Optimal output format for 4K. . .

[Stephen Pruitt]

This isn't exactly about cinematography, but it's related, so I thought I'd try here first.

Say you want to shoot something in 5K, but release it in 4K. There are two 4K horizontal dimensions: UHD (3840) or true 4K (4096)

Is one preferable than the other for your final output file?

Obviously, oversampling is generally preferable to not, but since the differences are so slight between 4096 and 3840, I thought it would be best to inquire before I go further.

Thanks.

Stephen

[Patrick Tresch]

I do 4k DCI full container for cinema use and UHD for web use.

[Blair S. Paulsen]

FWIW, 3840 is more widely supported by post tools, monitors, steaming services, etc. Unless there's a specific reason to go 4096 DCI, I'd avoid it.

Cheers - #19

[Marc Wielage]

I agree with Blair above. We generally tell our clients, "get your delivery specs from your distributor, figure out where you need to end up, and that dictates the workflow to get you there."

Amazon, Apple, CBS All-Access, Disney+, HBO Max, Hulu, and Netflix generally request 3840x2160, but it of course depends on your intended aspect ratio. (I'm not sure of Peacock's specs since they're so new.) Brad Allen has a terrific Aspect Ratio chart at this link:

https://www.unravel.com.au/aspect-ratio-cheat-sheet

These are his specs for UHD/streaming/home video:



3840x1920 seems to be the new "prestige" format (2.00:1) for a lot of high-end TV shows like Westworld, Star Trek and so on. Note that show is about $14M-$15M per episode. I think 2.00 is a good compromise between traditional 1.78 HD and 2.39 scope, but of course you have to frame for it on set and in post. There are also certain channels that request a full-frame 1.78 version, essentially a tilt & scan version, and it's a delivery requirement that is a necessary chore to deal with. Note also that most of these services now request HDR/Dolby Vision as well, which is a whole different set of headaches (and cost).

[Stephen Pruitt]

Interesting, Mr. Wielage. . . especially since my preferred aspect ratio has always been 2:1.

:-)

Thanks much for all your help gents!

Stephen

[Björn Benckert]

Yes I would downasmaple striaght to UHD 3840 width. AS there is so few screenings that actually do 4096. And its not good to go from 8k to for example to 4096 and then do an additional small downscale / sample.

And trough the whole post chain things simply is way more comfy at 3840 as very few sit with 4096 screens. But quite a few now work with UHD TVs and computer screeens.

[Patrick Tresch]

16:9 is a tv format. If you shoot for tv go this format.
When I shoot for DCP theater release, I go to the 1.90 format. It's what replaced the 1.85 film projection aspect ratio.
It's the so called "full container" format. Wich is what DCI created for digital projection in theater.

[Michael Lindsay]

Stephen

Youtube and Vimeo are pretty agnostic and I have been delivering lots of diffent 4k aspect ratios recently.. what I would say to add to Björn's piont is that I have stopped outputing true 4k width film assets bound for online channels as I noticed that it looked a bit edgy/brittle whern viewed on QHD TVs even when sharpenng is turned off... as there is cheap on the fly downsampling happening (I think)...

[Phil Holland]

Take this answer as somebody who's been involved with digital cinema, streaming, and "weirder things".

Most content is produced for a 16:9 or 1.78:1 container. This is known at HD, UHD, and in Japan potentially SHV.

In which case you should be looking at a max width and height of:
- 1080p = 1920x1080
- 2160p = 3840x2160
- 4320p = 7680x4320


If you are producing work for cinema application, yes, the maximum aspect ratio is 1.9:1 approximately. This is known as DCI or DCI Full.

In which case you should be looking at a max width and height of:
- 2K = 2048x1080
- 4K = 4096x2160
- 8K = 8192x4320


That's where that brief crying about real 4K or UHD 4K came from for a little while there.

DCI in particular does have some hard specs for DCI Scope, widescreen, which comes out to an aspect ration of 2.39:1. Also DCI Flat exists as 1.85:1 which was a super popular cinema ratio for many years.


Digital steaming has opened up Pandora's box, erm...., creative possibilities to go off script from standard or well known aspect ratios. For instance if you saw some of my widescreen content produced for Sharp many years ago to showcase 4K televisions, I really enjoyed using 2.2:1, which has a history in the film world, but not so common in the digital world until Mindhunters recently.

Exhibition work has been a mine field of different aspect ratios and finishing resolutions. It's pretty much the only space I've masted for weird 6K, 12K, 16K, and other resolutions as well as really unusual aspect ratios. Did some 5K and 6K stuff to show off some desktop monitors a while back, but that is just when the odd duck display comes on that front. Cool, but likely never going to be an in home consumer standard.


And if you don't want to read all that, TL;DR:

General advice, I would say safely if you aren't ever targeting cinema finishing to something 16:9 or within the 16:9 container is the safest route.

And if you're curious even for cinema, 16:9 makes up most screens in the world and because they fit within the DCI container it's not entirely new to see films actually projected in that ratio as well these days.

[Stephen Pruitt]

Pandora's box, indeed.

I think what I'm going to do is edit on 4096x2048 timeline (2:1. . . since it's my favorite aspect ratio), and then just let Premiere Pro choke it down using letter-boxing as needed. The PBS stations that are showing our films seem fine with a slightly letter-boxed 1920x1080.

Thanks for the help, gentlemen!

Stephen