Final Explanation of Gamma and Color Shift Problems

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Vit Reiter

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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 15, 2020 11:15 pm

Dmitry Shijan wrote:In YRGB Color managed project i suggest you don't rely on auto detection and always manually set correct input color space for each file.
I never had a problem with auto detection in DaVinci.

Plus, I don't know what gamma input video has? I'm not talking about rushies from the camera where it's obvious, but about the master video that I get to edit or QC and I need to export it with the same gamma settings as the original. Most such videos are Rec.709 Gamma 2.4. However, if I export to Rec.709 Gamma 2.4, the video loses the transfer characteristic parameter and is unusable in the pipeline. I always have to deliver the video with the transfer characteristic parameter otherwise the client will return it to me. I solve it now in DaVinci by exporting the video to Rec.709 Scene, which will retain the transfer characteristic, but I have to make it looks like the original in unmanaged color spaces environment. It would be better if DaVinci exported properly.
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Vit Reiter

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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 15, 2020 11:25 pm

Andrew Kolakowski wrote:Lost my interest in discussion with you.
I respect that, but rather you have nothing to say. How to export Rec.709 Gamma 2.4 with transfer characteristics cannot be said because it is not possible from the current DaVinci.

Even so, thank you for the discussion. Thanks!
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Andrew Kolakowski

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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Mar 16, 2020 10:28 am

Resolve already does it in only and correct way based on current possibilities. There is no other way- not sure what is so hard to understand here :D
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Re: Final Explanation of Gamma and Color Shift Problems

PostFri Mar 20, 2020 4:39 am

Here's some info for everyone: QuickTime Player uses incorrect math for gamma. That's why its images are washed out compared to correct displays in other applications. I believe Safari duplicates the incorrect math in order to save face, and FCP probably does too (although FCP 7 showed different gamma in its viewer when paused vs. playing back).

QuickTime has always suffered from profound gamma problems. From one codec to the next, and one application to the next, you never know what you're going to get. Apple realized this (translation: was pilloried for this by the higher-end production community) in the mid-to-late 2000s and doesn't seem to have learned its lesson.

So, when checking gamma, don't use Apple applications.
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Wayne Steven

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Re: Final Explanation of Gamma and Color Shift Problems

PostFri Mar 20, 2020 6:09 am

Somebody mentioned something like this, that they were a consultant or something hired in.
Last edited by Wayne Steven on Fri Mar 20, 2020 11:44 am, edited 1 time in total.
If you are not truthfully progressive, maybe you shouldn't say anything. Side topics in-line with, or related to, the discussion accepted.

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Andrew Kolakowski

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Re: Final Explanation of Gamma and Color Shift Problems

PostFri Mar 20, 2020 9:56 am

PalmerWoodrow wrote:Here's some info for everyone: QuickTime Player uses incorrect math for gamma. That's why its images are washed out compared to correct displays in other applications. I believe Safari duplicates the incorrect math in order to save face, and FCP probably does too (although FCP 7 showed different gamma in its viewer when paused vs. playing back).

QuickTime has always suffered from profound gamma problems. From one codec to the next, and one application to the next, you never know what you're going to get. Apple realized this (translation: was pilloried for this by the higher-end production community) in the mid-to-late 2000s and doesn't seem to have learned its lesson.

So, when checking gamma, don't use Apple applications.


Sorry, but this is somehow "misleading" information.
Apple's color engine (which applies to QT X, Safari etc.) is not using wrong gamma. It use about 1.96 gamma which comes from original Rec.709 spec. For this preset it's correct gamma approximation.
Problem is that files should not be tagged with Rec.709 (1-1-1), but correct standards for todays production specs.
With current, outdated tagging presets correct way is what Resolve and Baselight does, but this is quickly lost in wildness of other apps.

