HDR mode in the smartphone’s camera allows you to capture better photos,brings the colors out more vividly and finds the details in the shadows. However, HDR is not only for capturing images but also for displaying images.
HDR stands for higher dynamic range,the idea is that it gives you a display that gives you more vibrant colours,greater brightness,greater contrast. Hence a better picture in your smartphone.
There are different competing standards, different competing ideas about what exactly HDR means and whether a display qualifies to be listed as a HDR display.
There are three important ingredients for a HDR display.
The first is Brightness,the display has to offer a high level of brightness,the reason for that is to have a good level of Contrast. Contrast is the difference between the brightest pixel on the screen and the darkest pixel on the screen. The brighter the pixels you can get on the screen and the darkest the pixels you can get on the screen,the greater the contrast.
The brightness and the contrast together will give you the sharpness you want on your display.
Once you have a bright display with good contrast the next thing you need is vivid colours. Colours in our smartphone displays are made using a combination of Red,Green and Blue (RGB). And each of those colours (Red,Blue,Green) are given 8bits of information; 256 types of Red,256 types of Green,256 types of Blue and when you combine them you get 16million colours (16M colours).
The human eye can see more than 16M colours hence that’s why HDR is recommending use of a new colour space called Rec 2020. In Rec 2020 it defines an area that takes 76% of the visible spectrum,to get that level of colour we need to move more than 8bit coding of colour to 10bit or 12bit coding of colour.
When you get to 10bit of colour,you now get 1000 types of Red,Blue and Green. When combined together you get more than a billion types of colour. To get most from a HDR display you need to watch HDR content. If you’re watching a movie or a series encoded with 8bit of colour you can’t invent those 2 extra bits of colour to get a 10bit display. To have full HDR display you need to watch a media that has been recorded and encorded in 10bit or 12bit colour.
It’s important to note that not all video formats support 10/12 bit colour for example mpeg 2. But some of new codecs like the H.265 and some profiles for H.264 support 10bit colour media.