Final Explanation of Gamma and Color Shift Problems

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Andrew Kolakowski

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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Oct 28, 2019 8:20 am

Just a note. 1-2-1 tag doesn't mean gamma is unknown. It just tells QTX that it should not use NCLC tag for gamma, but different one. It's up to the rendering app to set it correctly. Mac Finder doesn't show it, but it's there, so QTX doesn't guess anything. This is whole beauty as it allows you to tag your file according to real nature ( grading settings):
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Dmitry Shijan

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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Oct 28, 2019 8:53 am

Andrew, i repeat it again and again - if you want your footage look different between Resolve viewer, QTX ProRes master files and mp4 played back in VLC/ YouTube - keep fight with Rec709 specification and keep tag files with 1-2-1 gamma 2.4 and observe whole beauty of whatever you want. Only QTX player can read that 1-2-1 gamma 2.4 tag. Most other apps and hardware players on planet will ignore any tags and will read it as 1-1-1 BT.709-BT.709-BT.709
My guess Apple designed those tags long time ago as a part of QT player, and later those tags where partially adopted to mp4 h264/h265 specification to communicate with video players for Rec2020 HDR delivery.
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Andrew Kolakowski

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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Oct 28, 2019 3:30 pm

I know all of this. Just pointing that gamma info is there as many posts suggests it's QTX guess or some hard coded info.
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Dmitry Shijan

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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Oct 29, 2019 1:59 pm

:arrow: First post was updated with a lot of additional info.
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Rohit Gupta

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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Oct 30, 2019 9:20 am

Please make sure you are using macOS 10.14.6 or higher, else your viewer and Mac color management won’t be accurate.
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Dmitry Shijan

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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Oct 30, 2019 9:22 am

Rohit Gupta wrote:Please make sure you are using macOS 10.14.6 or higher, else your viewer and Mac color management won’t be accurate.


All my tests done on macOS 10.14.6. (First post updated again on 30.10.2019)
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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Oct 30, 2019 3:21 pm

Can somebody here please dumb this down really simple for a New guy trying to work through this issue? I am using a MacBook Pro and my rendered video doesn’t look exactly like it does in resolve.

It doesn’t look terrible. But it is slightly… Brighter? Maybe slightly desaturated? I really don’t know how to articulate how it looks. I notice the shadows and colors are slightly deeper… More rich when viewing in resolve. Which is the look I want.
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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Oct 30, 2019 4:22 pm

Joakley wrote:Can somebody here please dumb this down really simple for a New guy trying to work through this issue? I am using a MacBook Pro and my rendered video doesn’t look exactly like it does in resolve.

It doesn’t look terrible. But it is slightly… Brighter? Maybe slightly desaturated? I really don’t know how to articulate how it looks. I notice the shadows and colors are slightly deeper… More rich when viewing in resolve. Which is the look I want.


I had asked a guy on youtube about this issue and his solution was similar to Dmitry's. He said he'll be making a very simple video on how to work around this issue.
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Andrew Kolakowski

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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Oct 30, 2019 4:47 pm

Not much more you can do about until 'industry' fixes it properly.
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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Oct 30, 2019 6:28 pm

Nate, can you publish a link to this guy's channel for Justin, so others can look out for it? It's a shame there is not a central place to list straight forward solutions to all these problems. You could enter summary solutions in the first posts by re-editing, for future readers.
Often people deceive themselves so much they do not understand, even when the truth is explained to them.
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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Oct 30, 2019 6:32 pm

Wayne Steven wrote: You could enter summary solutions in the first posts by re-editing, for future readers.


This is a very good idea :)
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Dmitry Shijan

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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Oct 30, 2019 7:28 pm

Quick setup:

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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 2:14 am

Dmitry Shijan wrote:Quick setup:



I can’t see anything in this video. And there’s no sound.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 2:15 am

Supermachoalpha wrote:
Joakley wrote:Can somebody here please dumb this down really simple for a New guy trying to work through this issue? I am using a MacBook Pro and my rendered video doesn’t look exactly like it does in resolve.

It doesn’t look terrible. But it is slightly… Brighter? Maybe slightly desaturated? I really don’t know how to articulate how it looks. I notice the shadows and colors are slightly deeper… More rich when viewing in resolve. Which is the look I want.


I had asked a guy on youtube about this issue and his solution was similar to Dmitry's. He said he'll be making a very simple video on how to work around this issue.


