[Display Glossary.zip] EP.21 : Halation
In displays, halation refers to a 'light bleed' phenomenon where the boundary of dark areas appears to blur with a white glow in high-contrast images, such as a crescent moon against the night sky. This is also known as the 'Halo effect.'
Halation primarily occurs in LCD products equipped with local dimming technology. Local dimming is a technology developed to enable LCDs to display deeper blacks. It works by dividing the LED backlight under the panel into zones, dimming or turning off the backlight in dark areas while increasing brightness in bright areas to control light partially. This helps mitigate the Phenomenon of partial backlight leakage in LCD panels.
However, local dimming technology cannot finely control light at the pixel level; it can only adjust by zones. In images where bright and dark colors are displayed together, 'light leakage' occurs from the active backlight, causing the boundaries of dark areas to blur with a white glow, resulting in the 'halation' phenomenon. Unlike local dimming LCDs, OLED displays, which use a self-emissive technology, can adjust brightness at the pixel level without a backlight, eliminating the halation phenomenon. As a result, they deliver sharper image quality without light bleed.
Display Glossary.zip