Author Topic: Question regarding ML RAW > ACES  (Read 1064 times)

fibmedia

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Question regarding ML RAW > ACES
« on: March 22, 2018, 07:48:30 PM »
Hello all! I've had ML for a while now on my 5D3 but only recently started shooting RAW with it as I'm trying to learn more about color correction and grading. Still trying to wrap my head around everything.  I've been reading about ACES and am hoping to implement it into my workflow but I haven't been able to find all the information I'm looking for. From my understanding, ACES requires a known IDT, of which there sin't one for ML. I see that the MLV App has an option to convert to Slog3, Cineon, Alexa Log-C, etc. It seems to me that if I process my MLVs with MLV App, convert to one of these known profiles and then use the corresponding IDT, I should be able to uses ACES with ML RAW. Is my thinking correct? Additionally, do I need to export to ProRes 444 for the conversion to stick? or do CDNG files embed that color transformation? I apologize for my ignorance and any help is much appreciated.

Andy600

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Re: Question regarding ML RAW > ACES
« Reply #1 on: March 23, 2018, 11:03:29 AM »
The ACES container format file (EXR) require a camera-specific IDT because the colorspace and white balance are already defined as (or should be) Linear ACES AP0 primaries. DNGs do not have a defined colorspace as such but the color matrix/matrices and white balance multipliers describe a transform to XYZ space and from there the ACES app can put the data into ACES AP0 colorspace. Problems arise when the white balance matrices are not correct/accurate or the implementation of color management/ACES in the app is not handled correctly.

Re: MLV App. Assuming the colorspace transforms are correct in the app (haven't tested so I'm not sure if it is), the corresponding IDT for your chosen output colorspace settings should work in other apps (Resolve, Nuke, Fusion etc). If you are creating intermediate log files you should aim to retain as much color information as possible so choose ProRes XQ or 444.

You should note that all PC based MLV apps are typically built with FFMPeg/Libraw libraries so the codecs are not official Apple ProRes and are limited to 10bit. This may be an issue if you create content for TV broadcast.

If you really want to use ACES I would suggest converting your MLVs to DNGs for use directly in DaVinci Resolve. However, initial color accuracy will depend very much on the MLV2dng conversion and how the converter implements white balancing, color matrices etc because they are not all the same. Keep your MLVs safe until your are satisfied with the raw2dng conversion.
Colorist working with Davinci Resolve, Baselight, Nuke, After Effects & Premier Pro. Occasional Sunday afternoon DOP. Developer of Cinelog-C Colorspace Management and LUTs - www.cinelogdcp.com

Danne

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Re: Question regarding ML RAW > ACES
« Reply #2 on: March 23, 2018, 12:20:56 PM »
Hi Andy600. If you could check color accuracy in Mlv App and give your valuable opinion it would be nice imo.

Ilia3101

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Re: Question regarding ML RAW > ACES
« Reply #3 on: March 26, 2018, 10:36:10 AM »
That would be fun and interesting.
@Andy600 contact me if you have any questions if you do this.

For testing:
Use the "WhiteBalance" branch (soon to be merged) which should have correct sRGB/rec709 output. White balance in that is however done in XYZ, not yet any kind of LMS space. Me bouncyball or MASC can provide you a build for whatever OS your using.

Also the "log profiles" are nothing more than curves (no colour stuff).

Current mainline MLV app has absolutely no "colour accuracy", so colour testing should only be done in WhiteBalance branch or wait for merge.
5D2

70MM13

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Re: Question regarding ML RAW > ACES
« Reply #4 on: March 28, 2018, 12:09:20 AM »
I'm really impressed with what you guys are creating here.

I hope you merge that branch soon, I can't wait to use it!

Keep it up, it would be incredible to one day be able to do colour accurate grading right from the mlv!

Highlight control too, please...

Thanks for your efforts!

Ilia3101

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Re: Question regarding ML RAW > ACES
« Reply #5 on: March 28, 2018, 12:13:47 AM »
Highlight/shadow control coming in next release which might even be really soon. Even before WhiteBalance branch is merged.
5D2