color accurate workflow in ACES for client approval

Question

general practice sort of thread...we're comping mostly CG renders, the client has specified final delivery in ACES-CG prores 422using new implementation of OCIO in after effects, we have our working space set to ACES CG, our footage interpreted as the same (16but float exr files from 3D)the viewing space is ACES/sRGBthe problem is, with the viewing curve, you can't actually get peak white (for text overlays etc)so we work in perceptual sRGB, deliver sRGB working quicktimes for client sign off, and they complain that the text isn't white, its greybesides trying to convince them that it's a short coming of the sRGB qts we're supplying, and when we send final ACES_CG 422 files to the grade, they will have peak white in them, how do we get the client to sign off the shots, bearing in mind they can't see the correct color and have to go on trust?!also concerning is that if you make a peak white solid in an ACES_CG -ACES/sRGB(viewing) comp, it calls it a light grey solid, in spite of the color values being 1,1,1looking forward to hearing people's opinions/feedback!

Shebbe · Answer

Adobe has plenty of feedback to adress a lot of short comings of it's OCIO implementation. Someone needs to just start doing the work but looks like it's not getting anywhere.

As to your 'problem'. "Peak white" doesn't really exist in a scene space. To reach sRGB display white you'd need a value of 16ish due to the tonemapping ACES applies. ACES tries to satisfy both a solid image pipeline for camera/cg work but also be a finishing tool which requires any data that actually shouldn't be altered to be an inverse of what the output tonemap is doing like sRGB graphics. While this can't be done perfectly it is usually close enough.

However since with OCIOv2 the view transform / display device is separated from color spaces (for good reason) we can't really do an inverse anymore. The way to do it would be via an OCIODisplay effect which can invert a display back to scene. This effect is missing in AE so you're out of luck unless you use the old OCIOv1 config which does have RRT+ODT "Output - sRGB" as a colorspace in the list.

In general i'm not a fan of the idea that ACES should provide a mechanism to make that work, you create issues with alpha when doing such inverses. Better to just have the full image pipe in ACES for the actual picture and any text/graphics/logos should be added after the fact to remove such constraints/issues.

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