Rec. 2020

ITU: Sounds nerdy, doesn’t it? Rec. 2020 is what display geeks say when they are referring to BT.2020, which is International Telecommunication Union (ITU) Recommendation BT.2020. That last part is a mouth full, but we like simple, so that’s why it’s just Rec. 2020. What are the good people at ITU recommending with Rec. 2020 exactly? I won’t go through everything, but here is a short list:

  • Resolution1: 3840×2160 (4K), 7680×4320 (8K)
  • Frame Rate: 120p (and lower)
  • Bit Depth Per Pixel: 10 or 12
  • Color Space: 75.8% of CIE 1931
  • Primary Color Wavelength: 630nm (red), 532nm (green), 467nm (blue)

3840×2160 (4K) and 7680×4320 (8K) are simple enough, but these pixel formats translate into an aspect ratio of 16:9. I think ITU recommended the wrong pixel format for 8K: really big displays will morph from 16:9 to 21:9. We will watch more film (movies) on massive screens and those fit better on a 21:9 screen.

120p just means 120 frames per second, progressively scanned. No more interlaced scanning. Good riddance. 120p sounds like a great idea, but we might not like it. My client flew in for SID DisplayWeek (thankfully it was held in San Jose this year) and we hopped on over to Magnolia to check out the displays there. What we saw was that movies in 24p looked great. Movies at higher frame rates looked terrible. This was the same issue with Peter Jackson’s The Hobbit: An Unexpected Journey. There are three versions of the movie: 3D HFR, standard 3D, and 2D. HFR stands for High Frame Rate, and in the case of The Hobbit it is 48fps, twice the normal rate of 24fps. I went to see it and I didn’t like it. Vincent Laforet didn’t like it either:

I had absolutely NO CONNECTION with the story. I didn’t identify with the characters at all. I didn’t care about them. I didn’t listen as carefully to they were saying or how they felt. And more importantly I didn’t feel ANYTHING.

But it’s not just me or Laforet, there’s a bunch of others who didn’t like the HFR version of The Hobbit. So imagine what 120p might be like.

75.8% of the CIE 1931 color space. That sounds small, but Rec. 709 (an older recommendation) only covers 35.9% of CIE 1931. 3M and Nanosys showcased a monitor with 93.7% Rec. 2020 color space at SID DisplayWeek. Nanosys makes quantum dots; the best thing about quantum dots is the narrow spectrum of primary colors that make them more pure. Red is more red, and blue is more blue. The colors were quite vivid, but display geeks will need to make sure colors look accurate to our finicky human visual system.

The good people at ITU want a great viewing experience, and it shows with what they have recommended in Rec. 2020. But let’s make sure we go beyond merely meeting Rec. 2020 on a software and hardware level and work toward achieving a higher goal of digitally recreating our world as best as we can so our visual experience is that much truer and richer.

  1. Resolution. We take words and put meaning into them all the time. But sometimes we put the wrong meaning into them; resolution is one of them. Resolution is a measure of density. Let me give you an example. Let’s say there are 100 pixels in a square inch. The resolution would be 100 pixels per square inch. But the display geeks (or was it the display marketing people?) injected the wrong meaning into resolution. When someone asks “What is the resolution of that TV?” A display geek would answer “1920×1080.” That’s wrong. A display geek should know better, and say “The diagonal size is 50 inches. The aspect ratio is 16:9. Which means the area is about 1068 square inches. There’s a total of about 2 million pixels, so the resolution should be roughly 44 pixels per square inch.” 44 ppi is the answer. Then what is 1920×1080? It’s a pixel format.