You are spreading more myths than info based on facts (same as never existed/understood QT gammas shift).
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Re: Final Explanation of Gamma and Color Shift Problems

PostFri Mar 20, 2020 6:03 pm

Andrew, but now the original rec709 is deprecated by to newer BT1886 that specify a gamma of 2.4 for the display... in a sense QT is wrong...
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Andrew Kolakowski

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Re: Final Explanation of Gamma and Color Shift Problems

PostFri Mar 20, 2020 9:11 pm

So introduce and set BT.1886 tag and all will be good. Why are you expecting old tag to use new value? It's reserved tag for original Rec.709 spec.
You can't change old preset as this is not they way how you do it with standards.
We don't have Rec.709 updated with new eg. HLG curve do we?
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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Mar 21, 2020 1:14 am

Will you suggest a new Bt1886/2.4 tag?

Because it's basically rec709/2.4.
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Wayne Steven

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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Mar 21, 2020 4:29 am

I read that the default now without the gamma for 709 bring specified should be 2.4 because of 1886.

My previous post on doing a common instructions, tutorials, formulas and code base is the way to introduce broad comparability in apps snd players.

You are better off writing to the standards organisation, and each tool developer to resolve this in the way I suggested before, than endlessly throwing your hands in the air. A lot of solutions suggested here are gamut limited.
If you are not truthfully progressive, maybe you shouldn't say anything. Side topics in-line with, or related to, the discussion accepted.

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Andrew Kolakowski

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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Mar 21, 2020 3:20 pm

waltervolpatto wrote:Will you suggest a new Bt1886/2.4 tag?

Because it's basically rec709/2.4.


Resolve already tags files as Rec.709 with 2.4 gamma, but this is not preserved/supported by about anything (except Baselight) due to apps not fully respecting QT spec.
It's also specific to MOV headers. h264/5/VP9 have different structure (they don't support custom gamma tag).
We want new tag options for h264/5/VP9, so files can be described properly.

Again- why do you try to call something new with proper existing spec using old one reserved for something already exiting and different?
It's "basically" Rec.709 with 2.4 gamma- is it? Can be Rec.709 2.2 as well (still present a lot), so how do you know which is which?
Whole confusion comes exactly from such an approach.
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Andrew Kolakowski

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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Mar 21, 2020 3:22 pm

Wayne Steven wrote:I read that the default now without the gamma for 709 bring specified should be 2.4 because of 1886.


Maybe in Catalina, not in any prior OSX as far as I can tell.
I will check Catalina.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Mar 21, 2020 5:32 pm

Cosmin Hodiș-Mîndraș wrote:It seems that every "QuickTime gamma bug" is experienced by people expecting QuickTime player and YouTube to look like Resolve's color viewer. Those producing for broadcast are always concerned about calibrated Rec709 professional monitors, fed by UltraStudio or DeckLink cards, and care little for computer displays. Fair enough. The thing is, I really want my YouTube uploads to look as close to Resolve as possible, even if some of my productions are intended for broadcast.

So I made a few tests, exporting QuickTime files from Resolve using several timeline color spaces. The result, as shown by macOS finder, are:
  • Rec.709 Gamma 2.4 - Color profile: (1-2-1)
  • Rec.709 Gamma 2.2 - Color profile: (1-4-1)
  • Rec.709 (Scene) - Color profile: HD(1-1-1)
  • sRGB - (1-13-1)
(What 1-1-1 or 1-2-1 mean is explained in the first post of this topic).




Any of those files, once exported from Resolve, looked different in QuickTime. Once uploaded to YouTube, those files looked different as well, low contrast and desaturated. I downloaded them from YouTube and every file had the same color profile: HD (1-1-1). The same happened when I compressed the files using HandBrake, the color profile was changed to HD (1-1-1) as well.

What's quite clear at this point is the fact that YouTube ignores the source color profile, assuming 1-1-1. So, as a consequence, I have to Cosmin Hodiș-Mîndraș.709 (Scene) in Resolve (because it exports 1-1-1 profiles), and color grade for it. But how to set Resolve to look like QuickTime Player? Enabling "Use Mac Display Color Profiles for Viewers" in DaVinci Resolve helped a bit, but not a lot, some shadows were crushed and definitely saturation looked different.

