1: What is the effect of true HDR?
Copy and translate people’s articles is not my habit, and most people read it actually still can not have the actual experience, thought for a long time, looking for a simple method, everyone can practice.
1.1 Take your phone, take a picture of the lights in your house, and then play back this photo, you carefully compare the lights in the phone display and the lights in reality, they bring your eyes in the brightness of the feeling of difference, is one of the most obvious differences between HDR and SDR, but also HDR is an important step toward restoring the real world.
I measured the surface brightness of the lampshade through the luminance meter, about 3500nit (cd/m2), which is a 7w LED bulb, the phone is not a good model, when the brightness is turned up to the maximum, the light in the photo shows a brightness of about 520nit, in fact, this has exceeded the brightness level of most TV sets.
The human eye can feel the brightness range of about 0.001-1,000,000nit (no need to count a million), can adapt to the brightness of 3000nit, is in line with the brightness of the sky during the day and the brightness of darker objects in the sun (such as land, plants), but also necessary for human survival on Earth. It can be understood that, seeing the brightness of 3000nit, the pupil of the eye will not be very obvious shrinkage.
1.2 After talking about white, say black, I saw this photo in JPG format, only 8bit 256 gray scale SDR image, in order to make people look real, there have been dark details and highlight details were discarded.
In reality, I shot in RAW format, which has saved all the signals that the sensor can record. By turning up the exposure (+2.65ev), we can see the dark part of the first photo with more image details (the blue circle part), but at the cost of losing the highlight details, which is the limitation of SDR images and videos.
Similarly, by reducing the exposure (-2.65ev), we get this photo with more highlight detail, and you can see that the circular bright spot of the original light in the middle is another ceiling light on the ceiling. Of course the price is more detail loss in the dark areas.
1.3 SDR pictures and videos can not show the real world of light and shadow
Speaking of which, many people think of the so-called HDR photos, HDR photos in JPG format look all weird and require some adjustment steps to produce. I will directly find one to demonstrate this kind of photos in SDR format files forcibly adding highlights and dark details, although they look different, they are seriously distorted and very different from what we actually see with human eyes.
Pseudo-HDR pictures with multiple exposure synthesis
HDR video’s ability to reproduce details in dark areas
The above explains the significance of HDR video through a photo: to record and present a more realistic picture of light and shadow, which requires not only the support of the content source, but also the support of the display device. HDR video and images are a visual revolution that enables us to record and show highlights and dark details that could not be captured or displayed in the past.
Two: The three necessary conditions for a true HDR TV
High brightness (range), high color gamut, and 10bit/12bit grayscale restoration are the three necessary elements of a true HDR TV.
Of course, it should also support HDR10, HLG, HDR10+, Dolby Vision (DV) and other HDR encoding formats, otherwise it would be depressing to take different HDR sources but not be able to play them correctly.
10bit allows HDR sources to present richer bright and dark image details, wide color gamut can present closer to the real-world ability to restore highly saturated colors, and high brightness is a necessary prerequisite to present these brightness and color differences.
Comprehensive metadata from hundreds of HDR videos from different sources shows that the demand for peak brightness is at least 1000nit or more, and the need for 4000nit is not small, so the basic requirement for TV selection is that the peak brightness should be up to standard. When the display device can not reach the brightness level contained in the source, it will use tone mapping.
Where does such high brightness appear?
High brightness is not a brightening of the picture as a whole, but rather a brightening of the highlight areas of the image to show a more natural brightness variation. The high luminance range and high color gamut range define the boundaries of HDR images, while the ability to restore grayscale above 10bit is necessary to correctly present the PQ curve.