What does HDR of Apple camera mean?

HDR is the abbreviation of English High-Dynamic Range, which is translated into Chinese as high dynamic lighting rendering. HDR can make 3D images more realistic, just like people's eyes are in a game scene. With the help of HDR, we can use color values beyond the normal range, so we can render more realistic 3D scenes.

When taking pictures in an indoor environment with a big difference between light and dark, the effect of turning on the camera HDR function is obviously softer and clearer. In other words, a camera with HDR function works better when taking pictures in an environment with a big difference between light and dark. At present, many cameras have this function, but only some mainstream mobile phone cameras support this function. Friends who like to take pictures can pay more attention to whether the built-in camera of the mobile phone supports HDR function when buying a mobile phone. Introduction of camera or camera function: HDR refers to a picture with high dynamic range. Due to the limited dynamic range of the photosensitive element of digital camera, if the light ratio at the scene is particularly strong, if the exposure is determined according to the strong light, then the weak light will be dead black and no level can be seen. If the exposure is determined according to the weak light, then the strong light will die white.

HDR is the abbreviation of High-Dynamic Range (HDR) image, which is invented to solve this problem. Simply put, HDRI is an image with a very wide brightness range, which has more brightness data storage than other formats, and its way of recording brightness is also different from that of traditional pictures. Instead of compressing the brightness information into the color space of 8bit or 16bit in a nonlinear way, we record the brightness information in a directly corresponding way, which can be said to record the illumination information in the picture environment, so we can use this image to "light up" the scene. Many HDRI files are provided in the form of panorama, and we can also use it as the environmental background to produce reflection and refraction. It should be emphasized here that HDRI is fundamentally different from panorama. Panorama refers to an ordinary image containing a 360-degree scene, which can be in JPG format, BMP format, TGA format, etc. It belongs to a low dynamic range radiant brightness image, and has no illumination information.

HdrI file is a file with an extension of HDR or tif format, which has enough ability to save lighting information, but it is not necessarily a panorama. Dynamic range refers to the relative ratio between the brightest and darkest parts of the scene. An HDR picture records the brightness value of the actual scene far exceeding 256 levels, and the excess part cannot be displayed on the screen. You can imagine: in photoshop, open a picture taken indoors and out of the window. The part outside the window is overexposed in the strong sunlight, showing a piece of white without too many details. Nothing you can do can stop it. Dimming will only turn white into gray without showing more details. But if you record the same scene with hdr, if you reduce the exposure, the original pure white part will show more details. When it comes to game screens, what exactly is HDR? HDR itself is the abbreviation of high dynamic range, which was originally a CG concept.

When a computer represents an image, it uses 8-8bit(256) level or 16bit(65536) level to distinguish the brightness of the image, but these millions or tens of thousands can't reproduce the real and natural illumination. HDR file is a special graphics file format. Each pixel of HDR file contains not only ordinary RGB information, but also the actual brightness information of that point. Ordinary graphics files only have a gray range of 0-255 per pixel, which is actually not enough. Imagine the difference between the luminous intensity of the sun and the gray range or brightness range of a pure black object, far exceeding 256 levels. Therefore, in an ordinary daytime landscape picture, it seems that both the white clouds and the sun may present the same gray level/brightness, all pure white, but in fact, the actual brightness between the white clouds and the sun cannot be the same, and the brightness difference between them is huge. Therefore, the ordinary graphic file format is very inaccurate, far from recording the actual situation in the real world. So, now we will introduce high dynamic range image (HDRI). The full name of HDR is high dynamic range. This is a simple term. HDR pictures use multiple pictures with different exposures, and then use software to synthesize a picture. Its advantage is that you can finally get a photo with details of shadows and highlights. In normal photography, maybe you can only choose one of the two.

application area

The Best Partner of HDR: OLED TV

The image quality improvement brought by HDR technology is intuitive and tangible, and even ordinary viewers can distinguish it with the naked eye. Therefore, many manufacturers installed HDR technology on TV products this year. But even so, not all TV products can become "good rivals" of HDR technology. After all, the application of HDR technology is not a single link, but related to the entire ecosystem of screen display.

Presenting perfect HDR requires two conditions, the first is high contrast, and the second is excellent color expression. Different from the traditional LCD technology, OLED TV abandons the backlight and realizes the organic self-illumination of each pixel, which means that each pixel can be turned on or off independently, which has the advantages of infinite contrast, wide color gamut and wide viewing angle, so HDR can be used in OLED TV.

First of all, the most important thing for HDR is contrast. The lowest brightness that LCD TV can display is 0. 1 nits, the brightest is between 500 and 1000 nits, and the contrast is only 5000 to 1. If the brightness is doubled to 10000 nits, it can only reach 10000 to 1. The lowest brightness that LG OLED can display is 0.0005 nits (the lowest brightness that can be detected by brightness measuring instrument at present), and the highest brightness is 500 nits, which is about 20 levels. The contrast ratio is 1 10,000 to 1, and the lowest brightness (0.0005nit) is almost zero, which is equivalent to having an almost infinite contrast ratio. ?