I then thought about creating a display LUT for Resolve, which mimics the QuickTime and YouTube output:
  • I created a 1728x1728px 8-bit HALD image using ImageMagick:
    Code: Select all
    convert hald:12 -depth 8 hald12_8bit.tif
  • I imported the image in Resolve, setting the timeline color space to Rec.709 (Scene) and frame size to 1728x1728px;
  • I rendered the movie using ProRes 4444;
  • I opened the rendered movie in QuickTime, and made a screenshot (quite tricky, because I had to display the movie unscaled, and macOS Catalina shows no options on "Option+Scaled in Display Preferences for the built-in display; luckily I have an external LG UltraFine display that I could put in an unscaled mode - 5120x2880px);
  • I cropped the screenshot and opened it in Lattice:
    Image
  • I resized the LUT to 21:
    Image
    Image
  • ... and I exported a .cube LUT.

After loading the LUT in 3D Color Viewer Lookup Table, QuickTime Player and Resolve viewer screenshots look identical, so I can confidently grade my timeline for YouTube, knowing that what I see is what I get.

But how about shots graded for broadcast, in Rec.709 2.4 timelines? Well, if broadcast is my main delivery and YouTube is second, I reversed the LUT in Lattice for a quick and dirty final "YouTube touch", essentially adding the "missing" saturation and contrast in one node just for YouTube delivery, on top of my main broadcast grade, temporarily switching the project to Rec.709 (Scene).

I'm not saying that this is a viable workflow for anybody. I'm quite sure that it works only on Apple's P3 displays; it's just an experiment, maybe a stupid thing to do, but the results are, for the first time (on my Macs) and at least for me, well, predictable again.

If anyone is interested, here is a link to the LUTs:
https://www.dropbox.com/s/0sux7nydfyk721w/Rec709_Scene_to_Mac.zip?dl=0



Dear colleagues, help, I want to make a LUT as in this manual. I do everything the same way and get to the stage when I do a screen shot in QT and can't figure out what to do in lattice. I get a straight gamma (linear) not as in the screenshot of the author.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 3:06 pm

In ACES (ODT set to Rec709) a H264 QT export flags with (1-2-1), where 2 is unspecified.

The automator "color profile change" doesn't work anymore under Catalina.
Also the BBC script (https://github.com/bbc/qtff-parameter-editor) is for ProRes. Only way I see is to re-encode with a colormanaged project with timeline set to Rec709.

How else to correct the wrong tags?
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 3:52 pm

Use 16.2 and set in export/advanced setting gamma to Rec.709. This sets 1-1-1 tag (and purely affects tagging itself).
Other way of fixing exiting files is hex editor. I may write up how to do it. Once you learn it will take you 30sec to do.
BBC tool is not for ProRes only. It's for MOV and also for PRoRes private headers. MOV headers are more important as most tools reads them first. You can fix them with it as well for any codec ( ProRes private headers fix is optional).
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 4:03 pm

Andrew Kolakowski wrote:Use 16.2 and set in export/advanced setting gamma to Rec.709. This sets 1-1-1 tag (and purely affects tagging itself).
Other way of fixing exiting files is hex editor. I may write up how to do it. Once you learn it will take you 30sec to do.
BBC tool is not for ProRes only. It's for MOV and also for PRoRes private headers. MOV headers are more important as most tools reads them first. You can fix them with it as well for any codec ( ProRes private headers fix is optional).


Thank you Andrew, that helps!
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 4:12 pm

I have an imac with Catalina. I noticed i still have a slight color shift when exporting in Resolve 16.2. What steps do I need to do exactly so that my final exported file in Quicktime looks exactly like the Davinci resolve viewer? Thanks in advance for all the research you guys have been doing.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 4:16 pm

Wayne Steven wrote:I read that the default now without the gamma for 709 bring specified should be 2.4 because of 1886.


