Function introduction:
1. High dynamic range imaging (High Dynamic Range Imaging, HDRI or HDR) is a set of technologies used to achieve a larger exposure dynamic range (that is, greater light and dark differences) than ordinary digital image technology.
2. The purpose of high dynamic range imaging is to correctly represent the brightness of a large range from direct sunlight to the darkest shadow in the real world.
Simple explanation: when use a photo device to take pictures, the following occurs in an environment where the light is not consistent: when click on the focus of the bright area, the details of the darker area are lost (dark), as shown in the figure:
3. When focus on a dark area, the bright area details are lost (overexposed), as shown:
4. HDR is a technique developed to solve this problem. It is a good way to preserve the details of areas with different light intensity, as shown in the image when HDR is turned on:
5. The principle is that the camera will take three photos in three different exposure degrees, and then synthesize them through a certain algorithm to get a HDR photo.
6. Due to the need for the recording and synthesis of three images, the requirements for mobile phone ISP (refer to No. 002406 in knowledge database for “what ISP chip is”) are high. For example, in Xiaomi 2, it will take a certain amount of time to turn on HDR to take pictures.
7. With the improvement of SoC performance, ISP performance also improves. For example, the time takes for a Xiaomi 3 to take a HDR photo and a normal photo is very close. Thus, it is called real-time HDR (after turning on the HDR effect). The effect of the screen display is the effect of the final imaging of the photo or video. There is no need to do operations at save time before optimizing).