I have been using Aces on my last couple of projects, all going relatively smoothly so far.
My issue arises when converting artwork to Aces, which needs to be premultiplied.
In Nuke Studio, I will always get ugly edges when converting to aces and then masking by the alpha on the timeline. I get the same issue when trying to convert and render via nuke. The problem happens because the colour values (for white) are going from 1 (in normal rec project) to ~16 for Aces. However the alpha is not changing, and so semi-transparent areas are reacting differently when pre-multiplied
eg
Aces - Colour = 16 * alpha .5 = final picture value 8
rec - Colour = 1 * alpha .5 = final picture value .5
See the attached screenshot to see what I am talking about. Note that this screen shot has a viewing Lut of ‘standard’ rec709, and so the bottom legal line looks correct, and how I want my Aces artwork to look. I can not do it this way though as the ACEs_rec709 lut needs to be applied for the footage to look correct.
In the past I have had my masters timeline change back to rec709, and so all legals etc work as expected, but I don’t want to be forced to work this way and would rather keep AcesCg the whole way through, to avoid changing viewing Luts/export types etc
I’d also love a solution to this. I encountered it inside Resolve (ACES workflow) when receiving text animation to comp over live action as an exr file.
Titles and logos should be applied after the ODT. Then you don’t run into any problems.
This you can easily do in a system like Autodesk flame, because you can add a gap track in the timeline that applies the ODT and add your logos and titles on top of that.
I am not sure how to do this in Resolve or NukeStudio, but what you want is more or less this:
ACES footage, apply RRT&ODT (Rec.709), comp logos on top and set the IDT again to Rec.709 to get back into ACES. Be careful as this is a lossy conversion. We created a nuke gizmo to add normal logos onto an ACEScg comp like this…being aware that this should be the last step before writing out a comp.
Adding a white Photoshop title/logo in ACES with Output.Rec709 as the IDT is as you are adding a self illuminating object into the scene. Thats why it doesn’t make sense and it doesn’t work well.
Thanks Daniel, We ended up doing it downstream like you say, would be nice to have a way to get it right inside of ACES. Thanks for the reminder about values in the scene referred space. Currently i’ve been experimenting with building a DIY ACES pipeline in resolve using the ACES Transform OFX , which allows one to work after the ODT.
Thanks Daniel, that is the method which seems to give the best results. I ran in to some instances where this method wasn’t possible, but rethinking back now it may have just been set up incorrectly. Mainly it was graphics which dissolved with picture. When I am back in the office I will re-try and report back.
