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LOG color workflow with effects in PPRO

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Weston Jones
LOG color workflow with effects in PPRO
on Sep 13, 2017 at 3:59:43 am

Hello,

I'm working with ARRI LOG footage with intention sending the footage to a colorist to apply color adjustments. I'm not finishing in Premiere. I've been working with an input LUT applied as a master clip effect to each clip to give me rough idea of what the footage will look like. Ive gone about cutting and adding various effects and transitions and some compositing, both in Premiere and AE.

I'm now preparing the footage for the colorist, and finishing VFX work. I want to deliver a flattened LOG Quicktime. To get there I have disabled the input LUTs that were applied as master clips effects, and applied the same input LUT to an adjustment layer over all the footage, as a top layer in my sequence. I'm doing this so I can make my entire sequence, footage and the effects applied, translated into the flat LOG color.

The contrast and color curves added by the LUT on the adjustment layer is now messing with the effects. Which I anticipated, but I'm finding it pretty hard to correct. In particular cross dissolves, or any layering of color solids with opacity changes, especially if blending modes are set to something other than "normal". Screen or Add modes behave very differently with a LUT over them. Its not always easy to fix it either. Its rarely just an issue of increasing the opacity by 20% or something. And it seems that sometimes in fixing it, reducing the contrast etc, it I also introducing artifacts, like banding and noise, into the image.

The same holds true in After Effects, but it is a bit easier to fix there. My experience is AE compositing algorithms are usually much better the PPRO. But its still a pain there too. I've tried adding input LUTs that do REC709 to LOG to the graphics and solids, but it doesn't really work. Maybe i'm not using the right input LUTS though? The LUTS I'm using on the camera footage is the "Alexa Default LOG to REC 709" and the "Alexa V3 K1S1 LOG to VIDEO DCIP3 EE"

Is there a strategy you would recommend for how to go about translating the effects work done in premiere (and AE for that matter) to LOG? I'm really hoping its not true that if you are going to apply any effects or dissolves etc to LOG footage in Premiere, you have to finish it in premiere. But I also cant imagine how else the master clips would work.

An example to reiterate the problem: Take some LOG footage, apply a input lut to it. Place a white color matte on top of the footage, make the white matte in "Add" mode, and create a ramp from 0-100 opacity. View result. Now disable the input LUT on the clip, and place it on an adjustment layer above both the clip and the white color matte. It will look different. How do you fix it so that a colorist down the line can apply a LUT to the clip and it looks as it should?

Another issue, when rendering the preview within premiere with the LUT applied on the adjustment layer, it looks different than when I export it. Same settings for preview/sequence setting and export (ProRes 4444)

Any help is greatly appreciated, thank you!


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Chris Wright
Re: LOG color workflow with effects in PPRO
on Sep 13, 2017 at 6:08:33 am

1. huh? just put the white matte above the adjustment layer. you can then use the adjustment layer for your lut on top of footage. or, depending on how many clips, nest the footage and its adjustment layer before adding composites or effects.

2. previewing and exporting sometimes run in different gamuts. premiere's opengl program monitor runs at srgb 2.2 gamma, so you have to calibrate your monitor to that as well. vlc matches that if you set video output to opengl and change gfx control panel settings to 0-255 with enhancements turned off. quicktime runs at 16-235 gamma 1.8 and
a lot of monitors default to adobe rgb or P3. you can either use a transform lut or re-calibrate your monitor to srgb(rec 709 gamma 2.2).


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Weston Jones
Re: LOG color workflow with effects in PPRO
on Sep 13, 2017 at 3:57:26 pm

Thanks Chris.

The stuff in #2 about gamma an export makes sense.

But regarding the LUT's, I am not finishing the movie in Premiere. It will be going to a colorist who is likely using Davinci Resolve. So I'm planning to have the movie flattened before sending to color. I can't put the effects above the color in a layer order this way. Maybe its possible to send layers to the colorist, but sending PPRO cross dissolves to Resolves sounds dangerous. And I would prefer the colorist to be able to adjust color for everything, including the dissolves and effects. Does that make sense?