You read and I've tried and it's not true at all. Nothing changed in Catalina in regards to tagging engine.
Missing tag is not treated as 2.4 gamma at all. It's same gamma as Rec.709, but different gamut.
Last edited by Andrew Kolakowski on Sun Mar 22, 2020 4:27 pm, edited 2 times in total.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 4:20 pm

Supermachoalpha wrote:I have an imac with Catalina. I noticed i still have a slight color shift when exporting in Resolve 16.2. What steps do I need to do exactly so that my final exported file in Quicktime looks exactly like the Davinci resolve viewer? Thanks in advance for all the research you guys have been doing.


Turn on "Use Mac Display color profiles for viewers" in settings. Preview should be the same for Rec.709/Rec.709 gamma and Rec.709+2.4 gamma based projects (not going to work for 2.2 gamma though).

I can also see tiny (it needs direct swap between previews to see) gamma difference for 2.4 gamma. Resolve seems to be jumping from identical to 99.9% identical preview depending on the versions.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 4:46 pm

Thanks, Andrew! I will give it a try.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 5:06 pm

Andrew Kolakowski wrote:
Supermachoalpha wrote:I have an imac with Catalina. I noticed i still have a slight color shift when exporting in Resolve 16.2. What steps do I need to do exactly so that my final exported file in Quicktime looks exactly like the Davinci resolve viewer? Thanks in advance for all the research you guys have been doing.


Turn on "Use Mac Display color profiles for viewers" in settings. Preview should be the same for Rec.709/Rec.709 gamma and Rec.709+2.4 gamma based projects (not going to work for 2.2 gamma though).

I can also see tiny (it needs direct swap between previews to see) gamma difference for 2.4 gamma. Resolve seems to be jumping from identical to 99.9% identical preview depending on the versions.


As described earlier it is not the same. It is strange but "Use Mac Display color profiles for viewers" In Resolve attempt to emulate macOS color management but result is always slightly different than in native macOS apps. It is very close but not 100% the same.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 5:35 pm

Andrew Kolakowski wrote:You read and I've tried and it's not true at all. Nothing changed in Catalina in regards to tagging engine.
Missing tag is not treated as 2.4 gamma at all. It's same gamma as Rec.709, but different gamut.



I only read that it's supposed to, doesn't mean it was implemented there (or in many places).

Dmitry has disappeared, but he was saying gamma was a display choice, rather than what is set.
Last edited by Wayne Steven on Mon Mar 23, 2020 11:08 am, edited 1 time in total.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 5:57 pm

OSX color engine reads tag and when it understands it uses it for conversion to screen profile. No tag (or unknown) means using default one which is some old one (it's somewhere on Apple QT spec sites). Nothing you can choose or have much control over.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 5:58 pm

Dmitry Shijan wrote:
Andrew Kolakowski wrote:
Supermachoalpha wrote:I have an imac with Catalina. I noticed i still have a slight color shift when exporting in Resolve 16.2. What steps do I need to do exactly so that my final exported file in Quicktime looks exactly like the Davinci resolve viewer? Thanks in advance for all the research you guys have been doing.


Turn on "Use Mac Display color profiles for viewers" in settings. Preview should be the same for Rec.709/Rec.709 gamma and Rec.709+2.4 gamma based projects (not going to work for 2.2 gamma though).

I can also see tiny (it needs direct swap between previews to see) gamma difference for 2.4 gamma. Resolve seems to be jumping from identical to 99.9% identical preview depending on the versions.


As described earlier it is not the same. It is strange but "Use Mac Display color profiles for viewers" In Resolve attempt to emulate macOS color management but result is always slightly different than in native macOS apps. It is very close but not 100% the same.


Depending on Resolve version it's either 100% the same or 99.9%. BM keeps playing with it.
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Dmitry Shijan

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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 6:06 pm

Andrew Kolakowski wrote:Depending on Resolve version it's either 100% the same or 99.9%. BM keeps playing with it.

