Final Explanation of Gamma and Color Shift Problems

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Joakley

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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 04, 2019 9:40 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 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



Wow.

I’m kinda tracking what you did...as far as creating LUTs to compensate for this shift.

A lot of work that I couldn’t pull off.

Anyway, so as far as using this LUT, you essentially just add it to a final node on your video and render?

You said the image in resolve and the QuickTime video were identical. Before rendering, did the image in resolve viewer look OVER saturated, darker, etc? To adjust for quicktime’s brightening and desaturatimg?
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Cosmin Hodiș-Mîndraș

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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 04, 2019 10:04 pm

Joakley wrote:Anyway, so as far as using this LUT, you essentially just add it to a final node on your video and render?

That's one way to use it (just remember to turn it off once you're ready to render your timeline). Another way would be to load it in Project Settings > Color Management > 3D Color Viewer Lookup Table.
Joakley wrote:...Before rendering, did the image in resolve viewer look OVER saturated, darker, etc? To adjust for quicktime’s brightening and desaturatimg?

If you apply the LUT to the last clip node (or a timeline node), having all your grades under that LUT, then yes, as soon as you disable the "QuickTime compensation LUT" everything will look oversaturated and contrasty in Resolve.

It's not a problem with QuickTime, though, so you're not adjusting for QuickTime's faults (as explained at the beginning of this thread, including the linked tutorial from Baselight). Resolve doesn't expect you to use the GUI viewer, but a calibrated, broadcast monitor to judge your grade. Also, I guess Resolve doesn't (yet) have a clear workflow for YouTube delivery or computer screens in general. I mean, rendering a 1-2-1 color profile using the YouTube preset in Delivery page, knowing that YouTube is going to ignore it and assume 1-1-1, is just not working as one would expect.
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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 04, 2019 11:43 pm

Resolve viewer is correct, same as QTX.
It's all other apps and providers which remove proper eg. 2.4 gamma flagging and replace it with incorrect Rec.709 tag. This gives wrong information about the file for OSX color engine and your eg. youtube preview is different and wrong.
Problem is simple- description of the file is different than its real nature ( settings which it was graded to). Until few companies don't do us a favour and introduce up to date flagging (and respect it) this problem won't be ever solved properly.
With wide gamut displays and HDR this is now showing off much more than old days and needs a proper industry wide solution.
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Joakley

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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 04, 2019 11:59 pm

Andrew Kolakowski wrote:Resolve viewer is correct, same as QTX.
It's all other apps and providers which remove proper eg. 2.4 gamma flagging and replace it with incorrect Rec.709 tag. This gives wrong information about the file for OSX color engine and your eg. youtube preview is different and wrong.
Problem is simple- description of the file is different than its real nature ( settings which it was graded to). Until few companies don't do us a favour and introduce up to date flagging (and respect it) this problem won't be ever solved properly.
With wide gamut displays and HDR this is now showing off much more than old days and needs a proper industry wide solution.


I’m not sure which version of QuickTime I’m using, but would QuickTime X give me the same (correct) look when I open the rendered video?
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 05, 2019 8:53 am

It will but only for few combination of Resolve RCM setup, eg. Rec.709 2.4 gamma (with a tiny difference which is probably Resolve bug), P3 2.6 gamma, Rec.2020, sRGB (if I remember well).
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 05, 2019 9:21 am

Interesting question, is there a HDR format you can publish in that various players and hardware will down concert to a normalised SDR version, effectively solving a few issues?
aIf you are not truthfully progressive, maybe you shouldn't say anything
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cOften people deceive themselves so much they do not understand, even when the truth is explained to them
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Wayne Steven

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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 05, 2019 9:23 am

Actually, also. Is there anyway to sense the target and load a profile for that target (different players, screens and other hardware)?
aIf you are not truthfully progressive, maybe you shouldn't say anything
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cOften people deceive themselves so much they do not understand, even when the truth is explained to them
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Dmytro Shijan

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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 05, 2019 12:07 pm

Wayne Steven wrote:Interesting question, is there a HDR format you can publish in that various players and hardware will down concert to a normalised SDR version, effectively solving a few issues?


