Before we answer, “What is an HDR TV?”, we must understand the different parts of the answer.
First, Let’s Talk Contrast
Even back when TVs weighed 50 lbs, the contrast was part of the settings. Most people didn’t take the time to understand what it meant. They just played with the settings until the screen showed them their favourite shows in a way that didn’t have the actors in Trump Orange.
The simple truth is that contrast cannot be measured.
It is the best estimation of the difference in luminance (light emitted) between the lightest (white) and the darkest (black) part of an image.
Most televisions and monitors have two separate “measurements” for contrast: static and dynamic.
Static contrast would be the contrast of the screen you are using to read these words, the amount of light produced by the white elements on this page, compared to the amount of light produced by the black elements. It is a static contrast because it isn’t moving.
Dynamic contrast would be the contrast of the screen if you switched over to YouTube or Netflix and started watching moving content. It is the average of the static contrasts for each frame, taking into account the on/off cycle of each pixel.
The reason for the two types is that screens generally cannot produce the same level of contrast when the image is constantly changing, so for a TV, the dynamic is the more important value, and usually, the only one advertised.
How Does Brightness Affect Contrast?
Long ago, brightness was a knob or a simple setting in a TV, that would just turn up the luminance of every pixel, even black. This had the unfortunate effect of making black into gray and dulling the hue of all colours if it was set incorrectly. Now, with our wonderful technology advances and our excellent LED-backlit LCD screens that promptly destroyed the march of the plasma TV through technological history, we have “Brightness” and “Backlight“.
Brightness will still cause colour distortion if set incorrectly. However, in a bright room, we now have the ability to make the screen brighter and more vibrant without changing the colours (except for black).
So, if you adjust Brightness, the difference between white and black, or the contrast, loses a massive amount of potential. If you use Backlight, the colour of colours stay the same and reach a higher luminance. However, adding light to black will still make it not quite the real black you see in real life.
Enter Stage Left, HDR
HDR, or High Dynamic Range, takes what was originally limited to the “Contrast” knob, and expands it significantly.
When a film is released in theatres, the director knows that the technology used is top-of-the-line and the film is made to top specifications. This allows them much greater control of the colour schemes and brightness of highlighted areas, such as explosions or stars.
Since most people don’t own a television that can produce the visuals that the projector in the theatre can, part of the process of going from big screen to small screen is stripping away the things that cannot be reproduced.
HDR expands the contrast and colour vividness of a TV to near theatre quality. It allows for much brighter, cleaner colours and much deeper blacks and brighter whites, without distorting the original intent of the director (like the “Vibrant” setting in non-HDR TVs does).
This allows TVs to display images much closer to what you would see in real life.
HDR, originally named HDR10, because it has a bit depth of 10 or higher compared to an 8-bit standard dynamic range, was released August 27th, 2015.
Since its inception, two newer versions of HDR have been released, HDR10+ (which adds dynamic metadata to the video signal, making it more efficient at changing the image and retaining high range and color), and Dolby Vision, which is a proprietary version of HDR that boasts a 12-bit color depth and 10,000 cd/m2 max brightness. Both are compatible with the new HDMI 2.1 standard.
For more information on how to put together an HDR setup, click here.