What is local dimming?
Behind the screen of an LCD TV, there are small lamps that produce a bright light. This makes the television display a clear picture. The disadvantage is that the dark parts of the screen are also illuminated, so that black images appear rather dark gray. If you do not want this, local dimming is a solution. This technology ensures that the lamps are dimmed or completely switched off at specific moments. In this way, a dark scene looks extra realistic.
Types of local dimming
Because local dimming is constantly evolving, you now have a choice of different variants. Cheap TVs usually have edge or back lit local dimming, while more expensive TVs have full array local dimming. Although all techniques improve black rendering, they also have disadvantages.
Full array is the best form of local dimming. Behind the screen are hundreds of small lights, or zones, that are dimmed individually. The dark parts become extra dark, while the bright parts remain bright. This powerful contrast is clearly visible during a scene of a starry sky. The stars shine brightly in the black sky. This technique costs more space than the other variants. The result is that full array TVs are often slightly thicker.
This technique is similar to full array local dimming, but consists of much fewer lamps. The screen of a back lit television has 4 to 12 zones that usually light up or dim at the same time. You can clearly see the difference with full array local dimming during the aforementioned scene of a starry sky. Back lit TVs recognize that most of the image is dark, after which they dim all lamps. As a result, the sky is deep black, but the stars shine less brightly.
Most TVs with local dimming have the edge lit variant. With this technique, the lamps are only placed at the edges of the television. This allows the screens to stay slim. The disadvantage is that the lamps have to shine extra brightly to illuminate the center of the screen. This sometimes causes distortions in the image. Think of light spots that arise at the bottom, top or side of the screen.
OLED TVs don't have background lighting, but 'self-emitting' pixels that light up individually or become completely dark. This way, black images are really black, without affecting the clear parts. A self-emitting screen ensures the strongest contrast between dark and light images.