On-set monitoring

[Willian_Aleman]

@nick

No. The IDT always comes first. It is the Input Device Transform, and is what takes the image from it’s native colour space into ACES.

Nick, thanks for the details in the response.

My assumption was based in that in Davinci Resolve the order of operations was that by selecting, Davinci Resolve Master, Project Settings <Color Science<, came first, in this order:

1 - Color Science: Turning on ACES selection, (ACEScc or ACEScct)
2 - IDT
3 - Color Management, ACES Input Transform
4 - Look Grade
5 - RRT
5- ACES Output (ODT) Transform.

Really, the step by step the user needs to go in DR for ACES, made me think that the >Color Science< ACES selection setting came before the IDT.

Thanks for clarifying the order of operations.

[CharlesBoileau]

It seems to work very well. A slight shift in hue (more reds in the skin tones in ACES) in one look I tested but nothing critical… Just to resume here is what I did

In Resolve

• Added a LOGc image
• Turned on ACEScct (with IDT and ODT as usual)
• Built a grade
• Added 2 nodes before the grade
• Node 1: LOGc IDT DCTL
• Node 2: ACES to ACEScct DCTL
• Exported a LUT
• Switched back to YRGB added the LUT and compared with the ACEAcct still/look.

Does this seem correct @nick
And, will this work with the SLOG3 IDT?

Thanks!

[nick (Nick Shaw)]

@CharlesBoileau

Does this seem correct @nickAnd, will this work with the SLOG3 IDT?

Yes and yes.

Is the difference you see just of the order of magnitude you expect from a LUT approximation, rather than a proper ACES implementation?

[Willian_Aleman]

@nick

And that’s without any LMT, such as a “show LUT”, which if implemented as per spec should go between steps 4 and 5.

Although I haven’t worked yet with LMT yet, (I believe a few are) if the LMT is part of the creative process, why is it that in the other of operations you have placed the LMT between step 4 and 5 and not between 2 and 3 or as an inclusive first item of step 3? Specially if it’s going to be used as a show LUT. I suppose that all further changes made on-set by the DIT should come after the show LUT, not before. Could you please elaborate on this? Thanks!

[nick (Nick Shaw)]

@Willian_Aleman

…why is it that in the other of operations you have placed the LMT between step 4 and 5 and not between 2 and 3 or as an inclusive first item of step 3?

Because if you read TB-2014-010.pdf on this page, you will see that an LMT goes after the grade and before the RRT, and is applied to linear ACES data. An LMT modifies the look imparted by the RRT.

However I did say “if implemented per spec”, since the term LMT gets used more loosely to mean any fixed part of the grade which is not modified on a per shot basis.

[Willian_Aleman]

@nick

Because if you read TB-2014-010.pdf on this page, you will see that an LMT goes after the grade and before the RRT, and is applied to linear ACES data. An LMT modifies the look imparted by the RRT.

Nick, thanks for pointing out the reading.
I did review the charts appearing in the TB-2014-010, Design, Integration and Use of ACES LMTs.
Thanks a lot for the clarification.

Since Davinci Resolve supports now LMT, I’m going to start experimenting with it.
Hum! I’ll probably better wait for the upcoming release of Scott Dyer article, LMTs Part 2.

[nick (Nick Shaw)]

@CharlesBoileau

Personally, I’d really like to get the Log3g10/RedwidegamutRGB IDT.

I have now added that IDT to the DCTLs on my website.

[CharlesBoileau]

Sorry for the late reply. I was grading for the last week…

@nick. I’m not sure I understand your question. But what I’M seeing is a slight shift in reds. IE: the ACES version a more reddish appearance to skintones etc… But, it’s very soft. I don’t think any DP could even see this when going back to ACES once in color grading.

When looking at your question I guess I could say it’s a little bit of both. It’s the lack of proper implementation for these types workflows and possibly the LUT approximation…

Makes sense?

[nick (Nick Shaw)]

I was just referring to the fact that a LUT is a way of approximating a transform (which works very efficiently in hardware) but it can never be perfect, because some values are interpolated. Whether the inaccuracies are noticeable depends on the transform and the image.

Since you say that what you are seeing is subtle, it is probably caused by this.

[JamesMilne]

Hello Willian et al,

If I may introduced myself, I’m the lead developer on the FilmLight Prelight software.

It is in fact possible to get metadata for shots (CDL SOP & SAT, tape, clip, scene, take, comment, etc) out of Prelight via ALE, which can be used to import the values into other systems.

You can also use Prelight to generate IDT and LMT+RRT+ODT LUTs in a vareity of formats, which allows colour corrections created into Prelight to be used in other systems. We are currently working on finishing up this part of our export code, so that you can generate ALE, CDL and cubes in one hit as a package.

Obviously there are advantages to using BLGs if you are working in a FilmLight ecosystem, but we want Prelight to be able to work standalone also.

Regards
James Milne
FilmLight Ltd.

[Willian_Aleman]

@JamesMilne

You can also use Prelight to generate IDT and LMT+RRT+ODT LUTs in a vareity of formats, which allows colour corrections created into Prelight to be used in other systems. We are currently working on finishing up this part of our export code, so that you can generate ALE, CDL and cubes in one hit as a package.

Hello James,

Thanks for the update in the development of Prelight. I’m currently running the beta version.
It’s welcomed news to know that Prelight can be used as a stand alone color management and creative grading on-set application.
I’m pretty sure that for DITs and cinematographers, the ability to create IDTs in preproduction is a welcome news, specially for camera considered under a -generic- status, because the absence of manufactures providing their own IDTs.

I’m definitely looking forward to the final commercial release of Prelight.

[CharlesBoileau]

@JamesMilne. Thanks for the offer! can Prelight write to CLF (XML) format?

[JamesMilne]

Hi Charles,

I’m not familiar with “CLF” format.
What software reads/writes those files?

Regards
James Milne
FilmLight Ltd.

[nick (Nick Shaw)]

@JamesMilne

I’m not familiar with “CLF” format.
What software reads/writes those files?

Common LUT Format. Documentation is on the ACES documents page (S-2014-006).

Support for this format is supposedly required for ACES compliance, although until recently it was rare. AutoDesk have been the biggest supporter, and have added some extensions of their own (not sure how I feel about adding non-standard extensions to a “common” format). I understand that Resolve has also added support in the v14 beta.

[CharlesBoileau]

HI @JamesMilne! Sorry for the late reply… I was on vacation.

The CLF (common lut format) format is a sort of XML that’s now supported by Resolve. And I think it’s what the ACES people are pushing for the LMTs.

If we could export a CLF from Prelight we could use streamline your software with Resolve in a full non destructive ACES workflow. That would be very cool…

As of right now. I cannot make a “emulation” LUT for a ACES based look for a camera and have that look exported to CLF to be used afterwards in the color pipeline.

Cheers!

[jgentry (Jonathan Gentry)]

I’m trying to use Resolve Live to monitor in ACES. The setup is URSA Mini Pro - BM Mini Recorder - MacBook Pro - Resolve set up with ACES in ColorManagement - BM Mini Monitor - FSI Monitor

The image is way over saturated and red. I called Resolve support and received this response:

Hello,

It is more of a feature request than a bug. A bug implies that a feature does not work as designed. Resolve Live was not designed to work with ACES, it was designed to be used with DaVinci YRGB and LUTs.

All the Best,
Tyler Deary
Technical Support Representative
Blackmagic Design Inc.

[CharlesBoileau]

Unfortunately, I don’t think that is possible. The IDTs for URSAs are not published.