Quick answer - no.
Different players normalise Rec2020 HDR to SDR gamma and colors in very different way. In most cases image looks strange and very far from original Rec709 SDR master. Technically most HDR gammas can not be reversed to SDR without data loss.
Only HLG curve format 100% compatible with SDR, but i didn't done any deep tests with it.
HDR format also require at least 10bit master and decent compression because wide color spaces and log gamma transformations in real time produce a lot of banding if source is 8 bit depth. In reality even 10bit is not enough there.

Same time most current players can read Rec2020 color space tag and normalise it to Rec709 or any other monitor color space rather ok.
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Wayne Steven

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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 05, 2019 2:15 pm

Ok. So your first paragraph said player's don't normalise down well, and last paragraph you say they do a good job. What do you mean by each Dimitry?

Also, there is no ability to have meta profiles for each player, so a player picks the one relevant to it, or using embedded code, the player is given the correct profile (Andrew might know that one)?

I've seen issues just trying to push HDR around in a TV it's so marginal. I agree about bit depth. I have a high end TV, and I get banding. I wish they had gone at least 12 bits in HDR specs, 16 bits better, then a use can push things around. However, I think a solution here is to find a way that is going force an outcome for most users setups. Say hgl did work in confirming to SDR, that would be great. I don't mind some data loss, as long as it is in the right place, like clipping to the nearest 8 bit level. Is there any system where an older setup understands rec2020 as rec709 etc. What is vitally important for workflow, is to reduce the amount of deliverables for the maximum quality, rather than a deliverable for virtually every problems setup plus normals. If a subset of strategies can solve all credible exceptions, that would be great.

Waiting for a iPhone to come, to test out some of latitude and noise stuff in the coming Year (I think it is a reasonable but noisy phone that over 15 stops might be extractable from). Is there a decent latitude testing strategy I could adopt without buying a $2k+ latitude chart? Actually, I'm thinking if I had a gradient filter of known specs, I could just examine light through that on the waveform and where I can not determine the upper of lower edge clearly enough, that point along the axis gives me an effective reasonable limit value of exposure. I could leave clear on the top edge, and blackout on the bottom (an issue). However, if I could tune a point light source and run it under the plate. I am also interested in an experiment to extend dynamic range on the thing.

Still locking out fur a pocket too.
Last edited by Wayne Steven on Wed Dec 25, 2019 5:27 am, edited 1 time in total.
aIf you are not truthfully progressive, maybe you shouldn't say anything
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cOften 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 Nov 06, 2019 5:41 am

Wayne Steven wrote:Ok. So your first paragraph said player's don't normalise down well, and last paragraph you say they do a good job. What do you mean by each Dimitry?
Dimitry was making a distinction between the EOTF transform — HDR10 to SDR — which various apps will not tonemap consistently, versus a color space transform — REC2020 to REC709 — which most apps will transform correctly.

The REC2020 color space and the HDR10 EOTF are two totally separate things. And while you often will see them together as a file with HDR10 EOTF in the REC2020 colorspace, you could just as easily have HDR10 EOTF with a different color space, like P3 D65 or PC DCI.
Or you could have a file in the REC2020 color space with a log gamma, if for example, you recorded on a Canon C200 Mark II set to REC2020 in CanonLog3.
Last edited by Jamie LeJeune on Wed Nov 06, 2019 5:15 pm, edited 1 time in total.
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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Nov 06, 2019 12:15 pm

Yep, true Jamie, I'm conflating the two, I should have suggested BT2100. Freakin hard after midnight.

Anyway, so colour will carry over, will gamma HLG be interpreted properly in the players? Tone mapping tends not to be standardised in implementation of displays anyway, displays have their own interpretation. Intent is what we should look for in a situation like this, not necessarily exactness in every case, as long as the errant players are close.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Nov 07, 2019 1:14 am

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.


Does YouTube re-encode? in that case it can butcher the flag or misinterpret the original one....
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Nov 07, 2019 3:15 am

Here is another temporary solution to fool Appe video color management and match QuickTime/Safari to VLC/Firefox/Resolve non color managed viewer look.
You need to use original Rec709 profile with Rec709 gamma as monitor profile. In this situation input and output for QuickTime color management became the same Rec709.
This is not for wide gamut P3 displays. On P3 display you will see oversaturated colors same as if you use VLC.

