The halo effect (sometimes referred to as the FALD [Full-Array Local Dimming] blooming effect) takes place when light from small, glowing objects leaks into the neighboring dark environment.

The intensity of this effect depends on the number of dimming zones the display has and how challenging the image on the screen is to display. Display technologies, other than OLED, require a backlight to produce an image on the screen (which means that such technologies are unable to produce true blacks, unlike OLED’s). So as a consequence light will always leak or bleed through the panel of the display (the intensity of the bleed varies from panel to panel). This is why some users may also experience backlight bleed, IPS glow or VA glow (particular to IPS and VA panels respectively).

Checking for Halo or Blooming effect

In order to check whether your display suffers from the aforementioned effect or if you wish to measure the intensity of the effect, a star-field test can help you in your quest. The test checks for blooming or halo by playing a video of a star field. As the name suggests a star field has tons and tons of stars, each of which are separated by the sky (a black patch). The test is very effective when it comes to checking for halo, blooming, backlight bleed or black crush. If there is no blooming or halo, then you will see the stars as well as the black night sky between them. On the other hand, if there is a problem, then there will be halo’s encircling the stars.

Fixing the effect

Sadly, there isn’t much that can be done when it comes to fixing or, in the first place, avoiding such effects. As sated above, all these effects vary from panel to panel, meaning that some might have them and some might not. There is, unfortunately, nothing that can be done about it and you can’t claim warranty on this either. However, all is not lost, if your device offers local dimming settings, then you can use them to control the, above mentioned, effects and achieve the best possible experience. By lower the backlights in certain areas the blooming or halo will become less visible. Although, this will cost you, a drop in your displays contrast ratio.

If you try to fix the contrast ratio by changing the local dimming settings then the blooming will become more noticeable. So it’s safe to say, you can’t have one without the other.

Conclusion

Until the day comes when OLED display prices can compete with the prices of LED display, FALD will be the key element in helping LCD/LED displays provide brightness and contrast ratio that can match OLED’s. What this means is that blooming can’t be avoided, reduced but not avoided and changing local dimming settings with only let you achieve two states. Great contrast ratio with blooming or less noticeable blooming with bad contrast ratio.