Quicktime Gamma Shift Bug - What is it and how to "combat" it?
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- čas přidán 4. 01. 2024
- As creative professionals, most of us have likely run into this problem, and it is tricky to pin down - why isn't the color of my video matching 1:1 between my export and my editing timeline? What the heck is going on? Is QuickTime somehow at fault? Is it my operating system? Or is it something else?
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Have you been affected by this Gamma shift bug when exporting video?
Yes in resolve.
Easier to handle on resolve.
Great explanation. I used to battle with this all the time. No longer using quicktime, VLC is the way to go.
Hey@@MatixLA ! Be careful with VLC because it is not a color managed application. If you are using VLC in MacOS on a P3 display and expect to be reviewing your export for Rec709 colors, you will be seeing the wrong interpretation of Rec709 because it hasn't been converted from your Display's Native P3 color gamut. I hope this clears some things up and if you have any follow up questions feel free to reply!
Something I'm still a little unclear on: I have a reference display going through a Blackmagic Decklink. I grade in Resolve for Rec709 and then bring the files back into Premiere for final export (audio layback, slating, etc). Will bringing the graded files back into Premiere result in a color shift if I don't do the Lumetri thing mentioned in the video? Or is just how the exports appear when viewing via QuickTime, VLC, et al? Thanks!
I think this is the closest explanation to the problem but a couple of minor details in the problem should be pointed out. The original gamma that led people into calling it the quicktime gamma shift was a similar problem from our history that the original Apple displays before the was any HP/Microsoft coalition coming the the sRGB standard of gamma 2.2 ( approx ) Apple display were using gamma 1.8 - so the difference was way off back then.
Now coming into the problems we have now - Color Sync is the problem but not exactly as was explained ( but really close ). The math is assumed By Apple and applied on the fly to a color managed workflow as described but the value of 1.96 is what Apple assumes is the encoding from linear to non linear ( camera gamma ) but in almost all devices and cameras ( the rest of the world ) the gamma encoding math is assumed to be 2.2 - This is where the difference and math problem arises.
Typical math with 2.2
Suppose we have a camera that uses a gamma value of 2.2 for encoding (γ = 2.2).
1. Gamma Encoding (Camera):
• Let's say the camera captures a pixel with an original linear light value of V_in = 0.5.
• The gamma encoding operation is: V_out = V_in^γ = 0.5^2.2 ≈ 0.2176
• So, the camera encodes this pixel with a value of approximately 0.2176.
Then in the display gamma decoding ( for your monitor )
• Now, we want to correctly display this encoded pixel value on a monitor. We need to perform the inverse operation.
• The decoding equation is: V_out = V_in^(1/γ) = 0.2176^(1/2.2) ≈ 0.4999
The monitor will display this pixel with a value of approximately 0.4999 ( which is the .5 linear we started with )
This process ensures that the image is correctly displayed, compensating for the gamma encoding applied by the camera. This correction is crucial for the image to appear visually accurate to human observers.
Now if Apple uses gamma 1.96 for the gamma encoding to a file as it does on the fly whenever a file is going through Apple colorsync.
The display encoding math will return a different result - the V_out = V_in^(1/γ) = 0.2176^(1/2.2) ≈ 0.4999
in this equation using 2.2 we get the 0.2176 but using 1.96 we get 0.2570^ (1/2.2 ) = 0.5392
So it appears brighter at the display function.
The compensation for that difference is calculated in the Davinci Resolve Resolve band-aid of rec709-a and Adobes compensation LUT.
And as explained both software have the ability to let you grade by seeing the colorsync version in it's source monitor.
What wasn't discussed in the video is the other problem with colorsync using NCLC tags for viewing video files. And that for some unknown reason ( can't find out why ) NCLC tags have no actual definition for gamma 2.4 even with it being the standard for broadcast gamma as in the BT1886 rec709.
This part was a bigger problem in Resolve because using the output of rec709 gamma 2.4 the file would be tagged 1-2-1 which Applesync reads a typical tagging of a rec709 gamma 2.4 file )( 1-2-1 ) as the following:
Color Primary - "ITU-R BT.709"
Transfer Function - "Unspecified"
Color Matrix - "BT709"
So when the display transfer function is unspecified the inverse they apply is an inverse of the same badly assumed camera display function of 1.96.
