Two Dumb LUT Questions

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Duckpaddle

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Two Dumb LUT Questions

PostWed Jun 02, 2021 5:35 pm

In the base DaVinci Resolve install a number of LUTs are available. Working with the BMD LUTs, I see a number of LUTs like "Blackmagic 4.6K Film to Extended Video v4" and "Blackmagic Pocket 6K Film to Video v4".

Q1) Does "4.6K Film" refer to the raw file (.braw) from either a BMPCC 4K or 6K?
Q2) Is there a difference between the image sensor color response for the BMPCC 4K and a BMPCC 6K?

Thanks in advance for answering what may seem obvious.
Any other tips for decoding the file names would be appreciated.
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Marc Wielage

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Re: Two Dumb LUT Questions

PostThu Jun 03, 2021 6:32 am

Duckpaddle wrote:Q1) Does "4.6K Film" refer to the raw file (.braw) from either a BMPCC 4K or 6K?
Q2) Is there a difference between the image sensor color response for the BMPCC 4K and a BMPCC 6K?

I think the original 4.6K Film LUT was for CinemaDNG files -- or at least that's how I saw it used when making proxy files for editing. I think the color response is different, but it's said to be improved with the later cameras. I can say the newer cameras have less noise overall (all things considered).

You know, it's possible not to use a LUT at all and still color-correct projects shot on Blackmagic or Red or Alexa or whatever you have. It is mandatory to use the manufacturer's color science, and I keep a close eye on the contrast curve and so on early in the correction. Another method is to use an early node for a Color Space Transform, and go from the Input Color Space & Gamma, and Output Color Space & Gamma. You could go from BMPCC 6K -> Rec709 if you wanted to.

Honestly, I've probably done 14-15 Blackmagic feature projects, and I just eyeballed it and used curves and LiftGammaGain and got there by hand -- no LUTs, no transforms, no color management, all just display-referred (but we were only delivering Rec709). The cameras actually look pretty good right out of the box. It does help to take time and experiment. The manual also has lots of useful information. Read the section in the v17 manual starting on p. 149, "Camera Raw Settings -- Blackmagic Raw," and it goes into it in great detail.

Part of the power of Resolve is that it gives you 3 or 4 different ways to correct Raw material. You can do it from scratch, you can do it with Color Management, you can do it with CST nodes, you can do it with LUTs... the basic method is up to you, and there's pros and cons with each method. It does help to shoot a color chart reference with known values -- many use the XRite Color Checker Video, but I'm a bigger fan of the DSC Chroma Du Monde -- and learn how to interpret the values on scopes.
marc wielage, csi • VP/color & workflow • chroma | hollywood
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Ellory Yu

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Re: Two Dumb LUT Questions

PostThu Jun 03, 2021 6:47 am

Like Marc said there are many ways to tackle a grade. I rarely use LUTs but when I do I usually go for style LUTs only after I do much of the braw to REC709 CST. Then I apply a style LUT as my last node. In between the last CST node and the LUT I do my corrections with a bit of the LGG, temp, contrast and sat curves, or just the Raw tab setting to get it to where I like it. I have gathered many style LUTs over the years - like the common orange-teal look for REC709.

I know my response is not answering your questions but offering you other ideas that could work for you.
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Uli Plank

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Re: Two Dumb LUT Questions

PostThu Jun 03, 2021 6:51 am

Q1: Film applies to log recordings in any codec. That said, I second doing it by hand.
LUTs are like instant noodles, grading can get you to pasta by an Italian master chef. But without trying you’ll never get there.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

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Duckpaddle

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Re: Two Dumb LUT Questions

PostThu Jun 03, 2021 12:44 pm

Thanks for the great advice. I have an engineering background but in this space I should be using my Right Brain!
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Howard Roll

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Re: Two Dumb LUT Questions

PostThu Jun 03, 2021 2:37 pm

Duckpaddle wrote:Q1) Does "4.6K Film" refer to the raw file (.braw) from either a BMPCC 4K or 6K?


1. No, that would refer to CDNG shot on the UM46. Could be Gen1 or Gen3. The UMP could shoot Gen3 or Gen4 (.braw). The UMPG2, The Mother of Braw, is Gen4 only.

Duckpaddle wrote:Q2) Is there a difference between the image sensor color response for the BMPCC 4K and a BMPCC 6K?


2. Yes, no. They use the same colorspace, but use a slightly different transfer function.

Good Luck
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John Paines

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Re: Two Dumb LUT Questions

PostThu Jun 03, 2021 3:40 pm

If you're a beginner and don't want to end up with a dog's dinner, use technical LUTs or (better still) color management. There's no shame in it, professionals use these tools as well. The best argument against DIY is reality: all the badly or incorrectly normalized amateur log footage which appears online, worse than you'd get from a point and shoot. There's no obvious means by which you can teach yourself these skills. You can see the result, but not how to get there.
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Marc Wielage

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Re: Two Dumb LUT Questions

PostTue Jun 08, 2021 11:16 am

John Paines wrote:If you're a beginner and don't want to end up with a dog's dinner, use technical LUTs or (better still) color management. There's no shame in it, professionals use these tools as well. The best argument against DIY is reality: all the badly or incorrectly normalized amateur log footage which appears online, worse than you'd get from a point and shoot. There's no obvious means by which you can teach yourself these skills. You can see the result, but not how to get there.

Eh, I just beat on the knobs until I like what I see. Or -- more realistically -- I don't hate what I see.

We occasionally run into "dog's breakfast" projects where you have well-shot material, horrible GoPro shots, bad DSLRs, bad Zoom captures, iPhone material, interspersed with well-shot Red or Alexa or Sony or Blackmagic footage. It's a nightmare to go through it, but a lot of what we do is use Memory stills and the Gallery to quickly recall a look that works, and then move on. C-mode timeline sorting -- where you can immediately group together all the shots from a given camera source -- is another way to do this quickly.
marc wielage, csi • VP/color & workflow • chroma | hollywood

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