1. What is “good picture quality” of HdTV
When you ask anyone what a good HdTV is, almost everyone will answer “good picture quality”. But when it comes to what is called “good picture quality”, many people can’t answer it. In our opinion, whether the picture quality of HdTV is good or not can be simply divided into three dimensions: brightness, color and clarity.
(1) HdTV Brightness
On HdTV, brightness doesn’t mean how bright the screen is at its brightest. It’s going to be bright when it’s time to light up and dark when it’s time to dark. For example, when we look at a scene in the night sky, there is a bright moon in the sky. When a good TV shows this scene, it should be that the moon is very bright and the night sky is dark.
But in fact, most of our television is like this:
The biggest reason for this effect is the screen backlight. What many people may not know is that the LCD itself in LCD TV does not emit light. It needs a backlight to illuminate the whole screen, just like an old-fashioned advertising light box on the street. Only when the light is turned on can the contents of the light box be seen clearly.
Therefore, in order to solve the problem of the influence of screen backlight on the image quality, manufacturers introduce the partition backlight technology. Through a special algorithm to control the entire backlight module, so that the bright place is bright and the dark place is dark. Therefore, whether there is partition backlight technology and the number of partition backlight also become an important basis for dividing HdTV grades.
Low and medium end TVs generally adopt the low-cost “strip-shaped zoning light control”, and the above moon scene makes us feel like this on HdTV:
Although this method saves the cost, there is little improvement in the appearance. The middle and high-end TVs will adopt the chessboard division light control technology. For the same moon scene, our impression is like this:
For example, the high-end LCD TVs of Sony and Samsung will divide the backlight module of the TV into hundreds of zones, and provide the moon with thousands of nits of peak brightness to restore the purity of the night sky. For example, Apple’s previous Pro display XDR monitor further uses smaller Mini LED as the screen light source. On the 32 inch monitor, it achieves exaggerated 576 partition, and the price also reaches an amazing 47999 yuan.
In addition to LCD TVs, OLED TVs have also emerged in recent two years. Compared with traditional LCD TV, the biggest advantage of OLED TV lies in the self luminous characteristics of OLED screen. In short, each pixel of OLED TV can be used as a backlight partition to control the brightness of the picture. This is also why Huawei TV and Xiaomi TV, which have just risen in the past two years, have chosen OLED screens in high-end product lines.
The second factor that affects the brightness of the screen is contrast. Contrast refers to the difference range between the brightest and darkest pictures on TV. The larger the difference range, the greater the contrast. The self luminous property of OLED screen gives the TV infinite contrast, and high-end LCD TV also achieves extremely high contrast through advanced partition backlight, but the screen alone is not enough.
Xiaomi 65 inch OLED TV achieves a contrast ratio of 1 million to 1
The source of the program shooting equipment we see everyday is very complex. Coupled with the chaotic processing of the compression software, even if the OLED screen is used, the picture is as foggy as the ordinary LCD TV. Therefore, in addition to the top-level screen, high-end TV will also add advanced algorithms and special chips to re distinguish the light and dark contrast of the screen, so as to make the “Moon” brighter and the night sky darker. This algorithm is called “dynamic contrast enhancement” in Sony and local DCI in Huawei.