Download "HD 709-A" profile here https://www.sebastianleitner.com/HD709-A.zip



Comparative test animation:

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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Nov 07, 2019 3:59 am

And here is a trick. If you try to generate custom profile and choose Rec709 in calibration application settings, it will create different kind of Rec709 which will not match to Apple video color management Rec709, and will not eliminate gamma and colors shift between QT and VLC.
Here are some examples:

HD 709-A profile based on gamma 1.961 from Sebastian Leitner video:
Image

Rec709 profile from Elle Stone's profiles pack:
Image

Rec709 profile generated in DisplayCAL:
Image
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Nov 07, 2019 4:24 am

And here is explanation about gamma 1.961: https://forums.developer.apple.com/thread/113337

Why does Apple use simplified 1.961 gamma instead of precise ITU-R 709 transfer function?

fumoboy007
Feb 2, 2019 6:30 PM

(For Apple folks: rdar://47577096.)

# Background
The Core Video function `CVImageBufferCreateColorSpaceFromAttachments` creates custom color profiles with simplified transfer functions instead of using the standard system color profiles. Let’s take ITU-R 709 as an example.

The macOS `Rec. ITU-R BT.709-5` system color profile specifies the transfer function as

f(x) = { (0.91x + 0.09)^2.222 where x >= 0.081
{ 0.222x where x < 0.081

The Apple-custom `HDTV` color profile created by the above Core Video function specifies the transfer function as

f(x) = x^1.961

My understanding is that `x^1.961` is the closest approximation of the more complex ITU-R 709 transfer function.

# Questions

1. Why use a custom color profile with a simplified transfer function rather than the official specification?

- Was it done for performance?

- Was it done for compatibility with non-QuickTime-based applications?

- etc.

2. Speaking of compatibility, there is a problem when an encoding application uses the official transfer function and the decoding application uses the approximated transfer function. I tested this using two images. One image uses the `Rec. ITU-R BT.709-5` color profile. The other image is derived from the former by assigning the Apple-custom `HDTV` color profile. The latter image loses the details in the darker areas of the image. Why go to the trouble of approximating the transfer function when the approximation isn’t that great?

3. Are the Apple-custom color profiles also used for encoding? Or are they only for decoding?

4. Another thing that concerns me is that the Apple-custom `HDR (PQ)` and `HDR (HLG)` color profiles use the same simplified transfer function of `f(x) = x^1.801`. Isn’t the whole point of the PQ and HLG standards to define more sophisticated transfer functions? Doesn’t simplifying those two transfer functions defeat their purpose?
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Nov 07, 2019 6:52 am

Good stuff guys.

I would really like to get Apple's official statement on this.

Imagine a world where this actually get fixed. And by "fixed" I mean "get everybody on the same page".
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Nov 07, 2019 11:12 am

At the moment you can only dream about it.
Took few years for Nvidia to use proper Rec.709 vs. Rec.601 matrix depending on resolution.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Nov 07, 2019 4:10 pm

If someone want to test on wide gamut Apple displays, here are gamma Rec.709 and Display P3 profiles with gamma 1.961 generated in DisplayCAL Synthetic ICC tool. They are v2 ICC profiles so they are more compatible with software that can not support more modern v4 ICC profiles:

:arrow: https://www.dropbox.com/s/vmxlgkitvusmi ... 1.icc?dl=0
:arrow: https://www.dropbox.com/s/4qgbmrz5165c7 ... 1.icc?dl=0

It is recommended to use those profiles only for video monitoring because UI and all other images will look darker if use these profiles.
As i remember in old days before color management started to affect macOS UI, it all have same deeper gamma look.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Nov 07, 2019 5:23 pm

Thanks Andrew, I knew the computer industry were such ..... but NVIDIA too. What's the point. Unfortunately the content producer is going wear it when things look wrong, when the player/hardware producer should be getting the stick. I've seen this most my life, being around top people who efficiency, and in my case correct efficiency, is paramount, to see garbage design just increase and increase in the industry, spread to phones, appliances and TV's. I've been contributing to industry design since I was around 16.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Nov 07, 2019 8:02 pm

