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HDR is a display technology, which is short for High-dynamic-range. This technology is used in flat-screen TVs, projectors and other places. It brings more realistic highlight and shadow detail. And, in terms of content, it has support for ultra-high-definition Blu-ray movies, video streaming media resources, and video games.
The display technology corresponding to HDR is EDR, which is a dynamic range. The greater the dynamic range, the richer the details of the highlights simultaneously recorded on the image. Therefore, we can know that HDR has a wider range of brightness on the image than SDR.
To understand HDR in depth, we also need to briefly understand other terms in the context of HDR display devices.
What are nits? The brightness of the output light of a display device is measured in nits—1nit=1cd/m². The higher the brightness presented in the display device, the higher the nits.
Then take the logarithm of 2 according to different brightness values, and then the values obtained are called stops on the image. See the picture below, from the darkest -5 to the brightest +5, it is called 10 stops dynamic range.
The dynamic range is the range of display brightness. If you want to improve the dynamic range and display it, you must be able to achieve the highest brightness.
The BT.709 (Rec.709) standard defines the display range of brightness and color. When the image display range exceeds BT.70, more brightness details cannot be displayed, and the picture becomes dead white in highlights and dead black in shadows.
The Rec.2020 color space standard is an upgraded version of Rec.709, and it is also the designated color space for ultra-high-definition devices. Compared with Rec.709, it can display more colors and a wider range of brightness.
The display technology corresponding to HDR is EDR, which is a dynamic range. The greater the dynamic range, the richer the details of the highlights simultaneously recorded on the image. Therefore, we can know that HDR has a wider range of brightness on the image than SDR.
To understand HDR in depth, we also need to briefly understand other terms in the context of HDR display devices.
1. Nits and Stops
What are nits? The brightness of the output light of a display device is measured in nits—1nit=1cd/m². The higher the brightness presented in the display device, the higher the nits.
Then take the logarithm of 2 according to different brightness values, and then the values obtained are called stops on the image. See the picture below, from the darkest -5 to the brightest +5, it is called 10 stops dynamic range.
2. Dynamic range
The dynamic range is the range of display brightness. If you want to improve the dynamic range and display it, you must be able to achieve the highest brightness.
3. Rec.709 and Rec.2020
The BT.709 (Rec.709) standard defines the display range of brightness and color. When the image display range exceeds BT.70, more brightness details cannot be displayed, and the picture becomes dead white in highlights and dead black in shadows.
The Rec.2020 color space standard is an upgraded version of Rec.709, and it is also the designated color space for ultra-high-definition devices. Compared with Rec.709, it can display more colors and a wider range of brightness.
