What is the blooming effect on TV?

Especially with LCD TVs that have LED backlighting, it is often noticeable that a white glow can be seen around very bright objects in front of a dark background. This is often referred to as blooming or the halo effect, because the artifact often looks like a halo. What is the blooming effect and where does it come from? We have summarized the most important information here.


What does Blooming mean? Definition and explanation

full moon blooming

A good example to show the blooming effect pictorially is a full moon in a night sky or subtitles in a very dark movie. If the edges are clear and distinct, then your TV’s backlighting works very well.

However, if you can see a bright glimmer around the moon or around the subtitle letters, then this is often a sign of uneven backlighting. These artifacts are called blooming or the halo effect because it often looks like a halo.

Clouding and Dirty Screen Effect

Other artifacts that can occur in connection with uneven backlighting are clouding and the dirty screen effect. The former is derived from the English word for cloudiness and describes brighter areas that can also occur on LCD TVs. Clouding is usually found at the edges of the TV.

The Dirty Screen Effect is especially visible during sports broadcasts. It means that the same color tone looks different in other parts of the screen. For example, the grass in a soccer game looks blotchy and uneven.

LED backlight: Two different types

To understand where such an artifact comes from, you have to take a closer look at the structure of an LCD panel. Here, besides the LED backlight, the Liquid Crystal layer is interesting first of all, which keeps the light out or lets it through.

Even more important, however, is the corresponding LED backlight that provides the appropriate light in LCD TVs. While the individual pixels themselves light up in OLED TVs, all LCD TVs rely on a backlight. Meanwhile, there are different technologies here and the price of a TV also plays a role since the better technologies are often saved for the expensive models.

Edge LED backlight

In this form of backlighting, the LEDs are usually located at the lower edge of the display and thus have to illuminate the entire screen. Dimming is possible here, but you can only dim the vertical stripes next to each other. TVs with edge LED backlighting are usually characterized by a comparatively low contrast and poor black levels.

Edge LED backlighting
Edge LED backlighting – Image © Sony.de

Full Array LED Backlight

This type of backlight, which is also often called Direct LED, is located directly behind the entire panel and thus fills the entire surface of the display. The backlight is divided into zones that can be dimmed individually. The more dimming zones a TV has, the better the result. This offers significantly more options for the illumination, which also simply looks more even overall.

What is Local Dimming?

Local dimming means that the individual zones can be dimmed locally and independently of each other. In the case of full array backlighting, this is referred to as full array local dimming, which is also often abbreviated as FALD. One advantage of full array local dimming compared to edge LED local dimming is that not only vertical stripes can be dimmed, but the respective dimming zones. The whole thing can be thought of as a grid of e.g. 5 x 6 rows, which ultimately results in 30 individual dimming zones. In practice there are significantly more zones and the larger the display is, the more dimming zones are usually present.

Due to the many dimming zones, a significantly higher contrast and a better black value can be achieved. Therefore, a well-functioning full array local dimming is always an enrichment for every LCD TV. Another advantage is also that a higher peak brightness can be achieved compared to an OLED TV. Especially with HDR content, highlights can stand out much better this way.

The dimming algorithm, i.e. the calculation behind the dimming of the individual zones, is also extremely important. This can be calculated better or worse by different manufacturers. A combination of the number of dimming zones and a well working algorithm ultimately leads to a better picture quality and less blooming.

Sony’s XR Backlight Master Drive

The manufacturer Sony announced at CES 2022 that it will bring back its own brand XR Backlight Master Drive technology. This is an algorithm that optimizes the backlight and was already found in the Sony ZD9 and the 8K TV ZG9.

The technology is said to be used on the Sony X95K and Z9K LCD flagships, both of which use mini LED backlighting. Here, XR Backlight Master Drive is supposed to cause the maximum brightness to be significantly increased and the blooming effect to be significantly reduced. This ultimately creates a better contrast ratio, which positively influences the overall picture quality of both TVs.

XR Backlight Master Drive: Powered by Cognitive Processor XR™, the XR Backlight Master Drive uses a Sony-developed local dimming algorithm to control thousands of tiny, ultra-dense Mini LEDs with absolute precision and independence, delivering extraordinary brightness, impressive dynamic range, deep blacks, and beautifully natural mid tones” © Sony-Pressemitteilung

Sony XR Backlight Master Drive
Sony relies on its proprietary XR Backlight Master Drive technology to minimize blooming. – Image© Sony

Alternatives and other technologies

Of course, there are other technologies that reduce blooming to a minimum, but it cannot be completely eliminated from LCD TVs. We have listed the different technologies here.

Mini LED backlight

Mini LED backlighting is not a really new technology because it is still based on LEDs. However, the LEDs here are much smaller than in a normal LED backlight, which is why many more LEDs fit into a panel.

Thus, much more dimming zones are possible, which ultimately also enables an even higher contrast as well as an even better black value.

Samsung introduced the Mini LED backlight to the market in 2021 and the flagship Neo QLED QN90A has 792 dimming zones in the 65-inch size and thus a very precise local dimming. Nevertheless, minimal blooming can occur here as well.

OLED TV

The self-luminous pixels of an OLED TV make a backlight obsolete. Therefore, they can also display a perfect black because the individual pixels then simply turn off completely. The contrast is also theoretically infinite, since each pixel can dim itself independently.

This also prevents blooming, since there are no individual dimming zones in an OLED. However, burn-in can occur here, even if the risk is only theoretical in the private sector. However, this is a reason for not having such a high peak brightness, since the Automatic Brightness Limiter turns on at some point to protect the pixels.

The LG C1 OLED is a prime example of an OLED TV with the perfect picture. Blooming can be found here in vain because every single pixel can shine itself.

FAQ – Frequently asked questions about Blooming

How does blooming occur?

A bright shimmer around light content on a dark background is called blooming. This image artifact occurs on LCD televisions because they rely on separate backlighting. Sometimes you will also find the term halo effect, as the defect can look like a halo. Depending on how well the backlight works, the blooming effect will be less.

Other image artifacts that are due to uneven backlighting are clouding and the dirty screen effect.

Is it possible to eliminate the blooming effect?

Blooming can never be completely avoided on an LCD TV, but it can be minimized. High-quality TVs that have a very good dimming algorithm and many dimming zones can minimize blooming better than inexpensive TVs that do not have a local dimming function.

Are there TVs without a blooming effect?

Since OLED TVs do not need a separate backlight, they do not have to deal with a blooming effect. Each pixel is lit independently and no local dimming function is needed for dimming.

Are there other technologies that minimize blooming?

Sony relies on the XR Backlight Master Drive technology for its expensive LCD TVs, which can additionally optimize the Mini LED backlight. Thus, the maximum brightness can be increased significantly, but blooming can still be further minimized.

This post is also available in: Deutsch


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