And thanks to magic number 1.961, seems i found that highly technical thread about macOS video gamma adventures i mentioned in earlier posts. By the way it was started by same fumoboy007, who is the developer of mpv media player. Problem is going back to 2017, and if you dig other forum threads to 2013 and seems like forever in past. So seems Apple just don't care about this problem.

https://github.com/mpv-player/mpv/issues/4248

Some basic thoughts from that thread:
- Apple decide to modify classic CRT displays Rec709 video gamma reading which was designed for dimmed (studio/cinema) environment to match visual appearance for bright (office/daylight) environment.
- No one knows if Apple video gamma correction value was taken from some subjective scientific tests or if it was just taken from some random value by hired coder who don't care.
- Apple do NOT preserve ICC specification for video color management.
- Because this gamma correction don't preserve any specification, and formally based only on Apple's fantasy and imagination, everyone outside Apple decide to reject this gamma correction method for video.

P.S. For me subjectively that "Apple way" video gamma corrected for bright environment always looks very *******, so i never accept that "look" as reverence.
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Re: Final Explanation of Gamma and Color Shift Problems

PostThu Nov 07, 2019 10:58 pm

There is nothing magical about this number. It's calculated from original Rec.709 spec for recording devices:

"The power function of the majority of the gamma curve is 0.45, but because it is offset by the linear section the resulting equivalent gamma is more approximate to 0.50-0.53 (the inverse of which is approximately gamma 1.9-2.0 to convert back to linear)."

1.961 is about middle of this range (1/0.51)

Problem is that this value should not be really applied to "displays". We have proper BT.1886 spec for this or "working well for many" 2.2 value.
There is a 2.2 standard flag in QT spec (value 4), but Apple color engine doesn't recognise it for whatever reason, so files flagged this way (Resolve does it now) are not converted properly to screen profile.
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Re: Final Explanation of Gamma and Color Shift Problems

PostFri Nov 08, 2019 5:59 pm

If you only need to color grade and don't want that color shift, the best thing to do is go back to Resolve 16.0 It works like a charm. BM needs to update 16.1.1 with whatever export settings 16.0 has because that one works really well when exporting.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Nov 09, 2019 12:01 am

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.

At the risk of swimming through this stream of manure once again...

Cullen Kelly has written a terrific piece for Frame.io:

Grading for Mixed Delivery: Cinema, Home, and Every Screen in Between
https://blog.frame.io/2019/10/14/gradin ... -delivery/

and I think it covers the issues and the solutions very well. Understanding color management is also helpful:

Color Management for Video Editors
https://jonnyelwyn.co.uk/film-and-video ... o-editors/
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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Nov 09, 2019 3:38 am

Sounds like the industry needs to redo the standard so it sticks to graded, with second metadata for viewing on different players and displays, but also the user can set their own target preferences (something I've been pushing on displays for years, not just passive display controls but also individuals user look targets where it follows colour balance, and reasonable light balance, but is pretty much shiftable to what the user wants otherwise). So, if a user wants everything to look like an edgy mess, or like a dull desaturated movie they can, just by selecting their prefered look setup through a switch control, and then go back to normal, a more advanced form of the standard, natural and dynamic paradigm that user can set to their own different physiological psychological needs which is dictated by their health and biological functioning. In other words, they set the grade. The next level of development.

What Apple has done, is set something higher when the user atnyhevdane time may well be having their displays turned up already for different content, so it will vary continuously between content, if so am reading it right.

I remember many many years ago, comparing video footage between players, the QuickTime ussuslly had the unnusual/not very useful, result. Definitely an ongoing issue.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Nov 09, 2019 9:08 pm

Problem is that Apple is more correct than others (just not fully and bit outdated).
Try eg. previewing P3 master on PC with standard monitor.
What Apple has done (or trying to do) is correct. Grade file on reference screen, tag it properly and it will look fine (as for home accuracy) on their devices. They will properly convert it to screen profile. It's others who ignore all flagging etc. and apply same math to files which are graded to totally different standards.
It's time to abandon 1 math for every file approach, which worked up to some degree in old days with barely Rec.709 gamuts etc. screens.
Again- look how long it took Nvidia to apply correct reverse matrix for displaying HD vs. SD videos :)
Accuracy gives no additional money for MS or Apple so they don't give a crap about whole problem.

