Acescg super whites

Hi GUys,

How do you deal when we have got super whites in ACES? I’ve been keying some content in Aces and sometimes the whites of the background are so strong that it cut through the Foreground. Any tip on how to deal with this? I am converting my image to REC709 and comping in REC709, but I would love to work fully ACES throughout the comp.

Thank u Guys,

You can try clamping the BG whites through the FG alpha.

Lately I’ve been doing so much of my keying work in acesCC and going back to acesCG after just to avoid those kinds of situations.

I can’t say it will work for you and your workflow but I do believe it’s worth a try.


Yeah I’m with @cnoellert

Those super white values you get sometimes in sceneLinear can easily burn through a matte.

A conversion to log will help you.

If you are going to convert try and use a colour space that will keep your HDR.

There is a danger that if you go to rec.709 that you will loose some information.

I regularly bounce back to Arri LogC since most of my source material started life as logC but any log can help you.


I’ve been running into the same issue this week and do exactly what @cnoellert has mentioned. Keep everything in ACES but go log to comp the two plates.

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Comp in log? is that technically correct?


It depends. ACES is just an umbrella of formats. It contains archival, linear working, and logarithmic work in color spaces. The best part of it is that you can bounce back-and-forth between linear and log depending on the task you need.

Don’t forget that some composing tasks should definitely not be done in linear. And some tasks are better done in log. Bouncing back-and-forth ACEScg and ACEScc it ACEScct is fine, expected and encouraged.

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I meant talking specifically about the comp op (comp node or action), not comp as a general procedure. As I think, comping two images in log gamma is not the best thing.

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well, you can comp it in log, it may solve the issue, but your operations will not be totally accurate. blend modes, operation and some fx inside action will not behave propertly. but maybe you dont need that precision in you comp. that’s up to you.
I usually switch to log just for degrain, key, color correction, etc… keeping the comp in linear.
the key in here, specially if you are tranforming from rec709 to aces cg, is what is happening in that transformation.

I tried that Milanesa. It was the first thing I thought, but when I clamp my shot the highlights doesnt look good and I lose all the AcesCG range when it goes to grading.

Yeah Saul… actually I haven’t noticed any loss of data once I go from Aces > Rec709 (Keying) > acesCg back to send to grade. Looking at the transformation I am doing, I might have lose any data.

What I meant was to clamp or softclip the whites using the FG alpha… so the key matte. Specially if you want to keep the comp operation in linear. But yes, depends on the type of shot, it may make more sense to do a Log comp.

Also, are you doing a Rec to ACEScg transform? Because if you are doing a Rec to ACEScg via an Inverted View Transform, what was once like 0.8 or 0.9 in Rec will become much much much higher in ACEScg, so, you should try an Rec to ACEScg via an Input Transform, and just deal with the color shift and grade to match.

Or log.