an issue which causes blacks to lose their detail in dark scenes, dark hair and usually objects such as guns suffer from this a lot.
For HDR content, local dimming can make a massive difference compared to the native contrast ratio, so if you’re looking to build a home theater, this can make a massive difference. Washed out blacks and greys will produce a poor HDR experience, so it’s recommended to go OLED or Full array.