4K UHD Blu-ray to DCP for playback on 2K commercial projector?

Anything and everything to do with DCP-o-matic.
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ivankjt
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Joined: Sun Apr 25, 2021 9:47 pm

4K UHD Blu-ray to DCP for playback on 2K commercial projector?

Post by ivankjt »

Hi folks,

I've been renting space at a local theater chain just to screen my favorite films on their setup (has always been a dream of mine, besides having my own personal dedicated theater of course).

What I've been doing is converting my own Blu-rays to DCP via DCP-o-matic. The DCP's are then ingested by the theater's server for native playback on their projectors. The theater uses 2K Christie projectors (unsure of the exact model).

My question is, should I even bother using 4K UHD Blu-rays as the source when creating my DCPs, since the projectors are 2K?

Would using 4K UHD Blu-rays rather than standard 1080p Blu-ray as the source for my DCPs result in better quality in the details, grain, etc because of the higher bitrate? I understand there are also things like HDR > SDR conversion which come into play and that may introduce more problems instead.

If anyone has experience converting 4K HDR Blu-rays into DCP - I would really appreciate tips and/or guidance.
Carsten
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Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: 4K UHD Blu-ray to DCP for playback on 2K commercial projector?

Post by Carsten »

It would be interesting to compare a standard BD with an UHD conversion of the same title. I am not exactly sure if all UHD are color coded the same. I would assume that the conversion from BT.2020 incl. dynamic metadata to EDR is the weakest point currently. Digital Cinema is not SDR, but 'EDR' ;-)

I have recently watched a Netflix HDR production in it's SDR playout version. It was watchable, but sucked once I noticed what was going on.
Squidmaster7
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Joined: Tue Jun 23, 2020 9:33 pm

Re: 4K UHD Blu-ray to DCP for playback on 2K commercial projector?

Post by Squidmaster7 »

I think theoretically yes using the UHD version would be better but Im not sure how well DOM handles converting REC. 2020 to P3 (I think thats whats going on). I think youre more likely to introduce errors and would just stick the regular HD files for now until someone more knowledgeable can chime in.
Carsten
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Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: 4K UHD Blu-ray to DCP for playback on 2K commercial projector?

Post by Carsten »

I'd be interested in doing some tests, as we do have a high contrast projector, but, I would first need to get an UHD capable disc reader.
Antti N
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Joined: Mon Nov 16, 2020 5:03 pm

Re: 4K UHD Blu-ray to DCP for playback on 2K commercial projector?

Post by Antti N »

ivankjt wrote: Sun Apr 25, 2021 9:57 pmWould using 4K UHD Blu-rays rather than standard 1080p Blu-ray as the source for my DCPs result in better quality in the details, grain, etc because of the higher bitrate? I understand there are also things like HDR > SDR conversion which come into play and that may introduce more problems instead.
After doing some rather extensive testing with HDR UHD Blu-Rays recently, this was exactly the conclusion that I came to... The reason being that:
Carsten wrote: Mon Apr 26, 2021 1:25 pmthe conversion from BT.2020 incl. dynamic metadata to EDR is the weakest point currently.
I guess that to do the color space downconversion properly, you'd have to play the disc on a UHD Blu-Ray player, have its hardware handle the SDR conversion in real-time according to the HDR metadata, hook the player up to some kind of a HDMI capture device (bypassing HDCP first of course) and then record the downconverted SDR video, ideally to something like ProRes 4444. Even with such a setup you'd still probably only get Rec. 709, not P3, but at least you'd get the "official" SDR image as intended by the color grader.

That being said, apparently there are some UHD Blu-Ray releases that are not HDR. I suppose that those would be plain old Rec. 709 then, so converting them to DCP would be no different than from traditional Blu-Rays.
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