What am I missing? (UHD vs Blu-ray)

[blurayGeo]

Home video tech question:


Most new films shot in the digital age are finished at a 2K DI in post-production, if not outright photographed in 2K to begin with; therefore, with UHD Blu-Rays and 4K home video technology, I'd thus originally come to the conclusion that there was absolutely no point in purchasing the UHD disc of a contemporary film that was never even finished in 4K, because it would simply be an upconvert (that most decent-quality players or TVs can do well-enough anyway...for free, without paying the premium price of the UHD disc over the 1080p BluRay disc). However, I have a couple of follow-up thoughts:

First, the latest 4K TVs and projectors practically all have HDR capabilities (nearly all with HDR10, and many more everyday supporting DolbyVision); many UHD releases are graded with HDR; so, would it make sense to purchase a film finished in 2K that was upconverted to 4K on a UHD disc IF and ONLY IF that UHD disc featured HDR (to provided higher luminance contrast and expanded color palette)?

This brings me to my second pondering: I imagine that most theatres, of which 99.9% of project digitally now, must have a projection system of AT LEAST 4K, because some directors will shoot digitally in native 4K or above OR shoot in 35mm and finish with a 4K DI that is sent to the theatres in native 4K (in fact, a lot of these badasses, such as Tarantino and Nolan, have shot and PROJECTED in 70mm in the past five years).


Now, since the theatre projectors are almost certainly 4K or above, I imagine that, just as a 2K-equivalent disc (ie. Blu-Ray) is upconverted on a 4K home display, these 2K films that are sent to the theatres for screenings on 4K+ projectors, they ar eupconverted to 4K.

However, here is the crux of the matter: are these 2K films that are being sent out to theatres already FINISHED with HDR when they are screened theatrically, and thus being PROJECTED with an HDR-capable projector when you head out to see the latest hit superhero epic when it premiers next Friday? Or, is HDR ADDED only after theatrical exhibition for the sake of home video viewing?

If the answer is that films that are being upconverted are still being projected with HDR, then it would technically mean that, even though you're not buying the UHD disc for improved NATIVE resolution, you are getting the color and contrast that was theatrically exhibited; if however, on the other hand, if HDR is only applied to an upconverted 2K film on UHD disc as a post-theatrical-exhibition gimmick, then there truly seems to be NO point, since you're not getting an accurate representation of what was screened theatrically?



What am I missing here, and what is the ultimate answer to this question?

[Geoff D]

A few assumptions & misconceptions to clear up:

4K cinema is still very, very limited in terms of worldwide rollout, a mere 17% of screens according to this article: https://www.screendaily.com/features...124023.article

Movies are still shown in 14fL (about 48-nit) SDR for the most part on those projectors, however they are graded & projected with a wider colour gamut and higher bit-depth than what conventional 8-bit SDR 709 Blu-ray can manage.

There is a limited roll-out of HDR in cinemas from the likes of Dolby who promote their Dolby Vision via the Dolby Cinema chain. This system is different from what's applicable to a home mastering of Dolby Vision (108 nits peak vs 4000 nit peak) but it is still part of the theatrical workflow for most big event movies. So no, it's not something that's being bolted on afterwards but is now being handled upfront, with the subsequent home DV grade using the theatrical decision making as its starting point.

HTH

[Alister_M]

It's not just about pixel counting. A 2K digital intermediate is still a huge file and the heavily compressed home-video transfers will inevitably look better upscaled in 4K with an HEVC encode over a 1080p AVC job.

[StingingVelvet]

Don't discount wide color gamut, which IS more theatrically accurate. I was amazed for example at just how flat and beige Jurassic World 2 looked when I compared it to the UHD. That color improvement can be massive, depending on the title, and there's no accuracy concerns there.

HDR and 4k resolution I can definitely see shrugging your shoulders over if your goal is emulating a theatrical showing, but you might want to give the format a try on good hardware before you write it off. Most of us around here have been made converts simply because the improvements of HDR especially are too good to ignore, accuracy be damned.

[Deciazulado]

The 2K master has full resolution 1080p chroma, while the BD quarters this to 540p x 960.

UHD having 1080p x 1920 chroma keeps the 2K master color resolution. being 4x the color resolution of BD.

BDs are 8-bit gamma 2.X, UHDs are 10 (HDR-10) and 12 (DolbyVision) bits PQ a more efficient tone mapping encoding.

Also UHD can go to 60p, so you can watch for example Billy Lynn's Long Halftime Walk in its 60fps shot frame rate.

[Fang Zei]

Originally Posted by Deciazulado

The 2K master has full resolution 1080p chroma, while the BD quarters this to 540p x 960.

UHD having 1080p x 1920 chroma keeps the 2K master color resolution. being 4x the color resolution of BD.

By this you mean digital cinema’s 4:4:4 color subsampling vs home video’s 4:2:0?

Does UHD still use the 4:2:0 of bd or is it 4:2:2?

