Using a Rec 709 Lut trying to convert it to HDR delivery

[Glen Castinho]

Dear All

 

Hopefully make sense off this and wondered if this is ok i don't have the luxury on my current prj to do it any differently as the decision to got to Hdr was made later on .

i graded a show in a rec 709 using a rec 709 Lut ,now i need to deliver a HDR ver off this i wondered if this can be done using the colourspace space transform ofx and keeping the same  rec 709 lut while monitoring it on HDR monitor  i used resolve 16 to grade the show. any inputs ,various settings process ,  screen grabs etc  is highly appreciated.

Thank you 

[Orash Rahnema]

Hi Glen
did you place your lut at the end of the pipe or somewhere in the middle or at the begging?

 

[Glen Castinho]

Hello Orash 

Thank you for taking interest in this topic.

I placed the lut at the end off my node ,so its the very last node in my grade stack .

 

[Orash Rahnema]

Hi Glen!

I will assume you will have to grade hdr10 and not dolbyvision as would be a different

Since your lut is placed at the end I will try by replacing the lut with the color space transform ofx setting the output to rec709 and gamma 2.4

For the SDR version i will then chose the tonemapping option in the node for both luminance and saturation, in that way you should have the same result of the lut.

For the HDR version i will leave off the tonemapping option so the ofx will not softclip

I would honestly not tring to convert the gamma to pq or have a bigger colourspace as i you will probably have to redo a good chunk of your grade

living the gamma and the colourspace like the 709 but without clipping then you can go back to your nodes and do a very slight trim pass to push a bit more the hdr version and still both version should be similiar.

Let me know if this works for you

cheers,

Orash

 

 

[Orash Rahnema]

Edit: hdr will look super constrasty but you can do a "contrast" node right befor the ofx nod and fix the curve to have a similar feel, gamma 2.4 it's a lot more steep compare to pq

[Glen Castinho]

Hey Orash ,

Thank you very much ,i should have mention it is a dolby vision delivery requests

i appreciate the info shared