Home users not going to have screen for Rec.709 video, screen for P3, screen for HDR etc. (or even keep switching 1 good screen manually to given standard- they are not studios). They need proper color managed automated preview, so they can watch fairly accurate videos on whatever screen they have. Those with good screens will see them closer to correct look and those with crap screens with less (but this is different issue). It's a must in todays reality where we have few standards (not just 1 or 2).
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Re: Final Explanation of Gamma and Color Shift Problems

PostSat Nov 09, 2019 9:29 pm

I agree that color management for video is important and soon or late it will be something must have in the world of monitors with random color spaces and HDR gammas, but as it was described here viewtopic.php?f=21&t=101253&p=566641#p565898 Apple reads simplified 1.961 gamma instead of precise ITU-R 709 transfer function which is produce gamma shift. My guess this brighter gamma "look" is another victim of Apple's attempts to unify their desktop and mobile platforms:
Brighter gamma look may be great for tiny smartphone screen when watched outdoors.
Brighter gamma look may be OK for small laptop screen when watched outdoors or at some kind of street cafe.
Brighter gamma look is NOT ok for large grading display in studio environment or any other average dimmed room for color grading or video editing.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 10, 2019 2:40 am

I agree. I have the NVIDIA previous "best in the world" media player, and they only recently support rec2020, which is now an old standard. The market is quality, but look at the failure of the media pc. The concept is great, the delivery is poor, so it flunks, they close down like sulky Baby man, and movie onie, like they still kings, instead of spending relatively little money making it work properly, and satisfying people.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 10, 2019 3:30 am

Seperate post for the important stuff, on how the industry can set standards which can be picked up by any media player, Dimitry.

Sorry, I thought it was just Apple failing to do it right. But, the industry needs to set standards so that you select whatever delivery gamma etc, by vales that define any gamma, or variation, any bit depth, any lighting range per line even, any pixel format etc (even mosaic pixels and their interpretation) precisely and concisely. Then transformation matrix with code and data for each, and transformation matrix with code and data for the display environment brightness, and the display is handled by the manufacturer, and or player (where the market might make custom profile for models). Now, players just plug in the transformation matrix, data and code freeware open source and obtain near universal standardisatiom of pre user quality (the user changes the look to their liking locally).

But in the past I had put out their individual looks for individual users, like I suggested in a post above, where it intelligently transforms the look to one of the individuals prefered looks (the user modifying base looks to create his own button instant switchable looks, so they can instantly choose to switch based on content. I have got my TV setup for 4 looks, by playing around with the built in high quality look functiond, but it's not very intelligent or comprehensive. My personal looks tend to be extreme but still tastey viewable. I still want to push more colour up and out into the rec2020 colours space though, with better brightness control so I can avoid pushing up the promotional be backlighting of the Q7 that doesn't seem to understand that if you got a zoning system which matches the black bars you should independently light the black bars, and stick subtitles there dimmed, do as to maximise blackness of blacks in the scene. Some dimming settings almost get the blackness thing, after I play with the settings.

I reserve some of my thinking for commercial design. So, there is one big thing for codecs I have touched on previous years elsewhere, which solves everything, except for players etc and codecs, where you define everything inside the encoded file. I am not saying my more advanced commercially ideas on this, but it solves everything. But having things defined inside the encoded file takes it off the player and hardware. You could have an entire movie encoded as 16 bits inside a bit of pixel if you wanted such a silly thing, flexibility. But you can walk away from all these problems with systems like that, you can just use and transfer the physical profile of the grading environment in the encoded file to the user display for them to interpret to the user's wishes. This whole director's intent over the top of user's eyeballs (forcing/enslaving) is just a heap of.., not many of them appear to be extremely good at it. In 3D animation they put out feelers for companies bidding to supply their version on the look, they should just try that in cinema where each company supplies samples of multiple looks, then they can select a look to work off of with minimal outside intervention or domination until the end. Sorry for the aside, I am just so offended at how grading has gone since our end of digital cinema camera, dead dog look style came out. But this brand tends to stay away from it.

I know some of you guys will know people on standards committees you could point here.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 10, 2019 4:56 am

Wayne Steven wrote:I agree. I have the NVIDIA previous "best in the world" media player, and they only recently support rec2020, which is now an old standard.