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Chris Wright
Re: LOG color workflow with effects in PPRO
on Sep 14, 2017 at 2:38:04 am
Last Edited By Chris Wright on Sep 14, 2017 at 2:43:48 am

anything not supported in XML you need to duplicate sequence, turn off extras before exporting. cross dissolves should still work though. many effects won't, sorry.

true vfx shouldn't be graded until after they are composited because a good composite requires both ungraded vfx AND ungraded footage so they will match seemlessly in post. Just try to heavily grade an explosion and then later add the vfx elements, hehe, nope! they are seemlessly composited with a viewing lut, THEN graded as a single image.


finally, edit them later as a flattened VFX shot import as XML from nuke with 12 frame handles, or manually right click, replace with clip from bin.


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Weston Jones
Re: LOG color workflow with effects in PPRO
on Sep 14, 2017 at 4:01:10 am

Thanks Chris.

So what you're suggesting is anything that isn't supported with XML (or EDL right?), then I would want to make sure the composite image is in the same color format, LOG in my case. The method for doing this is placing an adjustment layer on top of everything, footage + composite VFX elements, and creating the image. This is the same thing as working with a "viewing LUT", as you mention, right? This is the method I've been following in both AE and PPRO: https://www.rocketstock.com/blog/tips-for-log-color-space-compositing/. Your explosion example is in there.

Makes sense to me, but this is also where my problem is. I'm finding it really hard to create the effects with the heavy contrast caused by the viewing LUT (adjustment layer) over the effects work. Blending modes, opacity, fades, gradients, are much harsher. Effects that looked great before, I'm finding nearly impossible to recreate.

Am I over thinking this or something?

I'm planning to speak with a colorist soon, which I wish I would have done much earlier, but I haven't hired on yet.


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Chris Wright
Re: LOG color workflow with effects in PPRO
on Sep 14, 2017 at 6:43:12 am

woah, uh, that post is wayyy off, its saying to convert cgi from rec 709 linear to log to composite, haha! yea, good luck compositing something created in rec 709 and then faux expanding to wide gamut log. the correct workflow is render cgi 16 bit linear float AP0 2065 EXR master plates in ACEScg. if you render cgi in rec. 709, you're clipping all your gamut colors before you even composite! you use rec 709 as viewer RRT luts, not compositing colorspace. See Step #3 VFX Magic, Step #4 Importing & Refining The Grade below.

if your colorist doesn't know what ACES is, forward them these links and read a few times.
https://mixinglight.com/color-tutorial/getting-to-know-aces-part-3/
http://www.oscars.org/science-technology/aces/aces-documentation


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Weston Jones
Re: LOG color workflow with effects in PPRO
on Sep 14, 2017 at 5:42:16 pm

Thanks Chris. I've spent a few dizzying hours reading about ACES. This video shows the ACES workflow using OCIO plugin for After Effects:





That workflow is correct right? Once the color management is setup with the plugin, and the proper input and outpost settings are used (either on adjustment layers on a clip by clip basis), then one can work within AE as they normally would. Meaning all LOG + Rec709 elements +blended solids and effect, etc, can be composited to the eye in a desired LUT, and then exported in a flat color look for later grading.

My only question is how do I the same within Premiere? I cant find any documentation on OCIO implementation with Premiere. If thats true, then is any visual effects work with LOG footage in premier not able to be combined and output in LOG?

Thank you.


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Weston Jones
Re: LOG color workflow with effects in PPRO
on Sep 15, 2017 at 2:04:05 am

This video was super helpful and demystified this whole process: https://www.provideocoalition.com/after-effects-and-alexa-part-2/

The bottom comment also address mixing colorspaces in the composite.

Still unclear how this works in Premiere, but I guess I will do any FX work over in After Effects then.


