Create a Rec 709 conversion lut for Rec 2020 footage

[SimrunTech]

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.

[francis-crossman · Accepted solution]

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.

[Kevin-Monahan]

Thanks for the reply, Francis.

Kevin

[SimrunTech]

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.

[excited_Genie16B8]

You need two exports.

[victorwuff]

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?

[Birgit-Michelle5CB8]

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

[bernhard5CB8]

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

[victorwuff]

right: this lut helps a lot.

[chrisw44157881]

.

[bernhard5CB8]

@chrisw44157881 Hi, I did a quick comparison of your LUT with the one from pointecc and it is not similar, not even close! pointecc does an accurate translation of colors from BT.2020 to Rec.709, producing results comparable to color space transform in Davinci. The LUT you posted obviously shoots past the reds and is definiteley not a conversion from BT.2020 to Rec.709.

[chrisw44157881]

@bernhard5CB8 

yes, I made a mistake that the gamut wasn't also converted.

also, I don't personally agree with paying for a technical lut. a creative lut sure, but technical luts should belong to all the smart engineering people at ACEs who give away their knowledge for free.

here's a free online lut creator that you can create entirely in your web browser. I found that setting HLG  .2100 input and Rec 709 output is close with a higher gamma i think 2.2 instead of 2.4

http://cameramanben.github.io/LUTCalc/LUTCalc/index.html

[luka3rd]

Couldn't agree more on technical LUT standpoint, as realistically - once made - it's final. No modification will ever be needed and number of combinations are definitive.

My issue is that I can't find a way to properly monitor my Nikon's HLG footage on external monitor... It looks wash out, but any of the LUTs I have are for N-Log, which is far more desaturateted to begin with... I'd like to comprehend that LUT tool and make one, it looks simple to me - as I don't have almost any knowledge on it, if you understand what I mean.

It should ideally only convert BT2100 to BT 709, but I expect to stumble on many things I won't understand...

[R Neil Haugen]

Does Premiere's tonemapping work on the Nikon media?

As if it does, as someone who works for/with/teaches pro colorists  ... aan algorithm transform is nearly always preferred for normalization or transforms over LUTs due to the nature of the two tools.

LUTs are "dumb", they're just a chart of orders to change X RGB triplicate to Y. And they will crush or clip any data they weren't built on.

Algorithms are high end mathematical formulas and will not clip or crush.

Yes, I've made a ton of specialized LUTs over the years in Pr, Resolve, SpeedGrade, LutBuddy, and LutCalc. For about anything you can think of.

But I rarely use any today in either Pr or Resolve as the tonemapping renders them essentially obsolete.

[luka3rd]

As far as I can tell - it does.

Issue is that my camera shows relatively saturated colours, but my external monitor shows washed out colours, I guess it doesn't read BT.2100 properly... but it reads LUTs, so - somehow it looks to me that it needs correction from one to another, I'm not sure how to reproduce that behaviour in Premiere?

[R Neil Haugen]

What is your OS? What is the monitor? Have you done any calibration or settings changes in the monitor?

Do you have Display color management on in Premiere, and what viewing gamma do you have set?

[luka3rd]

I think we might have a misunderstanding here, I reffer to it as "external monitor", it is a "field monitor", on camera, Viltrox DC-X2. I am very sorry if I wasn't too clear.

Otherwise, my PC is on Windows 11 and it's calibrated, about a year ago last time, some Samsung, 27", old guy, but still holds 🙂 and Premiere is set to Web gama (2.2).

But I'm not having problems with desktop 😞

[R Neil Haugen]

Oh, are you wanting to create a LUT to fix the field monitor while shooting?

[luka3rd]

Yes! Exactly that 🙂 I knew I'll fail to even define the problem corectly...

So, any hints, please?

[R Neil Haugen]

That's ... a joy, innit?    😉

I just read through the short little pdf file that is the "manual" for this.

So, you can either set the contrast/saturation controls, or load a 3D LUT into that monitor. 

If you're only doing format out of the camera, if you can simply jigger the monitor controls would be probably workable. One doesn't expect total "accuracy" from a field monitor, just enough so you can see composition, check false color/zebras, typically.

If you do some Rec.709 and some say HLG from the camera, you'll probably have to go the 3D LUT process. If you can find someone on Reddit or a Slack or somewhere who's already created one, that's slick.

If not, it's trial and error. Make a transform LUT in say LutCalc that includes the needed color space transform and the tonal changes you want to try. Load it into the monitor, and see what happens.

Make changes, rinse & repeat. I've heard quite a few DPs and especially those talking about time spent as an assistant DP or camera operator, where they spent the odd week doing this getting ready for a shoot ... over and over.

[luka3rd]

Yes, that's it. I am doing exactly that... I found that I like either SDR for lesser work or HLG for more control or creativity, N-Log is not my cup of tea. I found that HLG gives me pleasing contrast and colours with almost no or minimal intervention in post.

Thtat's it than, that's exactly what I'll do. Seems achievable and logical.

I'll dive into it ASAP 🙂

Thank you for many wise words and all the sharing and effort! Very generous!

[R Neil Haugen]

Happy to help.

Btw, ALL HDR formats are log-encoded. So that HLG is actually a log format.  😉

[luka3rd]

Oh, thanks... I'll have that in mind.

[R Neil Haugen]

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

[chrisw44157881]

@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.