As far as I can tell this should be “Improved AcesOtOperator unmapping in case alpha is 1.0 - Fixes issue that CoronaTonemapControl did not negate the effects of the AcesOT operator.” in https://forum.corona-renderer.com/ Chaos Corona 10 for 3ds Max - Daily Builds Changelog #msg206878 , so is in the 10 daily builds since then.