To be honest i didn't check and compare in 16.2 just because i don't use that option at all.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Mar 22, 2020 6:26 pm

16.2 is 99.9% the same. 15.x if I remember well were 100% the same. At last some version was 100% the same. I remember this for sure.
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Mar 24, 2020 9:02 pm

It will be the ISO and not Apple that will (or needs to) release a specific BT.1886 NCLC Transfer Function tag right?
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Mar 24, 2020 9:32 pm

BT.1886 spec exists, but not sure who would be the correct body to add new tags for MOV as a format. Of course in OSX it would be Apple. There has been recently added flagging for HDR metadata in MOV. No idea who controlled/approved it. Here is small hint:
https://github.com/MediaArea/MediaInfoL ... 8cf3ada504
With other codecs h264/5 etc. it's probably down to ITU.
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Mar 24, 2020 9:45 pm

It is all about backwards compatibility. Even if in future BT.1886 will became default by Mac, what should people do with all current and legacy and current content graded with gamma2.4 and tagged with Rec709 (1-1-1)? Re encode and re tag all existing videos on planet? It is just too late to change things again... The solution is simple - Apple just need to change the way how to read Rec709 (1-1-1) gamma. It should visually match Rec709 (1-1-1) look to to legacy non color managed gamma look.
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Mar 24, 2020 9:51 pm

I doubt any serious body will do such a "fix". REc.709 flagged files can mean few different gammas. There is probably more 2.2 based files with Rec.709 tag than 2.4 based, so it's not a real solution (2.2 would be probably better choice in such a case).
With specs etc this is not the way how you do it.
Old content is "old" problem. It's not video which needs to change, just tag. Providers like Youtube/Vimeo etc. could re-flag all files if they wanted without a huge problem I assume.
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Mar 24, 2020 10:09 pm

10 years or more Apple fight against the world by using gamma 1.8 for system color management. When they gave up and move system to gamma 2.2, it took them another 10 years to fix things and match too bright system color management to normal looking Photoshop-like color management. It was all about images with ICC profiles but not about video. So i guess in next 10-20 years we may see similar story with video color management variations.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Mar 26, 2020 1:47 am

Yep no re-encoding is needed, simply a BT.1886 Transfer function NCLC tag so it can be probably transformed to a P3-D65 sRGB screen (12-13-1) in macOS 10.15.4 [as we saw in the FilmLight video]. All BT.709 (1-1-1) footage can be left as is. If the BT.1886 tag ever did get standardized I'd hope YouTube would announce support for it like they did with HDR tagging in 2016
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Mar 26, 2020 3:21 am

Isn't there any absolute space mapping standard out there where the space could then be transformed remapped to the display. That would solve many issues. On the camera side it cuts out a space to match it's performance in frame, and maps values according to transformation parameters, which should result in smaller files. The post production process redoes this to preserve it's changes while perhaps still preserving the original space and allowing reversibility of changes, and then the deliverable has a transformation to the parameters it needs. The viewer/display then maps it to it's need.

The chain is for efficient preservation at small size.
If you are not truthfully progressive, maybe you shouldn't say anything. Side topics in-line with, or related to, the discussion accepted.

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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Mar 26, 2020 4:53 am

Wayne Steven wrote:Isn't there any absolute space mapping standard out there where the space could then be transformed remapped to the display. That would solve many issues. On the camera side it cuts out a space to match it's performance in frame, and maps values according to transformation parameters, which should result in smaller files. The post production process redoes this to preserve it's changes while perhaps still preserving the original space and allowing reversibility of changes, and then the deliverable has a transformation to the parameters it needs. The viewer/display then maps it to it's need.

The chain is for efficient preservation at small size.

similar to XYZ for projectors...
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i9-7920xCPU 12c 2.90GHz Water cooled
2x 1080ti DeckLink Studio 4K (11.4)
W10-1903 - BMR St. 16.2.055
nvidia: 441.66 studio
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