Awesome
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Joakley

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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 2:21 am

I’m seriously frustrated and a little bummed out. I spent like an entire day and a half grading this thing. And when I play it after rendering it looks like somebody cranked the iso up a little bit. It also cools the image more and **** looks weak and flat.

Some dude on Facebook suggested playing it in VLC. I did that and the picture was, in fact, pretty true to what I had in Resolve. It looks quite nice. But I want others to be able to see it the way it’s supposed to be too. I uploaded it to Vimeo and it looks gross again.

I appreciate this thread, but it’s still just so much for me to pick apart. I want my goddamn video!
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 9:04 am

Joakley wrote:I’m seriously frustrated and a little bummed out. I spent like an entire day and a half grading this thing. And when I play it after rendering it looks like somebody cranked the iso up a little bit. It also cools the image more and **** looks weak and flat.

Some dude on Facebook suggested playing it in VLC. I did that and the picture was, in fact, pretty true to what I had in Resolve. It looks quite nice. But I want others to be able to see it the way it’s supposed to be too. I uploaded it to Vimeo and it looks gross again.

I appreciate this thread, but it’s still just so much for me to pick apart. I want my goddamn video!


Not sure about Vimeo, but uploads to YouTube look the same regardless, they are not affected by the new 1-2-1 tagging behaviour.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 10:56 am

Youtube doesn't care much about headers for SDR uploads.
Vimeo may be different though.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 11:56 am

Often people deceive themselves so much they do not understand, even when the truth is explained to them.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 3:41 pm

Wayne Steven wrote:Nate, can you publish a link to this guy's channel for Justin, so others can look out for it? It's a shame there is not a central place to list straight forward solutions to all these problems. You could enter summary solutions in the first posts by re-editing, for future readers.


The guy I asked has a channel called "Color Grade School" on Youtube.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 3:44 pm

Wayne Steven wrote:https://forum.blackmagicdesign.com/viewtopic.php?f=2&t=101679



These type of videos are more like part of the issue when it comes to explanations and fixes. He's a good guy but these videos are just too darn long and beat around the bush too much. There are very few channels that bring the solution straight forward and to the point. These type of guys like that Gerald guy are more concerned about making videos over 10 minutes long to have that infamous "Youtube algorithm" work in their favor.
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Dmitry Shijan

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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 3:51 pm

:!: Let's stay at topic and discuss here only Gamma and Color Shift related problems between different video players and different transcoded formats.
Explanation of different clipped highlights with different ISO settings is very very off topic.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 3:55 pm

Dmitry Shijan wrote::!: Let's stay at topic and discuss here only Gamma and Color Shift related problems between different video players and different transcoded formats.
Explanation of different clipped highlights with different ISO settings is very very off topic.

Correct. Dmitry, have you tried the new Resolve update to see if it made any changes?
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 8:14 pm

Supermachoalpha wrote:
Wayne Steven wrote:Nate, can you publish a link to this guy's channel for Justin, so others can look out for it? It's a shame there is not a central place to list straight forward solutions to all these problems. You could enter summary solutions in the first posts by re-editing, for future readers.


The guy I asked has a channel called "Color Grade School" on Youtube.


I’m familiar with that channel. And I’m pretty sure I’m subscribed. I’ll keep a lookout .
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 8:35 pm

Dmitry Shijan wrote::!: Let's stay at topic and discuss here only Gamma and Color Shift related problems between different video players and different transcoded formats.
Explanation of different clipped highlights with different ISO settings is very very off topic.



Hey man. Me again.

I’ve tried...I really have, to try and grasp what you were saying to do with settings.

Do these look right to you? The image is still messed up and render isn’t the same as preview still, but where do I need to be...as far as settings? I just want to fix this issue so I can have an accurate rendered picture.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Oct 31, 2019 10:04 pm

Dmitry Shijan wrote::!: Let's stay at topic and discuss here only Gamma and Color Shift related problems between different video players and different transcoded formats.
Explanation of different clipped highlights with different ISO settings is very very off topic.


Ok, the video was about a little more information on how Braw contributes to shifts in grading.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Nov 02, 2019 11:07 am

Joakley, why you keep spamming with same question again and again? All possible answers are described in details in first post of this topic viewtopic.php?f=21&t=101253#p560853
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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Nov 02, 2019 2:26 pm

Dmitry Shijan wrote:Joakley, why you keep spamming with same question again and again? All possible answers are described in details in first post of this topic viewtopic.php?f=21&t=101253#p560853


It’s not “spamming”. I’m trying to get crystal clear solutions. But all I see are conversations and debates about stuff that honestly is above my scope. I told you that I set the output color spaces and all that according to what you recommended in your post. I asked if I understood you correctly and set them correctly....no reply.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Nov 02, 2019 2:29 pm

First post describes crystal clear solution.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 1:36 am

Dmitry Shijan wrote:First post describes crystal clear solution.



