Author Topic: Urgent confusion re. log curves  (Read 974 times)

saf34

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Urgent confusion re. log curves
« on: April 25, 2021, 12:02:27 PM »
Hi guys, am hoping you might be able to help me out with my confusion.  I've been asked to send over a heap of footage in log prores 4444 to a grading house (huge shock).  It's currently in DNG form (converted from Canon 5d mk iii MLV) and I'd been editing in Resolve in Rec7090.

What is a safe way to get my timeline nicely output as log without losing data?  I was happily working in Rec709 until this bombshell hit, but now I'm confused about curves and color-spaces.

Specifically: can I import my DNGs into Rec709 in Resolve and not lose data (aren't we in 32 bit at this point?) - and then use Color Space Transform to output some log space version (BlackMagic Cinema-camera film Gen 4 for example?) 

Or should I go into the Blackmagic Film space first (but then which transform to use?  The output as is looks suspicious)

Any help would be really appreciated.  I have to send this out on a drive tomorrow...

Thanks in advance,
Saf34

crzor

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Re: Urgent confusion re. log curves
« Reply #1 on: April 27, 2021, 01:43:45 PM »
I'm by far no Pro at Resolve so take anything I say with a grain of salt.

That being said, did they say which log they expect? You didn't shoot in log so I'm not quite sure why they'd need it. Cinelog maybe? LogC?

I'm confused because, in a color managed workflow, as I would expect from a grading house, it's really trivial to integrate any color space as long as you know which one the footage is in. If they prefer working in Log that's fine, but it's literally two clicks to check the input color space on the footage and it gets transformed into the working color space. So I'm not quite sure if there isn't some misunderstanding between you and the post house.

Anyway, you can do it yourself if you know which color space they expect. Change your Project Settings, Color Management to Davinci YRGB Color Managed and then you change the Output Color Space to whatever. Simplest way to do different Deliveries I'd say.

EDIT: I just now saw, that you already had to deliver the footage :D

What did you end up doing?

allemyr

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Re: Urgent confusion re. log curves
« Reply #2 on: April 27, 2021, 02:53:41 PM »
I think the best you can do is to send them lossless DNG files. If they dont specify what type of LOG its impossible for you since there is so many LOG, Canon/Arri/Sony/BMD-LOG and soo on.

allemyr

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Re: Urgent confusion re. log curves
« Reply #3 on: April 27, 2021, 02:54:49 PM »
If it is 16-bit files I would raise white level before you send them over to max which is 16383 and with standard black level. You can easily adjust that in MLVapp.

saf34

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Re: Urgent confusion re. log curves
« Reply #4 on: May 08, 2021, 12:39:49 PM »
Hi guys, thanks for the replies.  I'll put down my experience here, just in case it is useful to anyone else. 

First thing to say: I think they found Magic Lantern a bit confusing.  I delivered footage both as DNGs and Cinelog-C (using Adobe Camera Reader and the 5D mk iii Cinelog-C log profile).  They looked at both, and preferred as a rule to go with the DNGs just for being closer to source.  It was filmed at 1250 ISO @ 2.8 in low light, so there was only around 9EV dynamic range I think - so from their point of view I think they just saw it as 8-bit footage from an 8-bit camera really.  The best looking DNGs I found to be with 3x3 CS and aggressive bad pixel fixing, so I did this first.

The PITA was actually all with the NLE in Resolve.  I used Resolve for the first time for this, downloading v17.  I did the editing before I knew it would be graded, and so when we got in touch I found out they were on v16.  Fine, but I'd been editing in multicam objects and doing manual sync using retimes.  Then I discovered that you can't export the retimes.  Nor can you flatten a multicam clip if you've retimed it.  So no EDLs, now XMLs.  I could relink all the media to the Cinelog files instead of the DNGs and export a cinelog preconformed, but in the end they just installed Resolve 17 for me which was pretty accomodating...

EDIT: to answer "why log", basically they wanted a preconformed version in case they couldn't recreate any effects (stabilization, retimes, zooms, translations).  So in future I'll probably make sure to render down some cinelog masters from the get-go too

So if it wasn't for the mistakes with the NLE I made it would all have been fine basically!





allemyr

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Re: Urgent confusion re. log curves
« Reply #5 on: May 08, 2021, 05:13:50 PM »
They have Cinelog themselves?

saf34

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Re: Urgent confusion re. log curves
« Reply #6 on: May 08, 2021, 08:00:17 PM »
No, they didn't

allemyr

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Re: Urgent confusion re. log curves
« Reply #7 on: May 10, 2021, 01:59:28 PM »
I think you missed the point and workflow with different LOGs. The point and workflow is, LOG takes less space as you know but if you send them in Arri LOG for example they have to apply ARRI LOG when working with it, they can't apply BMD Film LOG on it for example. This hole thing sounds like a mess with colors.

And the graded end result doesnt look anything close to this i guess: https://www.magiclantern.fm/forum/index.php?topic=25312.0

ISO 1250 isnt very high for the 5D3. Even at 3200 you can have good result with some slight color noise reduction.


saf34

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Re: Urgent confusion re. log curves
« Reply #8 on: May 10, 2021, 07:25:56 PM »
Thanks for this - I'm certainly confusing myself with their unspecified log request, but on I think I'm okay re the Cinelog workflow.  The point of showing them the Cinelog-C was that if they wanted to use that source I'd have bought a second licence and given them a LUT to use to import.  The footage is good- our home grade using Cinelog LUTs for import looks similar quality to your link.

My confusion was based on that they asked for 'log' and I didn't know a) what log they meant (and they were closed) and b) the colorspace process in Resolve, having always used ACR.  I still am confused (and hopefully will stand corrected) about Cinelog with Resolve 17.  As the supplied transform from Cinelog for importing into Resolve (BMD Film -> Cinelog-C) is way off as compared to ACR.  My guess was that things have moved on since 2017, with BMD Film Gen4 being a different space than the import transfer that was written in 2017.  In any case, setting up Resolve as instructed on the Cinelog site isn't anywhere close to the ACR method. 

But yes, I'm definitely missing the point on what colourspaces we go through when importing DNGs directly into Resolve 17.  Personally, I edited straight from the DNGs in Resolve, and it was set to use the camera metadata - which resulted in a good picture.  But I was nervous as it seemed I was therefore already in Rec709 and I'm unsure of the consequences of going into Rec709 and back again to something like Arri Log.  So it made sense to me that we probably shouldn't go to Rec709 at all, and go straight from DNG to ARRI Log or whichever.  But I could see no way in Resolve to import the DNGs straight to BMD Film with the camera tone curve in order to output any of the possible log formats.

Incidentally, when I did eventually get to ask them about which 'log', they answered that I had to use .RD3 files and sent me a sheet of instructions.  But they also told me that ML is "only ever 8-bit up-ressed" which of course it isn't, nor would they accept DNxHR 444 - only ProRes 4444.  So I think I was a bit of a hassle for them from the start...

Anyway, many thanks for helping me out with this.  Really appreciated!