We are working on a couple HDR animated features. We have implemented a ACES pipeline which allows the comp artists to work using a sRGB ouput transform in Nuke. The shots are then rendered as ACEScg and brought into Resolve. In Resolve we color correct in HDR and then do a SDR trim pass.
The current issue is that the sRGB output transform doesn’t look anything like the Dolby Vision SDR output. All our client reviews are based on the sRGB output transform, which are not going to look like the final output.
My thoughts to solve this is for the artist to use a [rec709 - ST.2084(PQ) - 100nits] display transform so they can better see how the final is going to look. We would also bake this transform in the the review MOV files so the client can better understand how things will look.
Does anyone know if this transform exist, or if it is even possible to create a output transform like list?
Would a custom transform like this be hard to create?
I understand that there is Max/Min analyzing that is done by Dolby Vision to hit certain target nit levels, but there must be a way to use the PQ curve in the ACES transform.
I’ll take a stab at this since I was looking at implementing something close but not quite in order to make our (current) SDR output closer to our (target) 1000 nits HDR output.
So, as far as I know, there is no default transform to target PQ 100 nits evenless so with rec.709 colorimetry. Moreover, unless you plan to make your own viewer tool, the PQ curve is incredibly alien to SDR monitors. It is possible to take a PQ 1000 nits image and display it reasonably on a SDR through a custom shader — I made one so I should know — but there’s a lot of voodoo magic involved based on what you think looks good.
On the flip side, there is the HLG curve which is very compatible with standard monitors and it would only take a very small modification to output a Rec.709 HLG image so it would properly display on a standard monitor and this is exactly what I’m thinking of doing right now. If you’re using CTL, you only have to copy the Rec.2020 HLG output transform to a new file and change a few lines of code. It should also be fairly easy to do in Nuke from what I read on this forum although I have no experience with it. For Resolve, you will probably have to generate a LUT. As for OpenColorIO, I have no idea at all.
How about using an HDR10 display transform in Nuke instead? I’m not sure how well HDR works in the UI viewer, but at least it would work on the SDI monitor output.