Note that, as far as I know, there isn't a monitor in the world that can hit every aspect of Rec2020. Not yet, anyway. Even Sony's $35,000 BVM-X310 has an asterisk next to their Rec2020 color gamut claim which says:

"Note: BVM‑HX310 does not cover the ITU-R BT.2020, S-Gamut/S-Gamut3 and S-Gamut3.cine colour space in full."

https://pro.sony/en_GB/products/broadca ... /bvm-hx310

It's harder to do than you think. Gamma shifts are solvable if you can color manage the signal and calibrate the display. Without that... it could look like anything.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 10, 2019 9:00 am

In a perfect world Marc, there would be monitors that cover full rec2020, and rec2020 would be new. But it's not.

Anyway, I saw an excellent TCL presentation on technologies to reach rec2020. I think hdtvtest.co.uk has a video on it, from early this year, or from last. Anyway, the industry is up to 90+% technology which only a few sets have. Hisense P9 (not the cheap one) last year, but only 8 bit panel with 10 bit dithering (this year's is the one to go for), TCL I think, and Phillips had a 40+ inch monitor, but again, 8 bit plus dithering. Sharp is another in 8k. So I bought a Samsung with much less colour coverage but 10 bit panel. Now, this year is 93%+. I'm not sure how close it gets to 97.x%. At that point it becomes more difficult again, which is why some proposed to bring the rec2020 spec down to it. These are technological figures, it doesn't mean that gamut is going to get from that technology through the screen. This gamut is not even close to what human vision can handle, but good enough for me, so I think people need to relax and enjoy the ride.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 10, 2019 11:04 am

This is yet another ''anomaly'. For yeras industry used 'outdated' Rec.709 gamut. Now they jumped to something big/theoretical. No one really thought about it? How we are going to display it? When they introduced Rec.2020 they should also properly set P3 as an option for gamut. Now P3 has been 'forced' by TV manufactures etc to be a new Rec.709 replacement, but there is no proper standard behind which could make it robust. I think I saw SMPTE to work on P3 as a standard for displays, but yet again it's all late.
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Re: Final Explanation of Gamma and Color Shift Problems

PostSun Nov 10, 2019 3:33 pm

It's aspirational, as was rec709 and P3 to some extent in monitors, as something display companies strive to meet over time (not really). The HDTV colour space was the backwards colour space based on what display technology could already do, but was holding back the industry. The issue is, companies want to sell cheap technology as high end technology, and drag their feet in order to draw more money out over time. So, even Samsung offered less rec2020 colour gamut this year than last, as I suspect they were planning to line up a new super series of models that needed to look a lot better, which hasn't eventuated (thanks).

Like with previous colour spacrs based on something real and we'll thought out, as long as you fit within the colour space and correctly map to other colour and display spaces, you are fine. But with companies with an eye on the past as the present, that would be an issue. Backwards is about making content backwards compatible rather than forwards.

Now, rec2020 nearly maps to the painters pallet, which represents most of the natural colour you see in nature and a bit more. Human vision can see more than that though. So, there is practicality behind it to some extent.

Now, projectors are claiming to match or closely match rec2020. Which might be the light source rather than what gets through the optical path and off a screen. But, yes, laser projection should get well beyond rec2020. If you go to the professional electronics engineering mags, you can see references to what's happening. Which are good places to get some reporting on expert analysis of what is happening. We here are mostly hair dressers compared to hair scientists in this regard. I'd rather listen to the hair scientists too rather than my opinionated 'expert' hair dresser.
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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 11, 2019 11:00 pm

Dmitry, I just wanted to thank you for this post. I've been trying to figure this problem out for years, bought a new iMac hoping that would fix it, little did I know it came with more problems with the P3. My main issue was having major gamma shifts when rendering from Resolve then uploading to Vimeo. My only work around was rendering ProRes 4444 and bringing that into Premiere, then rendering it down to 422 for upload. This was my only way to get my gamma corrected for upload, now I know Premiere was just was setting it back to Rec. 709.

I switched my Resolve Timeline gamma to Rec.709 and now I can upload straight to Vimeo exactly as I've graded it. I've emailed Blackmagic about this problem and all I kept receiving was that individual color management is too complicated. Thank you so much for sharing this, really appreciate it
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 12, 2019 12:15 am

Stuff, one of the things that should be simplest and is very important, is too complicated? Has anybody suggested to resolve, they should make workarounds to produce a set of delivery which covers most things. They can then put that in program help and have a button for each set to auto setup delivery, which the operator can then change if they wish. I can see how this stuff here is all way to complicated for new raw users.

