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28th March 2022, 04:11 | #1 | Link |
hlg-tools Maintainer
Join Date: Feb 2008
Posts: 413
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Alita: Battle Angel 4K - Help Me Understand the Grading
I have the US UHD release of Alita: Battle Angel. The color grading on this thing seems to be rather interesting. It's much different from my other 4K releases.
In particular: 1. I currently estimate reference white to be at 47 nits. 2. The brightest spot I can find in any frame with light directly into the camera comes in at 53.3% signal level. 3. The credits are the brightest thing in the whole picture at 55.7% signal level. With an understanding of the PQ EOTF: 53.3% -> 128 nits 55.7% -> 162 nits So at the mastered levels on disc: Reference white: 47 nits Direct light: 128 nits Credits: 162 nits Let's scale the linear display brightness to put reference white where SMTPE wants it: Reference white: 100 nits Direct light: 272 nits Credits: 345 nits Or if we bring things up to where the ITU wants them: Reference white: 203 nits Direct light: 553 nits Credits: 700 nits So I have two questions: 1. What is with the reference white level here? I saw in another thread that cinema XYZ masters have reference white at 48 nits. That's awfully close to my rough-eyeball estimate of 47 nits. 2. Why is the dynamic range so freaking poor for HDR10? I've read that cinema puts peak white at 2.7X reference white. That's awfully close to the ratio between my estimated reference white and the direct light going into the camera. It's like this "HDR" grading is just a naive transfer from the cinema master. |
28th March 2022, 17:26 | #4 | Link | |
Broadcast Encoder
Join Date: Nov 2013
Location: Royal Borough of Kensington & Chelsea, UK
Posts: 2,902
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Quote:
I don't have much experience with Dolby Vision myself and I've always ignored the second layer due to the lack of open source decoding options. I wonder if Colorfront Transkoder is able to read it properly and output something... |
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29th March 2022, 15:59 | #5 | Link |
hlg-tools Maintainer
Join Date: Feb 2008
Posts: 413
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I don't know what kind of Dolby Vision it has. There's only one video stream in it, I think.
Although now I'm having thoughts of converting it back to XYZ just because I'm bored. And, well, maybe players will have a better idea of what to do with it. Where's reference white? 0.68 signal level? |
29th March 2022, 21:28 | #6 | Link | |
Life's clearer in 4K UHD
Join Date: Jun 2003
Location: Notts, UK
Posts: 12,227
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Quote:
Also... When the disc was released (back in Jul 2019) it was one of the first to also include HDR10+
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