Blackmagic Forum

When converting HDR video (Rec. 2100 PQ) to Rec. 709 using a node-based DaVinci Wide Gamut (DWG) Intermediate workflow, the output appears slightly different compared to using the Auto Color Management environment in the Project Settings. This difference is more noticeable in footage with orange and yellow tones.

However, if we convert directly from HDR (Rec. 2100 PQ) to Rec. 709 using a node-based workflow but without DWG Intermediate, the result matches what Auto Color Management produces.

I've attached a video for reference. Could someone please let me know if I'm doing something wrong or explain the reason behind this behavior? Thank you

Video was not uploaded here, please go through the link below for Ref.

https://drive.google.com/file/d/1OzJBnj ... drive_link

When you say Auto Color Management do you mean the automatic HDR setting? This setting does not use DWG/I as the working space but rather Rec.2020/Intermediate. The DaVinci DRT (that which tone maps scene to display referred and vice versa) behaves differently depending on what the color space is it is applied to hence you'll see differences if they do not fully match. Try the non automatic HDR DWG/I preset instead and see if it matches.

Since it's your first post you can't share links yet so can't exactly see what you meant. You can try posting the link with some extra spaces in between so it's flat text.

shebbe wrote:Since it's your first post you can't share links yet so can't exactly see what you meant. You can try posting the link with some extra spaces in between so it's flat text.

I've made a video, here is the link: https://drive.google.com/file/d/1OzJBnj ... sp=sharing

I see so you were also comparing both methods through nodes. The principle still stands. The DaVinci DRT operates directly on the incoming input color space rather than it’s own rendering space which is why the appearance will change depending on what color space you convert from scene to display. DWG’s primaries are set up to give generally pleasing and usable results and would be recommended as the working space when using DaVinci as the tone mapper if you plan to grade in log and use a variety of input data from different cameras. But there is no ground truth there only preference and practical implications.

I think what's important to know is that if you plan to grade at all, it would be best to use a log working space. In the case of Automatic Management you could pick Auto HDR instead. As confusing as it sounds you can use this for SDR. It just means that the working color space is Rec.2020/Intermediate. It matches your input PQ clips' primaries but the transfer function is log rather than PQ making it suitable for grading operations.

If you prefer to grade after display conversion then automatic SDR can be a choice because there the working space is the same as the output space. It's already converted to SDR 100nits before any grading operation happens.