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Chris Wright
Re: LOG color workflow with effects in PPRO
on Sep 15, 2017 at 4:32:00 am
Last Edited By Chris Wright on Sep 15, 2017 at 4:37:36 am

that is a very useless video. *sigh*.
--------------------------
All cgi is rendered linear. Rec. 709 is not linear. if you "burn" in a rec. 709 lut, you won't be able to composite correctly. The arri also uses whats called a wide gamut colorspace, much, much larger than rec 709. Using a "nuking" lut like this is for doing low end things like viewer luts, creating bluray or youtube, not vfx or cinema. it effectively cuts after effect's colorspace down to rec. 709 while simultaneously burning in heavy contrast.

The general how-to is separated in three steps:
1. Converting logC data to linear data
2. Data preview using a Rec709-viewing-LUT", composite in linear
3. convert linear back to logC after compositing

you want something akin to LogCToLin, work on footage with "viewer" LUT, LinToLogC export. you can go 3 ways
1. opencolorio ACES, the easiest and most platform compatible(recommended)
2. no working color space, everything converted with apply lut effect or color profile converter. cube,cdl
3. full color management, enabled in projecting working space as arri wide color gamut icm's, icc's

if using color management, you can go to view- simulate working space rec. 709 for your viewer lut. linearize workflow. if your working space is smaller than wide gamut footage, the adobe color engine will clip the color primaries before even compositing.

if not using color management, you can put the viewer lut on the very top as an adjustment layer as it won't affect the final composite(AE renders bottom to top) note: disable it prior to rendering or use guide layer. Finally, export as EXR half float AP0 2065. example: http://generalspecialist.com/vfx-behind-akta-manniskor/


some other guides for the colorist:

alexa color processing whitepaper
http://samyscinemaworks.com/wp-content/downloads/ALEXA-Color-Processing-Whi...

arri downloadable conversion tools
http://www.arri.com/support/downloads/searchable_downloads/

dailies creation resolve workflow
http://www.arri.com/?eID=registration&file_uid=15721

looks editorial meteadata guide
http://www.arri.com/?eID=registration&file_uid=15721

----------------
final note:
Premiere doesn't have color management control. only lumetri with lut input. It's engine is rec. 709 only unless you use jpeg2000 rec2020.


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Chris Wright
Re: LOG color workflow with effects in PPRO
on Sep 16, 2017 at 12:53:40 am

keep in mind, premiere doesn't support arri wide gamut directly. once you import your graded footage from resolve back into premiere, it will lose any work you did if you graded higher than rec. 709 in resolve. i.e. wide gamut, rec. 2020, p3, etc. All your work will be color clipped and show artifacts. So, if grading in a large colorspace, finish editing in resolve, there's no going back.


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Weston Jones
Re: LOG color workflow with effects in PPRO
on Sep 19, 2017 at 12:04:47 am

Thanks so much Chris, this is really great info. The way I've been working is with the 2nd option you describe, as is also outlined in the http://generalspecialist.com/ link.

The only difference is I haven't been setting and input LUT on RBG sources to convert from Video to LogC, but instead have been turning down contrast and saturation as necessary so the composite works under the top layer adjustment layer. Is this destructive to my RBG footage? Isn't an input LUT on the layer from Video2LogC effectively doing the same color work on the RBG footage, just as a quicker way to get there?

Blending modes behave differently with the input LUT on. Screen no loner makes black transparent (because black is more grey from the LUT). Though the "lighten" mode seems to work like screen using this method. Is that normal?

Thank you.


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Chris Wright
Re: LOG color workflow with effects in PPRO
on Sep 21, 2017 at 1:56:16 am

nothing is destructive if its a guide layer. you don't have to use luts for things, they are simply luma and chroma changes you can do by hand. you can make your own technical luts that work even better than manufacturer's luts with better detail and skin tone line. luts aren't smart, they don't know what exposure and iso you use. they only care about white balance. and yes, linear light affect blending modes differently. fxguide has many good reads on that.


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