How are film masters scaled to UHD bluray - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 5 Old 03-14-2019, 04:21 PM - Thread Starter
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How are film masters scaled to UHD bluray

Say you have a 4096 x 1716 film master. It seems to me that the best way to release said content on a 3840 x 2160 bluray would be by cropping 256 pixels horizontally and adding letterboxes vertically. UHD blurays don't come in 3840x1716 (2.24:1) resolution so they are obviously doing something else.

Also what is the purpose of 4096x2160 projectors when there isn't even content available to them. To take advantage of the extra horizontal space, you will have to scale the image so that the pixels are no longer 1:1 with the blu-ray source
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post #2 of 5 Old 03-15-2019, 04:35 AM
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Quote:
Originally Posted by olqxqipz View Post
Say you have a 4096 x 1716 film master. It seems to me that the best way to release said content on a 3840 x 2160 bluray would be by cropping 256 pixels horizontally and adding letterboxes vertically. UHD blurays don't come in 3840x1716 (2.24:1) resolution so they are obviously doing something else.

Also what is the purpose of 4096x2160 projectors when there isn't even content available to them. To take advantage of the extra horizontal space, you will have to scale the image so that the pixels are no longer 1:1 with the blu-ray source
Have you heard of the concept of "safe" in filming? Action-safe, title-safe, broadcast-safe, etc. Basically, movies and TV are shot with extra padding, as it were, to allow for distribution/broadcast in a variety of aspect ratios. Likewise, it's also very useful in editing just in case a boom mic drops into frame or you want to digitally pan/shake/zoom. So cropping the sides (pillarboxing) or the top and bottom (letterboxing) are possible without losing anything important. Between cropping and scaling (up or down), there's a lot of flexibility there to deliver very specific specs to each release, whether the target is theatrical, home video, trailers, streaming...

Keep in mind that Hollywood-industry scaling techniques using the raw master files (12-bit+ 4:4:4) are much more sophisticated than what comes on our televisions, so a studio can achieve very good results if the AR is fixed due to artistic reasons. Likewise, displays with native 4096 can scale the image up (usually with some loss in detail) or it can simply display 1:1 and you'll get a narrow black mask around the whole image.
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post #3 of 5 Old 03-17-2019, 10:17 AM
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It depends on the film, its aspect ratio, and who is doing the transfer.


I had an opportunity to compare some Marvel movies from their DCP to the Blu-ray. One of the 2.35:1 films was simply cropped from theatrical 2K down to 1920x1080 for the Blu-ray. The Avengers was 1.85:1 on theatrical and the Blu-ray was expanded to 16:9. So the Blu-ray actually had more picture while the theatrical was cropped. I believe on the UHD they cropped it back to 1.85:1 again.

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post #4 of 5 Old 03-18-2019, 10:19 PM
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Originally Posted by bryantc View Post
It depends on the film, its aspect ratio, and who is doing the transfer.


I had an opportunity to compare some Marvel movies from their DCP to the Blu-ray. One of the 2.35:1 films was simply cropped from theatrical 2K down to 1920x1080 for the Blu-ray. The Avengers was 1.85:1 on theatrical and the Blu-ray was expanded to 16:9. So the Blu-ray actually had more picture while the theatrical was cropped. I believe on the UHD they cropped it back to 1.85:1 again.
I don't understand why in the case of the Blu-ray being opened up to 16:9 as to why that's acceptable. I want to see the ratio displayed at the theatre also on the home presentation. To me, anything other than the OAR is non theatrical.

Movies must be OAR, sports and movies must also have 5.1 audio, No EE or NO SALE!
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post #5 of 5 Old 03-07-2020, 09:57 PM
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I hope this really answers your question. First off, the ratio of 4096 x 1716 that your talking about is simply a standard ratio of 2.39:1. More about that later.

Blu-rays standard pixel resolution is 1920×1080 (which is the ratio of 16x9 or 1.78:1)
Ultra HD Blu-ray's standard pixel resolution is 3840 × 2160 (which also has the ratio of 16x9 or 1.78:1)

Notice, both have different pixel counts, but the ratio on both are the same.

2K Digital Cinema has a standard pixel resolution of 2048 x 1080 (with a ratio of 1.90:1)
4K Digital Cinema has a standard pixel resolution of 4096 x 2160 (with a ratio of 1.90:1)

Again notice, different pixel counts, but the ratio on both are the same.

The only difference between the two pixel counts between Standard Blu-ray and Ultra HD Blu-ray is the Ultra HD Blu-ray is capable of higher resolution.
The only difference between the two pixel counts between 2K Digital Cinema and 4K Digital Cinema is the 4K Digital Cinema is capable of higher resolution.

Today's motion picture digital cameras are capable of capturing live action at 3K, 4K and 6K, but most of these movies are still finished in 2K for distribution (and even worse, those same 2K masters are also used for Ultra HD Blu-ray releases...at least film can be scanned at 4K for Ultra HD Blu-ray releases.)

Regardless of what resolution live action is captured at, the decision as to what ratio a movie will be presented in is up (I think) to the director, who has the choice of choosing if the movie will be presented in 1.85:1, 2:1, 2.39:1, 1:66:1, 1.37:1 etc. A lot of this depends on the type of movie, and the experience the director wants to portray to movie audiences.

Regardless if a movie is presented on Blu-ray, Ultra HD Blu-ray, 2K Digital or 4K Digital; the thing to keep in mind is what ever ratio the movie is being presented in, only the area being used to display the image will be utilized to create the final result.

Now to get to what I think is the answer to your question. A movie presented in 4K Digital Cinema (which has a pixel count of 4096 x 2160 with the ratio of 1.90:1) only uses 4096 x 1716 of those pixels to create the desired image of 2.39:1.

About the 2nd part of your question. I don't know what the purpose of 4096 x 2160 pixel count on 4K projectors is about, except I can guess it could be a manufacturing limitation such as a chip of that ratio has to be produced to get a certain technical desired result, or (or least likely) if a director want's to present a movie in 1.90:1, 2K and 4K Digital Cinemas apparently could very easily handle that ratio without compromise. And by the way so can Ultra HD Blu-ray, Blu-ray, DVD (and VHS as far as ratio is concerned.)

I just thought of something and of course I'm guessing. 1.90:1 is very close to 1.85:1. It's possible to achieve good results without any defective areas around the edges of the chip (or chips,) a 1.90:1 projector would be more likely to produce flawless 1.85:1 images.



Quote:
Originally Posted by olqxqipz View Post
Say you have a 4096 x 1716 film master. It seems to me that the best way to release said content on a 3840 x 2160 bluray would be by cropping 256 pixels horizontally and adding letterboxes vertically. UHD blurays don't come in 3840x1716 (2.24:1) resolution so they are obviously doing something else.

Also what is the purpose of 4096x2160 projectors when there isn't even content available to them. To take advantage of the extra horizontal space, you will have to scale the image so that the pixels are no longer 1:1 with the blu-ray source

Movies must be OAR, sports and movies must also have 5.1 audio, No EE or NO SALE!
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