[Penton-Man]

Originally Posted by blurayGeo

Most new films shot in the digital age are finished at a 2K DI in post-production, if not outright photographed in 2K to begin with;

The part of which I bolded is news to me. Plus, these days many (Steve Yedlin, etc.) think that due to the super sampling effect (https://www.youtube.com/watch?v=JQdJ4u0UmXo#t=19m43s ) of feature film productions commonly using a ‘4K’, if not ‘8K’ camera for acquisition ends up being of greater significance to picture quality than the finishing spatial resolution.

[Geoff D]

Originally Posted by Fang Zei

By this you mean digital cinema’s 4:4:4 color subsampling vs home video’s 4:2:0?

Does UHD still use the 4:2:0 of bd or is it 4:2:2?

UHD still uses 4:2:0 so it's a quarter of the luma resolution. But what Deci is saying that a quarter of the pixels of 3840x2160 is 1920x1080, i.e. the chroma resolution of UHD is still four times that of regular BD and so you're effectively "seeing" the full chroma of the actual 2K master in the upscaled 4K disc.

I see this effect a LOT when comparing an in-home upscaled BD to the studio-upscaled UHD, the chroma usually resolves a lot more detail in the reds and blues of the image, even if the actual spatial resolution of the images is identical. I took a photo here to demonstrate the effect in Transformers 4: https://forum.blu-ray.com/showthread...n#post14371666

[blurayGeo]

Learned a lot with these responses!!!

So, I remember now about oversampling, like when, even if you shoot in 4K or SCAN in 4K, even if you master in 2K, the oversampling will generally provide a better image in 2K finished product (that explains why people freak out about 'new 4K scans' on films that only get BluRay releases).

You know, I started getting into a lot of this because of sites like realvsfake4k etc. I mean, if a blu is $15 and the UHD is $25, I figured, why pay more if I'm not getting anything more than an upscale, which my player or TV can do for me? I already understood the value of buying 35mm and 70mm in UHD, because of their great resolution.

So, it sounds like, based upon what I'm reading, that it definitely DOEs make sense, for the best quality, to buy UHD releases of 2K masters, EVEN IF IT DOESN'T INCUDE HDR, because you'll be getting the original full-2K color gamut that is basically downgraded on a BluRay disc. Also, a 4K disc will give even a 2K master more 'breathing room' and less likelihood of artifacts, right?

[Alister_M]

Originally Posted by blurayGeo

So, it sounds like, based upon what I'm reading, that it definitely DOEs make sense, for the best quality, to buy UHD releases of 2K masters, EVEN IF IT DOESN'T INCUDE HDR, because you'll be getting the original full-2K color gamut that is basically downgraded on a BluRay disc. Also, a 4K disc will give even a 2K master more 'breathing room' and less likelihood of artifacts, right?

Exactly. You still get a detail uptick from a 2K master upscaled to 4K, in addition to all the color/HDR benefits. Some of the best-looking UHD discs I've seen so far are from 2K masters.

[ROSS.T.G.]

Originally Posted by blurayGeo

Learned a lot with these responses!!!

So, I remember now about oversampling, like when, even if you shoot in 4K or SCAN in 4K, even if you master in 2K, the oversampling will generally provide a better image in 2K finished product (that explains why people freak out about 'new 4K scans' on films that only get BluRay releases).

You know, I started getting into a lot of this because of sites like realvsfake4k etc. I mean, if a blu is $15 and the UHD is $25, I figured, why pay more if I'm not getting anything more than an upscale, which my player or TV can do for me? I already understood the value of buying 35mm and 70mm in UHD, because of their great resolution.

So, it sounds like, based upon what I'm reading, that it definitely DOEs make sense, for the best quality, to buy UHD releases of 2K masters, EVEN IF IT DOESN'T INCUDE HDR, because you'll be getting the original full-2K color gamut that is basically downgraded on a BluRay disc. Also, a 4K disc will give even a 2K master more 'breathing room' and less likelihood of artifacts, right?

The value of buying a UHD that was shot on 35mm is you’ll have resolution that matches film. Don’t overthink it, you’ll be happy you made the jump, I guarantee it or your money back.

[ToEhrIsHuman]

Another point worth mentioning is that 2K is not the same thing as 1080P. 1080P has a 1920 horizontal pixel resolution while 2K is 2048. That 6.7% difference in resolution, while not overwhelming, is not insignificant.

[Staying Salty]

This thread gives a good overview of 4K Blu-rays. Take a look at these reviews. They will help you decide if 4K is right for you.

Ultra HD Blu-ray (4K) Discs and High Dynamic Range (HDR) for Dummies

Specifically:

Dolby Vision Reviews by Geoff D “The Geoffy Vision™, it never lies!”

HDR10 Reviews by Geoff D “The Geoffy Vision™, it never lies!”

[blurayGeo]

Thanks for the help. Oh, I know 4K is right for me, I just wasn't sure whether buying titles with 2k masters on UHD was a waste of money or unfaithful to the original presentation.

[gkolb]

Bump it