Alrighty, so if you could help make it a little more crystal clear for me here. I’m not a colorist so some of the verbiage is beyond me.

1) you said to select rec709 for timeline color space. Ok, cool. So I’ve got Blackmagic pocket cinema camera footage...BRAW. Is the input color space and gamma supposed to be set accordingly (Blackmagic pocket cinema camera 4K)? I see that they are options.

2) What about OUTPUT color space? Rec709 as well? Somebody elsewhere said I need to choose sRGB and gamma 2.2 for timeline and output color space. Are they giving me bad info?

3) what is a CST node? Is it a node that I adjust to compensate for the crappy rendered look? And should I deactivate it before rendering?
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 3:23 am

Joakley wrote:3) what is a CST node? Is it a node that I adjust to compensate for the crappy rendered look? And should I deactivate it before rendering?

It's a color space transform node, and no, it will not solve your problem.

The problem is really a color playback engine problem. If the same file looks different in QuickTime, Resolve, and VLC, then clearly one of them is changing the image -- it's not the file. Without a color-managed output and a calibrated display -- as I've said many times -- all bets are off. You can make a good argument that sound is affected by similar factors, because speakers are so radically different on laptops, earphones, small TV sets, big TV sets, large speakers, and theaters.

The article links I posted earlier explain the core reasons for the problem. Take five laptops and play the exact same file on all five at the same time, you'll see 5 different pictures. Whose fault is that? This is the fundamental flaw with trying to make judgements on uncalibrated displays.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 3:53 am

Marc Wielage wrote:
Joakley wrote:3) what is a CST node? Is it a node that I adjust to compensate for the crappy rendered look? And should I deactivate it before rendering?

It's a color space transform node, and no, it will not solve your problem.

The problem is really a color playback engine problem. If the same file looks different in QuickTime, Resolve, and VLC, then clearly one of them is changing the image -- it's not the file. Without a color-managed output and a calibrated display -- as I've said many times -- all bets are off. You can make a good argument that sound is affected by similar factors, because speakers are so radically different on laptops, earphones, small TV sets, big TV sets, large speakers, and theaters.

The article links I posted earlier explain the core reasons for the problem. Take five laptops and play the exact same file on all five at the same time, you'll see 5 different pictures. Whose fault is that? This is the fundamental flaw with trying to make judgements on uncalibrated displays.


For what it’s worth, my monitor (laptop screen) is calibrated.

The only difference i can see is the rendered QuickTime video. When I play that same file in VLC it looks pretty much spot on with the resolve viewer. So it’s most likely a QuickTime issue, no? I uploaded the same video to Vimeo and it still looked slightly brighter and less saturated. It’s not necessarily “color” shifts or hues or whatever. It’s like somebody bumped the brightness up just a smidge. And took the sat down a hair.

It’s small...but huge at the same time. The image isn’t ruined per se. But when I spend hours grading the picture, creating a nice dramatic look, that slight bump in brightness can change the entire mood of a short film...or music video...or whatever.

You mentioned a color managed output. In dmitry’s post he said (non color managed). This is all very conflicting and confusing. Especially for a guy like me. I’m not a colorist. I just want to make cool stuff. And I want any joe blow who opens that Vimeo link to see what I see. And what I spent a good deal of time making. I understand that different devices display differently. But I at least want to be in the ballpark and have it look pretty damn close.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 6:52 am

Joakley wrote:For what it’s worth, my monitor (laptop screen) is calibrated.

As far as I know, it's not possible to calibrate a laptop display. Tell me how you calibrated it and what probe you used.

Believe me: you're endlessly chasing your tail on this, and your world is never going to be the way you believe it can be. Read the links I posted on color management until it sinks in. Every single person who watches Vimeo will be watching via a different browser and OS, and since each of those can and will change playback, and nobody watching is going to have a calibrated display, nobody is ever, ever going to see the same image that was approved in final color.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 12:03 pm

YRGB (sometimes also named as "non color managed") is just a name of timeline settings. It actually can be color managed, but you need to do it manually with CST (Color Space Transform) nodes.
YRGB Color Managed is a sort of simpler timeline settings. It do all color transforms under the hood and so may look more friendly for beginners but in real life it is less flexible for advanced work.

