Ok - so thanks for the tips - and the solution I’ve now got RAW plates first going through a regular colorspace node - just changing primaries from sRGB to AlexaV3LogC
Next an add to eliminate the tiniest negatives…. A final OCIO colorspace node going from ARRI V3 LogC (EI800) wide gamut - to ACEScg And then a final reverse out of everything at the end - And this gives me the right results - zero negatives and a good looking pic. This tells me that the OCIO colorspace node doesn’t change primaries when going from ARRI to ACES / in fact expects the right ARRI primaries - and that this plate has been adjusted somewhere along the way. I’m guessing which primaries with the first conversion from sRGB to ARRI primaries ( which eliminates 99% of the negatives) - but it works and I can now work in ACES. Anyway - thanks for all the pointers N Neil Rögnvaldr Scholes Director | VFX Supervisor www.neilscholes.com <http://www.neilscholes.com/> +44 (0) 7977 456 197 > On 29 Oct 2016, at 19:25, Neil Scholes <n...@uvfilms.co.uk> wrote: > > Thanks for that I'll check it out. That might be a solution. > > Strange though as the whole point of the IDT is to bring the footage into > ACES without needing to offset etc. > > Yesterday I was also made aware that the plate may have peculiar primaries so > I've got a few ideas now to try out > > Thanks for the help > > N > > Sent from my iPhone > >> On 29 Oct 2016, at 17:21, Lucien Fostier <lucienfost...@gmail.com> wrote: >> >> Hey Neil, >> >> I had a similar problem than you on a show shot in Arri wide gamut. >> >> The first thing to notice is that Arri Wide gamut have very different >> primaries than Aces CG. >> >> In other words, some colors in Arri Wide gamut correspond to negative >> chromacities in Aces CG gamut. >> >> Besides this, the offset applied in the LogC can also introduce negative >> values. >> >> For working with your plate converted in Aces CG, you could intoduce an >> offset at ingestion time that would get reverted at output time. >> >> Cheers >> >> Lucien_______________________________________________ >> Nuke-users mailing list >> Nuke-users@support.thefoundry.co.uk, http://forums.thefoundry.co.uk/ >> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >> > > _______________________________________________ > Nuke-users mailing list > Nuke-users@support.thefoundry.co.uk, http://forums.thefoundry.co.uk/ > http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >
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