So it's even worse.
Premiere didn't have this problem because it tagged rec709 as 1-1-1 and if you use the Resolve rec709-a it also retags the file to 1-1-1.
I have to hand it to you guys though - your whole explanation is the closest I have seen to date. Great job explaining Kevin
Yes! This is all correct and I really appreciate your words, Jim. I wanted to play a careful dance of giving viewers just enough information without getting too overly technical. Your comment is 100% spot on and anyone coming to this video should read what you just posted.
Thanks for this Jim!
Thanks for the great explanation Jim, I've been looking for a long time to figure out "how accurate can a macbook pro monitor be?" See you at Grade School :)
I don't want to dive down a whole other rabbit hole, but the Macbook Pro display has multiple other profiles, does switching those profiles to something like P3-ST 2084 change the calculations, and would they then match better? I am trying to work out the pipeline here, and if Davinci uses the MacOS profile, and the MacOS profile is set to P3-ST 2084, and I set that as my output in Davinci, would the video look the same in quicktime on my screen, and in the monitor in Davinci?
One other thing I was curious about is that ColorSync uses profiles, would it not be possible to just use a different profile for Rec709? Replace the default with a custom one that uses 2.2 or 2.4? Of course this will ensure your display matches non-apple displays, it won't fix the issue in general, but I like digging around in file systems and trying custom stuff :)
@@MaximoJoshua Changing the display profile set in preferences will change the math. For instance you can set it to their BT1886 profile which does handle Rec709 correctly as per filmmakers standards. The issue is that it then breaks all other elements of the OS and of course the philosophical debate opens which is that this isn't the default experience for Mac users, so you are the only one previewing the content in that way. Even though it's the right way, it's a whole can of worms when you ask your clients to review color passes first by switching the settings on their computers ;).
Despite this, it is fun to play around with the settings and learn how it all works under the hood!
@@kevin.stiller yeah, exactly, it comes down to whether i want it to look correct on macs, or on everything else...hence the goldilocks solution. I just want to try and minimize the error for all displays. I did see an interesting article, which also kind of speaks to Jim's point, which was that Daria Fissoun I believe recommended to set the output to Rec709/Gamma 2.4, but in export settings, under advanced, change it to Rec709/Rec709-A (I think that would fix the tags).
I am kind of just hoping everyone makes the jump to HDR. As more content gets graded for Rec2100 or Rec2084, wouldn't this problem just kind of go away on its own? I have been experimenting with just exporting HDR for youtube, which they will convert to SDR. Its not perfect, because I don't think most HDR systems use P3, they should be using Rec2020. So the mac display still doesn't exactly measure up, even though I think ColorSync will at least convert accurately between p3 and Rec2020 as well as between HLG or PQ and whatever the mac display uses
Great explanation!
Thank you both for this! Kevin you rule! Thanks for this great video
You are heroes, very technical heroes
Great job breaking this down. This has been one of the top questions for new video editors for so long. I remember my early days struggling with this.
Thank you so much Kevin! Yes, it's crazy how long this has been around for.
Finally! Thank you so much.
Thanks for watching, David!
I wish Apple would update the gamma setting for Rec709 to assume BT.1886.
Thank you guys !! this truly helped me !!
OMG finally an explanation!! no more QT gamma correction when exporting from Premiere!
Correct!!
what's the fix? This video is so long
@@aristideregnier4883 the issue Adobe Premiere users have when exporting on Mac OS is the render will have a strange contrast/gamma shift to appear more desaturated. this person explains what causes and what settings you could adjust to avoid it. for me, it has been a mystery that is now solved. 🙌🏽
+1 on linking to the fix, I can't even tell if it's coming 10 minutes in
THANK YOU - After years I do now understand and can better deal with it !! - GREAT !
So glad you found this helpful Stephansilwester!
Thank you
Well, now I'm glad youtube repeated repeatedly notified me about this video. Google knows dam well how many times I've tried to research color space glitches like this. I'll be basing on 2.4, not 2.2 "middle ground" as I'd rather imagine seen by someone as flater and unsaturated then as oversaturated with too much contrast.