Joakley, you really need to spend some time watch some basic Resolve video tutorials course to understand overall how basic tools works in Resolve. After that you may look for some more advanced tutorials that describes in details different tools and manipulations. Next you need to learn some basic things about Color management and Color spaces in digital images world. Read articles provided earlier by Marc Wielage as well.
Resolve is not a simple app, it usually requires months and years of learning before do something decent. And from your questions i see again that you didn't ever read full article in first post.

Also note that this thread is not about step by step workflow, it is just explains some specific points in workflow that may affect gamma shifts.
Resole is very flexible and so you can do same things in dozens of different ways with different tools. It is up to you how to setup your workflow how to use knowledge from first post to avoid gamma shifts.

P.S. Worst case scenario situation for beginners - BM RAW camera + Resolve + new Apple computer with wide gamut P3 screen. 3 complicated professional tools that looks like consumer toys at first time, but in reality require huge amount of stills and knowledge to provide nice looking result.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 12:50 pm

Marc Wielage wrote:
Joakley wrote:For what it’s worth, my monitor (laptop screen) is calibrated.

As far as I know, it's not possible to calibrate a laptop display. Tell me how you calibrated it and what probe you used.

Believe me: you're endlessly chasing your tail on this, and your world is never going to be the way you believe it can be. Read the links I posted on color management until it sinks in. Every single person who watches Vimeo will be watching via a different browser and OS, and since each of those can and will change playback, and nobody watching is going to have a calibrated display, nobody is ever, ever going to see the same image that was approved in final color.


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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 12:52 pm

Dmitry Shijan wrote:YRGB (sometimes also named as "non color managed") is just a name of timeline settings. It actually can be color managed, but you need to do it manually with CST (Color Space Transform) nodes.
YRGB Color Managed is a sort of simpler timeline settings. It do all color transforms under the hood and so may look more friendly for beginners but in real life it is less flexible for advanced work.

Joakley, you really need to spend some time watch some basic Resolve video tutorials course to understand overall how basic tools works in Resolve. After that you may look for some more advanced tutorials that describes in details different tools and manipulations. Next you need to learn some basic things about Color management and Color spaces in digital images world. Read articles provided earlier by Marc Wielage as well.
Resolve is not a simple app, it usually requires months and years of learning before do something decent. And from your questions i see again that you didn't ever read full article in first post.

Also note that this thread is not about step by step workflow, it is just explains some specific points in workflow that may affect gamma shifts.
Resole is very flexible and so you can do same things in dozens of different ways with different tools. It is up to you how to setup your workflow how to use knowledge from first post to avoid gamma shifts.

P.S. Worst case scenario situation for beginners - BM RAW camera + Resolve + new Apple computer with wide gamut P3 screen. 3 complicated professional tools that looks like consumer toys at first time, but in reality require huge amount of stills and knowledge to provide nice looking result.


I read right up to “solution” (part 6 or whatever)
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 1:23 pm

Marc, I'll put a spin on that. On my Q series Samsung, the built in Netflix app seems to receive a more tailored to the screen version of streaming, YouTube probably too. I have a fairly advanced set top box as well, and it seems via the built in TV app, it is more aware of how it should be portrayed to the TV's nuances. I imagine they might have a database for various models to tailor the image. Calibrated accurately, no, but to the average user it might help.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 1:30 pm

Marc Wielage wrote:
Joakley wrote:For what it’s worth, my monitor (laptop screen) is calibrated.

As far as I know, it's not possible to calibrate a laptop display. Tell me how you calibrated it and what probe you used.

Believe me: you're endlessly chasing your tail on this, and your world is never going to be the way you believe it can be. Read the links I posted on color management until it sinks in. Every single person who watches Vimeo will be watching via a different browser and OS, and since each of those can and will change playback, and nobody watching is going to have a calibrated display, nobody is ever, ever going to see the same image that was approved in final color.


You can die trying to sort this out, but...
this is not an explanation for the same file looking differently depending which player you use. Screen is the same in this case and it doesn't matter if it's calibrated or not!
It's slightly different problem.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 5:03 pm

Part 6. The solution:

If looking ahead, the quick solution for this problem - do NOT use gamma 2.4 in DaVinci Resolve Timeline project settings. Always set Timeline gamma to Rec.709 (Rec.709 (Scene)) and adjust final desired gamma look with CST Node or manually with gamma slider wheel whatever you like.


1) if I have alexa files (for example) and i color in AlexaLogC/AlexaWideGamut I want and need the timeline to be at that logarithmic space, so all the CST are coherent.

