Hey @meleshkevich – The defaults in OpenDRT_params.dctl are approximately equivalent to the Rec.1886: 2.4 Power | Rec.709 preset. Unless you know what you are doing and want to experiment with the tonescale model, rgb weights, or other settings, I would strongly recommend that you do not use the _params version. OpenDRT is not a grading tool. The purpose is to provide a sensible and predictable set of defaults for rendering scene-referred images for different viewing conditions, which provides a good starting place for grading. Hope that helps. I am working on documentation that explains all this stuff… it just takes a lot of time 
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