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Issues using Keylight and Advanced spill suppressor with Alexa C-Log footage 32 bpc in After effects 2018 CC

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Alfonso Suárez
Issues using Keylight and Advanced spill suppressor with Alexa C-Log footage 32 bpc in After effects 2018 CC
on Apr 16, 2018 at 12:44:52 pm

Hi all,

I'm working in a project for a TV series doing some screen replacement with Alexa footage. When I have the comp ready, I deliver the file to do color grading. I've tried for the first time a new workflow, but Advanced spill suppressor is not working properly. Let me tell you the steps I'm following.

1. I turn on Color management, and I select HDTV (rec. 709) wich is the final colorspace. I also work in 32 bpc.
2. I import the Alexa footage, and I assign it the profile ARRI LogC3 Wide Color Gamut - EI800 (wich is the one used on set)
3. Do the comp.
4. Render a Quicktime DNxHR 444 10 bits and in the Color Management tab I also select as the output profile: ARRI LogC3 Wide Color Gamut -EI800.

When I try to do some keying and use the advanced spill supressor I find some artifacts. The main problems with keylight come with areas with heavy motion blur.
I suppose it is because I am getting colors up than 1,000 (as you can see in the attached pictures), because when I use Curves (for example) to reduce the exposure everything is working fine.
I wonder if there's a way to work this way. Or maybe I have to do the keying without assigning the profile ans using it as a matte for the footage, but then again I've got the spill problem.

This is the first time I use this workflow. I used to comp everything without worrying about color management, just working with the flat footage giving me by default in After effects when importing.

I'm trying to know if there's a better way of doing things. Any information will be really appreciated.
Thank you so much!!!






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Dave LaRonde
Re: Issues using Keylight and Advanced spill suppressor with Alexa C-Log footage 32 bpc in After effects 2018 CC
on Apr 16, 2018 at 3:20:03 pm

This sidesteps your issue, but since it's such a simple shape I would use Mocha in this instance. I don't see any spill that needs to be suppressed.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Alfonso Suárez
Re: Issues using Keylight and Advanced spill suppressor with Alexa C-Log footage 32 bpc in After effects 2018 CC
on Apr 16, 2018 at 4:28:43 pm

Thankyou Dave,

There's no problem with this particular shot, I only use it an example of how green the green gets (if this makes any sense) In fact, in the picture attached, the Advanced spill suppressor is only affecting the left corners of the TV.
My concern was more related to the workflow / way to work than this shot.


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Steve Bentley
Re: Issues using Keylight and Advanced spill suppressor with Alexa C-Log footage 32 bpc in After effects 2018 CC
on Apr 16, 2018 at 8:14:50 pm

Is the exposure control you are using (curves) perhaps reducing the greens available or converting antialiased greens to other greens - if you look at a histogram before and after a curves funciton you will find missing or "shifted" data.



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Alfonso Suárez
Re: Issues using Keylight and Advanced spill suppressor with Alexa C-Log footage 32 bpc in After effects 2018 CC
on Apr 17, 2018 at 8:16:08 am

I've found the problem when I'm not using any exposure control. If use it, the result is the following, which is what I wanted.




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Walter Soyka
Re: Issues using Keylight and Advanced spill suppressor with Alexa C-Log footage 32 bpc in After effects 2018 CC
on Apr 17, 2018 at 3:12:43 pm

[Alfonso Suárez] "1. I turn on Color management, and I select HDTV (rec. 709) wich is the final colorspace... 4. Render a Quicktime DNxHR 444 10 bits and in the Color Management tab I also select as the output profile: ARRI LogC3 Wide Color Gamut -EI800."

If you're inputting ARRI LogC3 Wide Color Gamut -EI800, and if you're outputting ARRI LogC3 Wide Color Gamut -EI800, why work in Rec. 709?


[Alfonso Suárez] "I suppose it is because I am getting colors up than 1,000 (as you can see in the attached pictures), because when I use Curves (for example) to reduce the exposure everything is working fine."

Very likely the case. You might consider reporting this as a bug:
https://www.adobe.com/products/wishform.html

Rather than using Curves and manually adjusting the green channel, you might consider using a Levels effect. Leave the defaults untouched, but set "Clip to Output White" to "On."

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Alfonso Suárez
Re: Issues using Keylight and Advanced spill suppressor with Alexa C-Log footage 32 bpc in After effects 2018 CC
on Apr 23, 2018 at 8:04:28 am

Hi Walter,
thank you for your reply!

[Walter Soyka] "If you're inputting ARRI LogC3 Wide Color Gamut -EI800, and if you're outputting ARRI LogC3 Wide Color Gamut -EI800, why work in Rec. 709? "

I work in Rec. 709 because is the color space of the delivery (TV series). Is that correct or am I doing something wrong?

[Walter Soyka] "Rather than using Curves and manually adjusting the green channel, you might consider using a Levels effect. Leave the defaults untouched, but set "Clip to Output White" to "On.""

I try using Levels and this is what I get. You can see the effect in the pictures before and after applying it. It gets rid of the green but then a blue halo appears. So I then assume I can't use After effects working with 32 bpc and log files? It's a pity!






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