2) that settings (as explained elsewhere) serve too many purposes: define your color space (for coloring purpuses in the internal CST of resolve) AND tag the out quicktimes files AND used to do XYZ conversions for producing DCP. That's simpy a recipe for unmitigated disaster.

3) you're confusing rec709 (scene) that is Scene referred capture data to bt1886 that is display referred data presentation: in a QT a bt1886 value should be setup if you color in a bt1886 environment

4) I'm with Andrew: BT1886 IS the standard for reproducing signals. peroiod. it is well defined in the document:
https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.1886-0-201103-I!!PDF-E.pdf
709 gamut primaries and 2.4 output.

5) yes the electro-mechanical panel a tv manufacturer buy might have a base gamma of 2.2, but that means squat: you're not just pushing your quicktime to that panel, the TV manufacturer does a correct 2.2 to 2.4 gamma math before sending the signal to the panel.

6) I work (and worked) at fotokem, keep me posted, EFilm, Co3, Encore, and I can assure Technicolor have the same settings in their sony X300: we use 709/gamma 2.4 as for the BT1886 specification. No 2.2 nonsense.
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Joakley

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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 5:48 pm

...and this is what I meant when I said I was looking for a clear solution. There seems to be some dispute, especially among all of you pros who obviously understand more than me, a lowly hobbyist. I just need solution, or at least a workaround...as an average joe. My stuff isn’t going to the silver screen or on Netflix or anything. Vimeo is about it for me. My video plays “accurately” (as in what I color graded to in resolve) in VLC. But on qyicktime, and after uploading to Vimeo, the image is brighter.

And yes, as mentioned before, my laptop has been calibrated. Whether or not it’s possible or if it’s truly calibrated is...whatever. The spyder5 Pro came up in many topics regarding calibration (PCs and Macs included). And it is designed to be comparable with laptops. Anyway, that’s kind of besides the point.

When I cut, edit, and grade a video in FCPX, for example, the rendered image is still the same...regardless of whether or not my screen is calibrated. At no point have I exported a video in final cut and said “this looks way brighter than the picture I just spent hours color grading”.
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Dmitry Shijan

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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 5:53 pm

waltervolpatto wrote:1) if I have alexa files (for example) and i color in AlexaLogC/AlexaWideGamut I want and need the timeline to be at that logarithmic space, so all the CST are coherent.


You can grade within AlexaLogC/AlexaWideGamut and same time your Timeline may be set to Rec709. Timeline in YRGB project is sort of passthrough channel.
Timeline settings in YRGB project have no any affect on Resolve image preview.
- Timeline settings only define output tags.
- Also CST nodes use Timeline settings if you choose "Timeline to ..." in CST node.
- Timeline settings also have no any effect if you set color space/gamma ins and outs manually in CST node.
- Timeline settings also used by “Use Mac Display Color Profiles for Viewers” in DaVinci Resolve Preferences->System->General. So if you set Timeline to AlexaWideGamut, use CST node to transform final result to Rec709 and turn on “Use Mac Display Color Profiles for Viewers” - you will see mad oversaturated colors. Because “Use Mac Display Color Profiles for Viewers” expect AlexaWideGamut but you actually feed to it Rec709.
“Use Mac Display Color Profiles for Viewers” also afefcts only preview. It will not affect actual pixels data on Rendered video.

You can set timeline to any settings and grade as usual in Log gamma. All tools will work in Log gamma. I described sample setup with REDWide Gamut/RED log3G10 within Rec709 timeline in this video:



As i described earlier, if your final delivery is different from YouTube/computer/BluRay player, you may use different timeline settings.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 5:58 pm

Andrew Kolakowski wrote:
Marc Wielage wrote:You can die trying to sort this out, but...
this is not an explanation for the same file looking differently depending which player you use. Screen is the same in this case and it doesn't matter if it's calibrated or not!
It's slightly different problem.



^^^ this right here is what I’m trying to articulate. Whether my image color is completely bananas and inaccurate is beside the point.

My video looks different. But it’s not. I can stick the QuickTime video right back into my resolve timeline and it matches the original. And the difference isn’t even really in the color, per se. It’s just brighter. And flatter.

So far, the more useful tips have been to sort of “compensate” for this by sticking a node at the end, lifting the gamma (kind of a blind move), and grading to that...and then disable that node before export.
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Dmitry Shijan

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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 6:02 pm

Some browsers are support color management for video, some not. Firefox vs Safari produce same difference in gamma as VLC vs Quicktime.

