Top 5 things to know about 4K

There may be some confusion about the term 4K. Tom Merritt offers five things you should know about the video technology.

4K has turned the corner--content is there online and on cable and coming soon over the air--so you can shift your skepticism to 8K for now. 4K is a usable practical video technology--so what is it again? Here are five things to know about 4K.

  1. 4K is a resolution. It's the number of pixels you'll see, and it isn't exactly 4,000. It's four times the pixels you get from 1080p because it's 3840 x 2160. The brand name is Ultra High Def or UHD.
  2. 4K means something different for movies. In movies, 4K means you have a width of 4,096 pixels. Depending on the aspect ratio, you have varying numbers of vertical pixels. The flat crop 1.85:1 aspect ratio allows you to cheat and only do 3,996 pixels across, but it's only four pixels short--that's still way closer than TV.
  3. Wait, why is it called 4K again? Mostly because it sounds cool. For movies, it's straightforward--you have a few more than 4,000 pixels wide. For TVs, I guess it's rounding up on the pixels across--3840. Except 1080p and 720p apply to the vertical pixels, so technically 4K should be 2160p or something.
  4. Did I say something about over the air? Why yes, I did. A broadcast standard called ATSC 3.0 is being marketed under the name "nextgenTV." It will let TV stations broadcast 4K video in HDR with refresh rates up to 120 Hz. The first TV sets capable of receiving ATSC 3.0 or nextgenTV will go on sale this year, and stations in the 40 largest US TV markets are committed to start broadcasting it by the end of the year.
  5. So what's HDR then? Well, that's a whole topic in itself, but in relation to 4K, it's a way to get the most out of all those pixels. Unlike HDR photography, HDR on TV does not combine images to simulate a wider range--HDR on TV actually achieves a wider range. If the content is HDR, then an HDR-capable TV can use the extra pixels to increase contrast and widen the color gamut. And technically, that would be true for 1080p or, heck, even 480p, but in practice, nobody makes that.

So 4K… It's not just a buzzword anymore. In fact, it's the most common option when you go buy a new TV, even a budget one, so it's good to know what it really means. Head back for the 8K version for this in about five years or so.

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Big modern TV with 4k resolutions and young woman on foreground watching some video

Image: iStockphoto/baloon111