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Create a Rec 709 conversion lut for Rec 2020 footage

Forum|Forum|6 years ago
March 21, 2019
4 replies
32019 views

After finishing Grading my Rec 2020 footage, I would like to create a LUT so that it can also be viewed in rec 709, SDR. Right now when I export the footage, I only get my graded HDR footage.

it looks bad on SDR monitors, I would like to have a 709 conversion lut created so that it can viewed on SDR monitors.

I'm trying to do this so when I upload footage to youtube, I can attach the 709 lut so that it can grade the conversion properly.

Here is what is happening with regular HDR footage:

Composite Arf Hawk RC Turbine Jet - 4K HDR - YouTube looks good on HDR monitors but bad on SDR

So I have to re-encode it using rec 709 color profile and reupload as a 2nd file:

Composite Arf Bae Hawk Carf RC Jet - 4K SDR - YouTube

obviously not very practical, so what can be done here. Youtube says it offers a way to have more control over SDR conversion but needs a lut to do this with. the instructions are for divinchi resolve.

Correct answer francis-crossman10980533

We have an effect called SDR Conform which is available in Premiere Pro and Media Encoder which is designed for tonemapping HDR footage to a Rec709 color space. You could apply it at the time of export by drilling into the export settings and finding SDR Conform in the Effects. You can also use it in Media encoder in the same way. Another way to approach it would be to duplicate your sequence and add an Adjustment layer. I like this method, because you can more easily spot check through your program and make sure things are looking good in a Rec709 world. There are some setting that you can adjust in the SDR Conform effect (Brightness, Contrast, Soft Knee). Soft knee is how much you roll off the highlights. This effects is better than a LUT because you can tweak it to best suite your specific content. I hope this helps.

R Neil Haugen

Legend

One thing to be aware of is a LUT is "the dumbest math out there" according to colorists. Yes, you can make one for this purpose, but as Francis notes above it's better applied on the timeline where you can 'trim' the clip to fit the LUT. Or you can have clipped/crushed or over/under saturated values.

A tonemapping is a far more complex operation and in many ways preferable for transform uses. Such as their SDR Conform, which both transforms color space and dynamic range from one standard space to the other. Not perfect but quite usable.

Neil

Everyone's mileage always varies ...

chrisw44157881

Inspiring

@R Neil Haugen ill have to double check if sdr conform changes the color gamut as well? if it does not, maybe a combination of gamut conversion lut and luma conversion.(brightness, softness, knee tonemapping.

I do all my funky stuff in resolve, so haven't played around with sdr conform like I should.

R Neil Haugen

Legend

SDR Conform by design must handle both gamut/space and dynamic range conversion. That's the reason it exists.

Neil

Everyone's mileage always varies ...

V

victorwuff

Participant

Thanks for the information.

But beside adapting dynamic range BT2020 to Rec 709 also needs a colorshift. colorspace of BT2020 is not only wider but has also shifted colors. are there any plugins or adobe effects to shift Colors between this colorspaces?

B

Birgit-Michelle5CB8

Participant

There is a lut that corrects the color shift: cc-lut.hotglue.me

B

bernhard5CB8

Participating Frequently

https://cc-lut.hotglue.me/

SimrunTechAuthor

Known Participant

Yes I saw the SDR conform however, what happens to the output? My understanding that if I enable this I will get SDR output and loose HDR? Or are you saying it will output 2 graded files 1 for SDR and 1 for HDR?

OR.. will I get an HDR output along with a LUT that converts the HDR to SDR? This would be the ideal, I could then package both of these for youtube.

Sorry if I seem repetative, but I haven't found anyway to upload HDR footage to youtube that allows me to control the SDR conversion youtube does.

E

excited_Genie16B8

Legend

You need two exports.

francis-crossman10980533Correct answer

Adobe Employee

We have an effect called SDR Conform which is available in Premiere Pro and Media Encoder which is designed for tonemapping HDR footage to a Rec709 color space. You could apply it at the time of export by drilling into the export settings and finding SDR Conform in the Effects. You can also use it in Media encoder in the same way. Another way to approach it would be to duplicate your sequence and add an Adjustment layer. I like this method, because you can more easily spot check through your program and make sure things are looking good in a Rec709 world. There are some setting that you can adjust in the SDR Conform effect (Brightness, Contrast, Soft Knee). Soft knee is how much you roll off the highlights. This effects is better than a LUT because you can tweak it to best suite your specific content. I hope this helps.