Previously, we explained the LCD screen backlight layer. This article will explain the dimming technology used in the backlight layer and the closely related HDR technology.
1. What is HDR?
The abbreviation HDR refers to High Dynamic Range, a technology that allows display screens to display the different portions of your image (bright to dark) at different brightness levels. HDR achieves higher brightness dynamic range that results in greater immersion of the visual experience to images that are closer to real life scenes. With HDR, you see more details that you wouldn’t in shadows or highlights, with a result that’s overall crisper. Further, these technologies are commonly used together, notably Wide Colour Gamut (WCG). This combination more than doubles the range of colours that a display can display, providing more vibrant, truer to life colours. By working together, HDR and WCG give the display the power to do over a billion colour variations — to make the visuals really rich and really vivid, and it really comes to life when watching movies, playing video games and looking at high quality photos.
2. HDR Dimming Technology
The visual effects behind HDR technology are particularly due to dimming techniques that adjust brightness on the display based upon what you are showing. By adjusting these they make bright areas appear brighter and dark areas darker. This is what differentiates HDR visual from the regular ones — dynamic adjustment. The core of HDR technology lies in dimming technology, which can be categorized into two main types: Global Dimming, and Local Dimming. Both methods modify the backlight, but do so in different ways and how images are rendered on the screen is also affected. There are others inside local dimming, in fact 1D dimming and 1.5D dimming emerged within the realm of local dimming offering their own improvements to the viewing experience.
2.1 Global Dimming
Such a method of global dimming treats the display as a whole, something simpler than directly customising brightness for the entire display. It is usually used in display with an Edge-Lit LED (ELED) backlight structure. The ELED backlight compensates the brightness of the whole screen by increasing or decreasing according to the brightness of the image being displayed. In devices like such, like laptops, this method is used for lower power consumption, for slimmer, less heavy design, and managing heat generation. Nevertheless, the key caveat of global dimming is that the high contrast levels it is capable of producing are not sufficient. Since the brightness adjustment affects the entire screen uniformly, it cannot differentiate between bright and dark areas simultaneously, resulting in a contrast ratio that is generally capped at around 1000:1. Therefore, global dimming is energy-efficient; however it does not give the deep blacks and vivid highlights so importantly enjoyed by such advanced dimming systems.
2.2 Local Dimming
Custom dimming is a more complex variation of global dimming where local dimming is better in controlling how brightness can be controlled throughout multiple parts of the screen. While global dimming alters the entire display screen concurrently, local dimming suggests multiple segments of screen, all the segments of which might be made darkened or brightened independently. With this technology, you can have from deeper black shadows to brighter highlights just where you want them. Higher contrast ratios and more immersive visual experience are a result of this. Over time, as the technology has evolved, there have been emerging variations of local dimming, such as 1D local dimming,’1.5D local dimming,’2D (full array) local dimming which each favour specific ways to improve visual performance.
2.2.1 1D Local Dimming
1D local dimming is implemented by combining the use of a direct type LED backlight and side-lit LEDs in an additional row. The 1D local dimming technique places these side lit LEDs along the X axis to create a one dimensional array of dimming zones. Usually there are 8 to 16 dimming zones in this setup and light can be dimmed more specifically with the backlight, compared to global dimming. Keeping the contrast between the bright and dark areas of a scene high is easier when playing a video horizontally because it is wider than it is high. With 1D local dimming, displays can achieve a contrast ratio ranging from 6,000:It achieves a range of 1 to 100,000:1, providing a great improvement in image quality over any simple dimming method. It’s a popular pick for mid range displays that want a nice balance between price and performance.
2.2.2 1.5D Local Dimming
1.5D local dimming adds an extra row of side lit LEDs to the X axis i.e. placed at the top and bottom of a display that enhances 1D local dimming. This configuration is still oriented along the X axis but provides finer adjustment than standard one dimensional dimming. Second row of LEDs adds system to divide display into more zones, generally from 2×8 to 2×16 dimming areas. This avoids the problem of the screen covering too much (or too little) of the display’s height, which gives more control over how light is dispersed across the display in each zone. Added refinement in this control allows us to preserve details in complex images more cleanly; think of movies with high dynamic range scenes or games. It sits between the ease of 1D dimming and the complexity of 2D dimming.
2.2.3 Full Array Local Dimming (2D Local Dimming)
The most advanced type of local dimming is 2D local dimming, sometimes called Full Array Local Dimming (FALD). FALD employs a full array LED backlight distributed across the whole display for uniform illumination across the screen, as compared to the 1D and 1.5D dimming methodologies. The display is divided into hundreds or thousands of separately controllable dimming zones typically ranging from 384 to 1152 zones. However, each of these zones is independently controllable, making for an extreme level of control over light levels. As a result, FALD can achieve very high contrast ratios, ranging from 20,000:It’s also 1 to 500,000,1 to 500,000:1 especially when married with Mini LED backlighting. That means FALD is the preferred option for high end displays where image accuracy is critical — for example, a professional monitor or premium TV. But, as with any new technology, it does come with its own set of challenges, such as higher production costs, a heavier design, more complex circuitry, and the greater need for heat management, with the increase in the number of LEDs. FALD however, despite these challenges, offers top tier performance in visual performance and enhanced image quality for enthusiasts and professionals.
Summary
HDR technology has become a staple in modern display products, including smartphones, computer monitors, and televisions. Its ability to deliver vibrant, lifelike visuals makes it a key feature in many devices. As display technology evolves, high-end models now often incorporate Mini LED backlighting combined with Full Array Local Dimming (FALD) to further enhance HDR performance. These advanced setups bring unprecedented levels of brightness control and color precision, making them ideal for those who demand the best in visual quality. Additionally, more advanced iterations like XDR (Extreme Dynamic Range), popularized by products such as the Apple Pro Display XDR, have pushed the capabilities of HDR even further, offering an unparalleled viewing experience for users.