Thanks for this!
I can't say thank you enough for this... I have been haunted by this for years.
Very glad to hear its helpful for you. It's haunted me as well!
Great job Kevin this is totaly a game changing video. Apple always have to do it the other way and still everybody is buying it i can not understand
Thank you so much Antoninolongo!! So glad its helped you.
On the other hand, if you are using Windows and say, Davinci Resolve, and that is not a small section of the video making population, and you grade a video till it looks good on your colour critical NEC monitor, but then upload it to Vimeo, or transfer it to your iPhone, the result looks desaturated and lacking contrast. Mac users are locked entirely into their own ecosystem, grading on Mac, viewing on Mac, iPhone, iPad, and most likely see no problem. But editing on Windows, viewing on iOS, frustrating to say the least.
You can also make sure you are monitoring in the right color space if you go to display settings and change your display to view in HDTV Video (BT.709-BT.1886). Make sure your pipeline is still correct but this will add another layer of security that it is working correctly.
This may only work well with the pro lineup but it is possible.
This is true! Confirmed working on the XDR displays
so if I set to HDTV, I dont have to select 1.96 gamma in premiere lumetri settings? Sorry just trying to figure this out.
@@Emilioh888 From what he said in the video, it would be gamma 2.4 because it is BT.1886. So you just have to chose which one you want.
AMEN :)
I think Apple has kind of left Rec.709, and moving on to 2020 and 2100, HDR, HLG etc. What are you thoughts on that?
I suspect you are probably correct. It would be nice if they could pay attention to this aspect a little more, but knowing that they continue to try and push the envelope with their hardware, this upwards path only makes sense!
Very good explaination. Thank you for putting this together. I got one questions. HDR on or off on a HDR-display?
It's difficult for me to answer that because I am not sure what you are using the HDR display for!
@@kevin.stiller I got two LG 4K HDR10bit monitors on my Mac Studio, byt no real reference monitor yet. Trying to get best DaVinci experience and color accuracy out of what I got. Both monitors calibrated using Datacolor Spyder X.
So basically Apple is behaving like a baby.
So I have a 2021 M1 Max MacBook and the way I edit with Premiere is one large 27in display as my primary and the macbook display right next to it as the fullscreen preview display via the mercury transmit thing...if i do what you suggest and change my viewer gamma to 2.2...the macbook display does not change...and what seems to match best is 2.4 like it was originally...so its kind of confusing that the macbook monitor will always show 2.4 essentially even though macos will always make it 1.96....should i just fullscreen the program monitor on my macbook display instead?
@kevin.stiller what are your thoughts on the Adobe qt gamma lut? Also, since iPhones are dci-p3, I assume that grading using the standard MacBook XDR profile would be the best option? Or better to just set the monitor profile to to rec 709 and continue that way? Thank you
I have been struggling to fix this exact issue with my client as we always had different views every time I threw color grading preview via Google Drive to them. They always said the image is too bright and the skin color is a little bit weird, while everything is look normal to me on my MacBook Pro M1 Max. I began to lose my mind and we have no idea which version of it will be displayed when exported as DCP and screened via the theatre's Doremi server projectors...
Yep!!! Have had this exact same scenario happen to me more times than I can count
Why does this not happen in FCPx?
Fantastic video! I currently don't have a reference monitor. For someone working in After Effects, how would you go about solving this issue?
Do you see the "8 bpc" or "16 bpc" button under your project window? Click that and tab over to "color". Enable "adobe color managed".
Under color settings set your working color space to Rec709 Gamma 2.4. Then, use after effects in a dim surround environment. Not total blackout, but dim.
Just to be clear? For the best (widest-compatibility) solution for resolve would be
1. enabling the use Mac display color profiles for viewers
2. Setting timeline color space to 2.2 or 2.4 or scene
3. Setting output colorspace to 2.2
Correct?
If you are on a MacOS device, enable use mac display color profiles for viewers
close and reopen resolve
Timeline color space should match your source material or intermediate color space
Output color space to Rec709 Gamma 2.4
Put yourself in a dim environment
Export as per traditional Rec709 spec.
All good to go!
Or you can do Gamma 2.2 as the output color space for your viewer if you are in an area with moderate surround lighting such as an office.
