What’s so special about those HDR TVs?

Remember the first time you saw an HDTV? Chances are it wasn’t the level of detail you remember, it was something… else. It was like you were looking out a clean window for the very first time. Colors were brighter, shadows were darker, and everything was much more immediate. It just had a very electric quality that you couldn’t quite define.

It’s taken about a decade for TV makers to realize it, but that “pop” has much more to do with why people buy TVs than almost anything else. Getting people to put out another $1,500 for a TV after doing it fewer than ten years ago has proven hard, and it turns out it’s the lack of “pop” that’s keeping people’s credit cards in their wallets. In order to understand how to loosen those purse strings, and understand why they’re so tight now, we need to take a few steps back.

The word you need to understand is gamut. It’s a technical term that means “the difference between the brightest and darkest things that can be displayed by a device. It’s not easy to understand gamut, but I’ll try to lay it out.

Everything that is capable of showing images has a gamut. That’s printed pieces, TVs, everything. Think about an image in a newspaper (yeah, you first have to try to remember what a newspaper is) and the paper is grey and the black ink is really dark gray. Nothing can be lighter than the paper or darker than the ink. So pictures always look muddy because of that. We call that a “small” gamut.

As the gamut gets “larger” then the whites get whiter, the blacks get darker, and everything in the middle gets brighter. If you’re looking at a painting in a museum, it may strike you as having incredibly intense colors. The blues may totally pop, the greens may strike your eye… and that’s because the painting has a “large” (sometimes we say “wide”) gamut. It’s a combination of the paints themselves and the special lighting that’s being used.

Now let’s take this to the world of TVs. Older tube TVs had a fairly small (or “narrow”) gamut. The black was never really terribly black and the white wasn’t super-bright. Compare that to the latest OLED TVs, the white is 2-3x brighter and the black is as dark as the lighting in your room will allow. That is what makes the image really pop. It’s not the size or the detail as much as the difference between the white and black, which naturally pushes the saturation of the bright colors while maintaining the subtlety of the dull ones.

If you take a look at the image at the top of this article, you’ll see a little bit of what I mean. The outer area is a regular image, while the inner area has a wider gamut. Even though the grey areas look the same everywhere, the colored areas really pop. When an image takes advantage of the full gamut of today’s modern display devices, we call that “high dynamic range,” or “HDR.”

The importance of HDR is something that TV makers are just really coming to understand. They’re making new display panels that can show a very wide gamut, and they’re also starting to include software that helps regular images take advantage of that gamut. The next step is to make content that’s actually designed to use that full gamut, and make sure it’s preserved from beginning to end.

For a decade now, content providers have been using “gamut compression” to create HD images that take up less space on a disc or as part of a broadcast. They have intentionally been making images flatter looking because they were more worried about detail than “pop.” As it turns out, this may have been a mistake, although it was probably necessary in the past to keep HD systems working. That line of thinking has to change now that devices can actually show that full, wide gamut and now that we understand how important it is.

You’ll see a whole new generation of TVs in the future with this HDR technology built in, and new streaming technologies designed to deliver HDR imagery to match those TVs. Of course it will take more bandwidth, and that’s still a concern, but if you’re really equipped to make everything work, the result should be a level of realism that’s never been seen before.

Image courtesy of Barry Blanchard

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 5,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.