It was explained in first post.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 6:41 pm

You can grade within AlexaLogC/AlexaWideGamut and same time your Timeline may be set to Rec709. Timeline in YRGB project is sort of passthrough channel.


factually incorrect: the timeline setting is used actively in two cases at least:

1) if you use a OFX color transform, that is the default (that can be overridden).

2) more important, if you set on a single node to a different color space and gamma (for example to do a linear light math to it) you absolutely use that setting for a conversion therefore has to be coherent with the color space (log in my case) that you're using in the main color environment.

still it interfere with the creation of DCP and tagging of quicktime files.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 6:45 pm

Look, this thread keeps coming up in view posts. Can you guys suggest to Joe, a happy way to tick all the boxes/stack the flags, so that users will get a reasonable image on most software and hardware (if calibrated)? It doesn't have to work perfectly and not work in all instances, but as long as it is as good as it gets, so to speak. If it doesn't work, users will just have to get used to learning to use better players or buy better hardware.
Often people deceive themselves so much they do not understand, even when the truth is explained to them.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 6:47 pm

waltervolpatto wrote:
5) yes the electro-mechanical panel a tv manufacturer buy might have a base gamma of 2.2, but that means squat: you're not just pushing your quicktime to that panel, the TV manufacturer does a correct 2.2 to 2.4 gamma math before sending the signal to the panel.

6) I work (and worked) at fotokem, keep me posted, EFilm, Co3, Encore, and I can assure Technicolor have the same settings in their sony X300: we use 709/gamma 2.4 as for the BT1886 specification. No 2.2 nonsense.



6) that's because you have the environment set to 2.4 gamma...my environment is 2.2 for some specific reasons and my DCPs turn out with a different gamma look unless I use Gamma 2.2 because Resolve assumes 2.4 environment and does the DCI science based on that. Most users have 2.2 gamma displays. h.264/265 exports look the same regardless of the gamma setting...

5) TVs have been professionally calibrated to the 2.2 gamma for ages (that has changed now with BT 1886, but where once they would swear a movie looked "spot-on" after G2.2 calibration, now they swear the same movie looks even more spot-on watched at 2.4 gamma :roll: ). TVs have been (and most still are) coming from the factory with somewhere around the 2.2-2.3 gamma even though BT 1886 has been out for some time now, but, frankly, very late in the game...and TVs normally don't take tone mapping action on the gamma tag unless it's an HDR signal. Windows don't either. It looks as if it's a Mac-specific thing to properly match the gamma look of the tagged 2.4 environment on a Mac with gamma x.x display.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 8:59 pm

Here is another very simple video illustration.
Please note, i am not a expert or professional who works full day on high budget movies grading. I just learn Resolve same as most of you, and all i wrote here only based on my own comparative tests.

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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 03, 2019 9:21 pm

Mario Kalogjera wrote:... It looks as if it's a Mac-specific thing to properly match the gamma look of the tagged 2.4 environment on a Mac with gamma x.x display.


Yes, but unfortunately color engine system is not perfect and needs to be changed to be more up to date.

Examples:
- no standard option to flag 2.4 bassed files,
- if you use 2.2 gamma flag OSX does not recognise it (even if it's a standard option and been there for ages)

What worse:
--transfer <integer|string>
Specify transfer characteristics. Default undefined (not signaled)
bt709
unknown
reserved
bt470m
bt470bg
smpte170m
smpte240m
linear
log100
log316
iec61966-2-4
bt1361e
iec61966-2-1
bt2020-10
bt2020-12
smpte2084
smpte428
arib-std-b67

these are options for fairly new h265 standard. Where is the option to flag files graded to 2.2 or 2.4 gamma (which cover about all files in the wild, except HDR ones)? I see so many useless options and yet those which are most needed are just not here. Can anyone tell me why?
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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 04, 2019 7:40 pm

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 use Rec.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
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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 04, 2019 8:06 pm

It's not stupid way if you just want to match Resolve and youtube prview. I used same technique.
You can also grade on proper monitor to 2.4 and at the end add LUT just for export for youtube needs.

It should be possible to do precise LUT, adjustment is 2.4 gamma to 1.96.
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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 04, 2019 8:23 pm

Rohit Gupta wrote:Please make sure you are using macOS 10.14.6 or higher, else your viewer and Mac color management won’t be accurate.


Why at some point Rec.709 2.4 gamma project exports started to look slightly different than QT X preview? In older Resolve versions after manual QT tagging to 2.4 gamma they were identical. Now flagging is correct, but preview is slightly off :D
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