4K/UHD update

I wanted to come back to a few old subjects, and we can start with Ultra HD/4K. No point in updating the status of the concept here, that’s certainly done to death elsewhere. I’ve not had hands-on UHD for almost a year, and have a few thoughts.

First, I’ve succumbed to using UHD for the term describing the new higher than 1080p resolution home video format. I used to resist and use 4K, but since UHD isn’t really 4K, that’s over now. UHD’s resolution is below DCI 4K (Digital Cinema Initiative), and by a rather inconvenient amount that doesn’t scale well, but can be cropped. So, yet again, we have the movie industry creating content at a different native aspect ratio that presented on our televisions. How did we get into this mess anyway?

We have Dr. Kerns H. Powers of SMPTE to thank/blame. Back in the 1990s when thought was being given to wider aspect ratio TVs, the question was, of course, how wide? We had US TV at 1.33:1 (4×3), which came from the film industry’s “Academy Standard” of 1.375:1, the aspect ratio of nearly every film made up until the early 1950s. The TV folks reasoned that they’d be able to use all that wonderful material on TV, so it made sense to shape at TV picture tube fairly close to that. 1.33 vs 1.37 is actually a negligible difference, but it’s key to not that there actually was a difference.

But something strange happened. TV drew the audience away from the theater, and the theater immediately saw this by reduced ticket sales. So, knowing they had the big screen in the first place, they made it bigger…wider. In the 1950s, there were a pretty big handful of different wide-screen methods, and the study of wide-screen film formats is the subject of an entire book, “Wide Screen Movies: A History and Filmography of Wide Gauge Filmmaking” by Robert E. Carr and R. M. Hayes, 1988. There are now other books as well, but this was, I believe, the first. However, all the various ratios shook out to just a few, and we ended up with 2.39:1 for anamorphic movies, and 1.85:1 for “flat”, non-anamorphic movies. 1.85:1 was simply a cropping down of 1.37, now known as full frame or full aperture. The cropping could be either “hard matte”, printed on the film that way, or cropped in the projector by the aperture plate. Many films were shot full frame, and release that way, though theaters used the cropped aperture plate anyway. The reason was, the full frame made it easy to transfer to TV!

So, by the mid 1950s we had the movie industry creating content that wouldn’t fit TV well. 2.39:1 on a 1.33 TV is a horrible mess. You either “letterbox” it and end up with far less vertical resolution, or you “pan and scan” each scene so the main action is in the TV frame. Neither works well.

So in the early 1990s, with several HDTV demonstrations already being done, it made sense that SMPTE would want to lock down the aspect ratio for the foreseeable future. But what do do in the transition? We’d now have TV content AND movie content that wouldn’t fit most TVs in the world. That was a self-limiting condition, of course, as at some point old TVs would mostly go away. But then we had the back-catalog of every TV show ever made, but now played on new TVs with a wider aspect ratio. What to do, what to do. There was clearly going to be a compromise.

The choice, it turns out was to make the new TV aspect ratio the geometric mean between the narrowest and the widest aspect ratios of 1.33:1 and (now, note this figure carefully!)2.35:1. That works out to 1.77:1. Bingo. Done. Except, it wasn’t.

That nice new perfect geometric compromise did something really weird. It made every existing format at least a bit incompatible. There was NO 1.77/16:9 material anywhere. And as far as the film boys go, there would never be. They’ve been quite happy with 1.85:1 for decades, and 2.39:1 for anamorphic, and 2.20:1 for 70mm flat, IMAX at 1:43, or 1.9, or whatever the dome was. At least, that’s where things sort of ended up by the early 1990s and later. Yet, TV was now 16:9, and nothing fits that without something being a bit wrong. Old 1.33 material is either pillar-boxed with blank side panels, or (Ugh!) stretched to fit. 1.85 films are cropped, 2.39 films are letterboxed, and HDTV original material fits perfectly. Now the moment I heard the SMPTE’s decision, I asked myself why on earth would we NOT do 1.85? We still compromise the extremes, but at least we have thousands of films that exactly fit, and new material would fit too. Frankly, I’ve always felt wider was better anyway.

So now, we have TV’s staunch and unique 16:9, and film’s staunch and not-so-unique 1.85 and 2.39 with resolutions respectfully rounded down from the actual figures to 2K and 4K. Along comes digits. The Digital Cinema Initiative chose to stay with the basics, and not change anything. But we did force everyone on earth to change to a digital TV, right? Sorta? That’s 16:9. Then we bumped from 1080p at 16:9 to UHD. Of course, we couldn’t and wouldn’t change the shape of the screen now, right? We’re “stuck” with 16:9, so UHD (disrespectfully rounded UP to 4K) is still that. SO, part of what makes DCI 4K different from consumer 4K is the aspect ratio. The other part is the dimensions of the actual pixel grid, which, according to Joe Kane, simply don’t scale well to each other. So the dimensions AND the aspect ratio difference is fixed by cropping the original DCI frame down to UHD. Cropping? That means trowing away the edges. Those would be the edges the Director of Photography and the Camera Operator pay pretty close attention to in composing each shot.

So it’s a compromise, and I think, a poor one. The choice was a geometric mean between extremes, when it probably should have weighted 1.85 and 2.39 (not 2.35) much more, un-weighted 4:3, as at some point, there would be no more of that made. Personally, at our house we watch a lot of 4:3. We love old movies, and some of our favorite SciFi is Star Trek, all shot 4:3. It’s nice to see some shows that were shot on film remastered in HD, but as much as I like Friends to fill my screen, I wonder what I’m missing. I’ll live with the 4:3 in the middle of my screen with the blank side panels, thanks. I’ll never stretch anything.

Solutions? Not really. Scaling DCI 2K and 4K to 1080p without cropping can, and is done quite well. Cropping DCI 4K to UHD on Blu-ray? Just seems wrong, the result of 25 year-old, ill-conceived compromise.

So, I’m now calling it UHD.  I’m not calling it 4K.  And I LOVE my UHD TV.  It does a lot of really nice things for 1080p content.  What little UHD I’ve thrown to it, it’s handled well.  It’s internal scaling of 1080p to 4K, especially with still images, is spectacular.  I’m still in color space Rec. 709, but that’s life.  I didn’t think I’d be saying this, but UHD TVs actually do look better than 1080p, even at a viewing distance where it shouldn’t matter.

More on that another time.

Leave a Reply