Exporting in Premiere: BT.709 or BT.2020 Transfer Characteristics - Does it matter?

Question

Hello, any help appreciated with this weird question;

I have video file 3840x2160, it is in SDR (no HDR). I wanted to possibly apply an effect to it but also wanted to lower the bit-rate on it some. My exports from Premiere Pro (2021 & 2023) using H.265 (I've tried various settings - Rec2020 on\off, HDR on\off) never get me to match what the original file states under "Transfer Characteristics" using Mediainfo.

Here is where they both match:

ColorSpace: YUV

Format: Main 10 @L541_2.1 @2651121

Chroma Subsampling: 4:2:0 (Type 2)

Bit Depth: 10 Bits

Color Range: Limited

Color Primaries: BT.2020

Matrix Coefficient: BT.2020 non constant

This one however does not match: Transfer Characteristics

Original is BT.2020 (10bit) and exported is BT.709

The video looks great, just as good as the original (on my monitor anyway). I believe when I checked off "HDR Metadata" it gave me "PQ" there and that one the colors looked washed out.

The funny thing is I believe I have done this correctly before. I have the same type of file from about a year ago that I also checked and somehow\some way (I'm pretty sure using Premiere?) I was able to get that to state "BT.2020" for that area matching the original.

R Neil Haugen · Accepted Answer

Well this is new to me... According to the Wiki for BT.2020 (ITU-R recommendation BT.2020) allows the use of SDR & BT.2020

"various aspects of ultra-high-definition television (UHDTV) with standard dynamic range (SDR) and wide color gamut (WCG)"

And I found a few other sources that claim it possible & apparently occurs though rarely. So if that is the case I then go back to my original question on why Premiere will not allow me to export that way; not allowing export of the Transfer Characteristics of BT.2020 (10bit) and I suppose more importantly, if I cannot does that setting even matter in the case of SDR material?

You'd have to get a staffer for that. But at a guess ... it's because that is such a rare case. I don't know of a TV out there that would properly support WCG ... wide color gamut ... in SDR/Rec.709 DR and setting.

So ... how would anyone view it?

And ... why would you want to export it too, as there's nothing that can use it in any practical way. It's more of a 'theoretical' thing is my understanding.

R Neil Haugen · Answer

You say you have a video file that is SDR ... which is Rec.709/Bt.1886.

Rec.2020 is HDR.

So I'm wondering what it is you're trying to match, as to me, your listed data and results don't make sense.

Is the original clip Rec.2020? or Rec.709? Which?

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