At this stage, the harder alternative is to have individual selections for each player, and player edition functional change, you want to support, and fur it to kick out deliveries for each set the has a common delivery. Which is where industry comes in to do changes to standards and spend money making transform sets and code (as I suggested before) for players to use inside or outside the standards body, which fixes things long-term.

Do delivery platforms have the ability to sense the player used and auto deliver the highest supported version of a delivery that the player properly supports? Which I asked about before?
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 12, 2019 9:04 am

Wayne Steven wrote:Stuff, one of the things that should be simplest and is very important, is too complicated? Has anybody suggested to resolve, they should make workarounds to produce a set of delivery which covers most things. They can then put that in program help and have a button for each set to auto setup delivery, which the operator can then change if they wish. I can see how this stuff here is all way to complicated for new raw users.

Have I mentioned that this problem happens outside of Resolve and has nothing to do with Resolve? It's a color management issue made worse by uncalibrated displays. It doesn't help that many players will read the information differently from each other. In the specific case of QuickTime, Apple has not solved the problems very well.

I did mention checking everything out with SMPTE Color Bars, right? (Just checking.)
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 12, 2019 10:33 am

Marc, I read what you said. I had seperately been suggesting exploring ways to set up the content options so it is read in the most compatible way for a wide range of players and their faults, to reduce the deviation the most. That's Resolve territory. We might not be able to do much about screens without a standard to sense them and customise the footage, but we can at least get players to match up as much as practically possible.
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 12, 2019 11:05 am

JasonHan wrote:Dmitry, I just wanted to thank you for this post. I've been trying to figure this problem out for years, bought a new iMac hoping that would fix it, little did I know it came with more problems with the P3. My main issue was having major gamma shifts when rendering from Resolve then uploading to Vimeo. My only work around was rendering ProRes 4444 and bringing that into Premiere, then rendering it down to 422 for upload. This was my only way to get my gamma corrected for upload, now I know Premiere was just was setting it back to Rec. 709.

I switched my Resolve Timeline gamma to Rec.709 and now I can upload straight to Vimeo exactly as I've graded it. I've emailed Blackmagic about this problem and all I kept receiving was that individual color management is too complicated. Thank you so much for sharing this, really appreciate it


Formally It is not a Resolve problem, because as you can see you can adjust things in Resolve whatever you like. It is just global complicated situation when too many difefrent options are available instead one single solid unified specification between all systems.
P.S. First post was updated with some info from resent posts.

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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 12, 2019 9:08 pm

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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Nov 13, 2019 6:30 am

Dmitry Shijan wrote:Formally It is not a Resolve problem, because as you can see you can adjust things in Resolve whatever you like. It is just global complicated situation when too many different options are available instead one single solid unified specification between all systems.

That is correct. It's more of a player/interpretation, so it doesn't really help at solving the issue of gamma and color shift problems (as said in the first message). Blaming any of this on Resolve or BMD is unreasonable, since the problem existed long before Blackmagic took over Resolve, and in fact has been part of the color correction process for decades.

But the moment you provide color bars in the file, at least whoever receives it can check and say, "oh! We're way off and need to adjust this!" But without that, they have no way of knowing if they're bright, dark, low chroma, high chroma, 2.2 gamma, 2.4 gamma, whatever it is. SMPTE Color Bars will at least give people the ability to check, assuming the person on the other end cares enough to check.

If the material is going on a public player like YouTube, be aware that (again) the end result will change depending on what OS they use and what browser they use, as well as their display... which is probably terrible. No amount of color management can stop that, but at least you know when it got there, it was right. After that... who knows?
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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Nov 13, 2019 6:30 pm

We can presume that, but YouTube is not the only delivery platform. But it's about being part of the solution, as a product quality service. Same as other things, it's about what one can do
towards customer service, which is how industry matures forwards. I agree with the colour bars too Marc.
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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 18, 2019 9:48 pm

Dmitry Shijan wrote:If someone want to test on wide gamut Apple displays, here are gamma Rec.709 and Display P3 profiles with gamma 1.961 generated in DisplayCAL Synthetic ICC tool. They are v2 ICC profiles so they are more compatible with software that can not support more modern v4 ICC profiles:


Sorry for my confusion...
Are these ICC profiles made to A) use the iMac display as WYSIWYG reference monitor for grading, or B) to only compensate the gamma shift in QuickTime Player?
If A) then what about the ICC profile, that DisplayCAL created with my i1Display Pro?

