Color Gamut in VLOG-Recording

[Joachim Claus]

I have a question on VLOG-recording with my DVX200. I know, that I get the large dynamic range when setting my camcorder to VLOG. However, what about the color gamut? VLOG color gamut gets far beyond Rec. 709 color gamut and is close to REC. 2020. When I record in VLOG setting, do I get the large color gamut of VLOG on disk or is color gamut still reduced to Rec. 709?
Joachim

[Joachim Claus]

I got this answer from Panasonic:

Thank you very much for your support of Panasonic professional video products.
ITU-R BT.709 colour space is always applied in all record modes including V-LOG mode on the AG-DVX200.

Best regards,
--
Panasonic PASS Support Team

[James Duke]

Joachim Hi,

I have a challenge here. As I embark on making all my projects HDR and Rec. 2020, all kinds of misunderstanding show up.

1. In Apple’s “Working with Wide Color Gamut in Final Cut Pro X” there is a phrase “All log-processing settings applied to log footage
will be converted from Rec. 709 to Rec. 2020 automatically, so that you always see
the full range of colors in your source material when working in a Rec. 2020 library.”
As you found out, Panasonic (I think erroneously) decided to make DVX200 not to follow Vericam and forced 709 on VLog-L.
Does the Vlog-L media in FCPX 2020 timeline after applying Log Processing > VLog in inspector look 2020 to you?

2. I applied your Vlog-L LUT to my media and something does not look right. I am probably doing something wrong. Could you please describe in detail how you use it in FCPX?

3. Also, I just found out from Filmconvert that they apply 709 the moment you use their plugin in FCPX.

4. Do you happened to know if GH5 v2.0 Log also restricts to 709?

Thanks.

James Duke
jduke@dukehome.com

[Joachim Claus]

Hi James,

With regard to your Statements/questions:

1. If the camcorder records in color gamut BT.709, there is no way to get the wider colors as defined in BT.2020. To get the wider colors, the camcorder must support the color gamut BT.2020 or - as Panasonic Varicam - V-Log color gamut (which is even slightly wider than BT.2020.

2. I do not know Final Cut, so I cannot describe how to use it there. I use the LUT in Resolve and in Media Composer.

3. That makes sense, as your source material will probably also be in 709 color gamut.

4. As far as I know, GH5 (and GH4) with the Firmware-Upgrade only support V-Log as logarithmic exposure (log-function) to get a wider contrast ratio (up to 12 f-stops). There is no change in the color gamut. It is still 709. Until now only the varicam can be switched to V-Log color gamut.

Generally, when speaking of V-Log, there are two aspects:
- V-Log as a logarithmic exposure to get a wider contrast ratio,
- V-Log as a color gamut with much wider color range, comparable to Rec.2020.

LUT's can be created to look as both of these facts, i.e. convert a V-Log recorded file to standard Video gamma (709), and/or convert a wide gamut (V-Log gamut, Rec2020) to standard video color gamut 709. I have created a LUT which converts the color gamut from 709 to Rec2020, however, colors do not look different, because the recorded source material (709) simply has no color values beyond 709. You may consider this best with the color triangles in a color chart. BT709 is a relative small triangle which covers about 35% of the visible spectrum colors. BT2020 covers about 90% of the visible spectrum and is a much larger triangle in the color chart. If you map 709 material into Rec2020 it is just the same small triangle inside the larger triangle of Rec2020. It does not get richer colors.

I hope this helps you to understand the V-Log and Rec2020 situation a little better.

Joachim

[Gary Huff]

Originally Posted by Joachim Claus

4. As far as I know, GH5 (and GH4) with the Firmware-Upgrade only support V-Log as logarithmic exposure (log-function) to get a wider contrast ratio (up to 12 f-stops).

That is correct. Vlog-L is only the logarithmic gamma curve. For the full Vlog color gamut, the EVA1 is the only option as that has full Vlog built-in.

[James Duke]

Thank you for your answer.

I do understand that one cannot get “more colors” when the “more” was already cut off. It may be a marketing defined restrictions, because the sensor probably is wider than 709.

What I am trying to do is to have Rec. 2020 compliant (mathematically) media, even though the colors are not there.
I did not study encoders/decoders (new TV sets) behaviors when they encounter 709 media. My assumption is that they will take the dynamic range part and convert 709 limited colors into Rec. 2020 with the same limited colors.

Working in Resolve will solve all these problems because it delivers the complete “HDR/2020 thing.” I asked about FCPX, because that is where all my projects are for now.

Again, thank you for your answers.

James.

[Joachim Claus]

Hallo James,

I made some tests with Rec 2020 encoded HDR-media.

I recorded UHD/50p video in V-LOG mode (Panasonic AG-DVX200) on internal XDHC-cards.

I loaded the clips into Resolve in a project with the following settings:

Timeline Resolution: 3840 x 2160 UHD
Playback rate 50fps

Color Management:
Seperate color Space and Gamma
Input Color Space: Panasonic V-Gamut Gamma: Panasonic V-Log
Timeline Color Space: Rec 2020 Timeline Gamma: Rec.2100 ST2084
Output Color Space: Rec.2020 Output Gamma: ST2084 1000 nit

I exported the timeline for Avid AAF and imported media into Media Composer. With Display Setting to "Rec2020" MC shows all clips in their natural color with high dynamic range. Even when in BT.2020-mode, the colors are not wider, as the source material from Panasonic AG-DVX200 records in BT.709 color gamut.

I created a UHD-BD from the timeline and played it on my TV (LG OLED HDR model). When I play the BD, the TV set switches automatically to HDR-mode and displays nice colors and a wide Gamma (HDR).
When I inspect the media within the TV-set it says: UHD 3840 x 2160, BT2020, HDR.

The displayed colors look natural on the TV-set, however, due to the camcorder's internal recording limit to 4:2:0 8-bit, video shows a lot of banding in bright areas of the picture (white house walls, blue sky with clouds). Even when I used the "de-banding" filter in Resolve, this banding looks terrible on the TV-set.

So my conclusion is: HDR-video makes only sense if your records are made in 10-bit color resolution. In my case this requires external recording via the camcorder's HDMI-interface to an external recorder, such as Atomos Shogun Inferno. However, even with external recording, a wider color gamut (Rec.2020 or DCI-P3) is not achieved due to the camcorder's limitation to BT.709.

Joachim