What is Local dimming technology?

Local dimming is a technology used in modern LED (Light-Emitting Diode) televisions and displays to enhance contrast and improve black levels.

LED TVs typically use an array of LED backlights behind the LCD (Liquid Crystal Display) panel to illuminate the screen. Local dimming allows for selective control of these LED backlights, adjusting their brightness or turning them off in specific zones of the screen. This targeted dimming can result in deeper blacks and increased contrast, making dark scenes appear more vibrant and detailed.

The basic principle behind local dimming is that when a particular area of the image is supposed to be dark or black, the LEDs behind that area are dimmed or turned off entirely, reducing the backlight bleeding or “halo effect” that can occur and enhancing the perceived contrast ratio. In contrast, brighter areas of the image can have the LEDs behind them turned up to maintain brightness and detail.

There are different types of local dimming techniques, including full-array local dimming (FALD) and edge-lit local dimming. FALD TVs have LED backlights arranged in a grid pattern behind the screen, allowing for more precise control over specific zones. Edge-lit local dimming, on the other hand, uses LEDs located along the edges of the screen, and the dimming zones are broader and less precise.

What is Local dimming technology
photo: Sony

Local dimming technology can greatly improve the viewing experience, especially in darker environments, by delivering deeper blacks, higher contrast ratios, and improved overall picture quality. However, the effectiveness of local dimming can vary depending on the quality and implementation of the technology in a particular TV model.

How to test test local dimming?

  • Find a suitable test video or image: Look for content specifically designed to test local dimming performance. There are various test patterns and videos available online that can help evaluate different aspects of local dimming, such as black level performance, blooming, and uniformity.
  • Dim the lights in the room: For better visibility of the display’s performance, dim the lights in the room or create a dark viewing environment. This will help you observe the effects of local dimming more effectively.
  • Adjust the TV settings: Enter the TV’s settings menu and make sure the local dimming feature is enabled. Some televisions may have different modes or settings related to local dimming, so ensure that it is activated according to your TV’s specific instructions.
  • Run the test content: Play the test video or display the test image on the screen. Look for scenes or patterns that specifically showcase dark areas, such as scenes in a dimly lit room or test patterns with black and white contrast.
  • Observe black levels and blooming: Pay attention to the black levels in dark scenes. The areas of the screen that should be black should appear deep and without any noticeable grayish tint or backlight bleed. Also, look for any blooming or halo effects around bright objects on a dark background. Blooming occurs when the dimming zones are not precise, and the backlight bleeding causes a glow around bright objects.
  • Evaluate uniformity: Assess the uniformity of the backlight across the screen. Look for any visible differences in brightness or color in different areas of the display. A good local dimming implementation should result in a uniform and consistent backlight across the entire screen.
  • Repeat for different settings: If your TV has different local dimming settings or modes, try experimenting with them and repeat the test to see how they affect the performance. Some TVs may have different levels of dimming or customization options for local dimming behavior.

Remember that the effectiveness of local dimming can vary between TV models and brands. It’s also worth noting that some test patterns or videos may be specifically designed for professional calibration purposes, so consider using reliable sources or consulting professional reviews for accurate testing guidelines.

Local dimming is designed to improve contrast on a television or display. By selectively dimming or turning off specific zones of LEDs behind the screen, local dimming enhances the difference between dark and bright areas of the image, resulting in a higher contrast ratio.

In scenes with dark content, local dimming allows the LEDs behind the dark areas to dim or turn off, which reduces the backlight intensity in those specific regions. This darkens the black levels, making them deeper and more accurate. As a result, the dark parts of the image appear darker, enhancing the overall contrast between dark and bright elements.

By controlling the backlighting in this manner, local dimming technology helps to mitigate the backlight bleeding or “halo effect” that can occur when bright areas of the screen bleed into adjacent dark areas, reducing the perceived contrast. The ability to selectively adjust the backlight intensity in different zones allows for more precise control over the contrast and can result in a more immersive and visually appealing viewing experience.

It’s important to note that while local dimming can significantly improve contrast, the effectiveness of the technology can vary depending on the quality and implementation in a particular television or display model. High-end TVs with full-array local dimming (FALD) tend to offer superior contrast performance compared to edge-lit local dimming configurations.

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