Thanks in advance!
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 19, 2019 4:52 pm

Zweistein, those ICC profiles with gamma 1.961 are for test purposes only to proof that macOS video color management reads 1.961 gamma. You probably don't need to use them in normal color grading situations until you need to do some specific tests.

As a better quick fix for P3 displays you can use monitoring correction LUTs made by Cosmin Hodiș-Mîndraș. See details in this post viewtopic.php?f=21&t=101253&start=50#p564992
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 19, 2019 6:02 pm

Dmitry Shijan wrote:Formally It is not a Resolve problem, because as you can see you can adjust things in Resolve whatever you like. It is just global complicated situation when too many difefrent options are available instead one single solid unified specification between all systems.
P.S. First post was updated with some info from resent posts.


Exactly!

I have producers asking me constantly how to solve this. My answer? Get off Quicktime.
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 19, 2019 6:27 pm

And you think it's that easy?
As I said before- QT X is actually most correct here when files are flagged properly.
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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Nov 20, 2019 3:26 am

Why you talking about quicktime? It's much wider than that. Agreeing with a non answer (ontop of the correct answer given) doesn't really help with the question of ways to temporarily get footage to closely match on as many of the important systems as possible.
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Re: Final Explanation of Gamma and Color Shift Problems

PostWed Nov 20, 2019 11:04 am

Dmitry Shijan wrote:Zweistein, those ICC profiles with gamma 1.961 are for test purposes only to proof that macOS video color management reads 1.961 gamma. You probably don't need to use them in normal color grading situations until you need to do some specific tests.

As a better quick fix for P3 displays you can use monitoring correction LUTs made by Cosmin Hodiș-Mîndraș. See details in this post viewtopic.php?f=21&t=101253&start=50#p564992


I see. Thank you!
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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 25, 2019 4:06 am

Wayne Steven wrote:Agreeing with a non answer (on top of the correct answer given) doesn't really help with the question of ways to temporarily get footage to closely match on as many of the important systems as possible.

I don't think it's possible in the real world. I think you can get it in the ballpark, but so much depends on the display's calibration, it's a crap shoot.

One interesting experiment: render a file. Take that file and upload it to YouTube. Using a downloading utility (like Downie), download the YouTube file. Now take that file and bring it into Resolve, and compare it to the original session. What do you see?

Generally, when I do this the differences are negligible. Given that, the culprits are now the actual playback engines being used, plus operating systems and browsers. But I think the displays themselves have the greatest effect, particularly once they're calibrated (or close to it).
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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 25, 2019 4:28 pm

Thanks Marc. I'm not concerned about the displays themselves, as that's generally out of our reach and up to the owner. But, I am concerned about getting the rendering engines to recognise things similarly. It doesn't have to be perfect, users generally probably would not recognise the difference. Dmitry gave a part answer above. I think it was HGL HDR through rec2020, or was that BT2100, gave tighter control, or something. Given software upgrades to players and rendering engines, that might be part of a solution. YouTube is YouTube tricks, but you aren't finding that too bad
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Re: Final Explanation of Gamma and Color Shift Problems

PostMon Nov 25, 2019 4:38 pm

An interesting thing. Didn't I read a Hybrid form of HLG where they can set the parameters per frame using the work of technics or somebody?
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Re: Final Explanation of Gamma and Color Shift Problems

PostTue Nov 26, 2019 12:52 am

Wayne Steven wrote:Given software upgrades to players and rendering engines, that might be part of a solution. YouTube is YouTube tricks, but you aren't finding that too bad

We only deal with SDR on the web, in the real world. I think HDR for the web is imaginary at this point. They can't even get SDR right at this point. It's kind of like people worrying about 8K delivery, when no website of which I'm aware can reliably handle low-compression HD.
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