Thanks for this explanation ! Any problem on FCPX ?
By default, FCPX will show you correct Rec709 colors because it has color management enabled "out of the box". However, it is decoded based on gamma 1.96, so it shows you what quicktime, preview, chrome, etc will show you. There will be a gamma shift everywhere else. Android, windows, etc.
Thank you for this excellent video., it's is a very interesting insight.
But the thing I often hear is that the answer to the problem is having a reference monitor. I have one, it's calibrated for BT1886 rec709, but when I export my work in Resolve the result is still being reproduced 'different' when I watch it in a color managed app on a Mac with a Mac P3 display than on my reference monitor.
The issue of Color Sync interpreting rec 709 differently than my reference monitor is still there. So what am I missing here? In what aspect is it the answer to the problem?
The answer IS to have a reference display
MacOS will always interpret Rec709 differently. This video is purely meant to be an educational tool to inform folks about it.
T H A N K Y O U
It's been years of pure pain and frustration
T H A N K Y O U
Thank you very much for this ! However, when i change my settings like you propose on davinci, my image becomes way darker, and extremely contrasty (quite the opposite from what you say...?). Also, when i change the output color space, it does not do anything. i can choose any color space, no difference... is there something wrong ? please help :)
i actually found out that it was my timeline color space which was set to 2.4. but aftr a test, i now have the issue that with quicktime, or the finder player, the video is EXTREMELY washed out (way more than the issue you are describing), and under VLC it is prfect. Can somoene help me ? thanks !
@kevin.stiller I have a question for you still. I'm one of the lucky ones who DOES have a reference monitor. However this problem still plagues me because I will grade with clients who love a look in a controlled environment only to panic email me the next day that it looks "washed out" on their iPhone etc. Any thoughts on how to handle this annoying (and recurring) problem? Especially if delivering for web and NOT broadcast? 709-a / Gamma 2.2? What's the latest and greatest?
There actually is no solution currently, as MacOS, iOS and PCs will not play a Rec.709 (1-1-1) file the same way, and CZcams and Vimeo strip out the Colorsynch tags if you deliver anything else. If you have a Rec.709 external SDI reference monitor, the best you can do is insist that your client watches the file on an iPad (preferably in reference mode, but at least with truetone and nightshift turned off, and in a sensible environment, but good luck getting your client to follow those instructions! Some productions actually send their clients correctly set up iPads for this purpose. As for your delivery you could target Rec.709 2.4 and have it look great on iOS, or sRGB and have it look good on a PC, or Rec.709-A and have it look good on MacOS, or something in between, but frustratingly there’s no way to deliver a file that looks right everywhere. Working in HDR may help, but this isn’t an ideal solution as almost no one is watching in HDR, so they will be looking at a conversion of some kind.
Is After Effects color managed?
Semi newbie here: Does the Premiere QT Gamma export LUT fix fit in somewhere to the topic being discussed here?
Solution at 17:30
So what happens if we switch the display color mode to 709 1886, wouldn't that fix the issue?
Good question !
What about FINAL CUT ?
Final Cut works fine no twiddling required
is this true for all monitors, or only for apple ones? For example, what about a mac studio with third part display? Because with this setup I see no difference for the same video un mac and pc in VLC players and da vinci viewers, but enabling mac display color profile for viewers in da vinci the only corresponding image result da vinci and quicktime for ONLY rec709A export. For broadcast delivery could be a good idea calibrating a monitor in rec 709 gamma 2.4 profile to avoid problem?
Very easy to understand this way! The only thing i'm still not really sure about is the assumption that grading in 2.2 is "safe". Is the iphone doing the same conversion with chrome/safari/youtube? because if so, there are a so many people (at least in my surroundings) that are viewing my exported videos on apple devices. which means a horrible conversion for the majority. I might consider to just cut my losses and grade in rec709 1.96. or maybe even p3.
In my experience, iOS does NOT decode rec709 with gamma 1.96. It uses 2.2. iOS and MacOS do not match one another in that regard. However I have heard stories of folks with the iPhone 15s having a different experience, so take what I am saying with a grain of salt and do your own testing!
Am still using gamma 2.2 for grades and works fine on my apple devices as well as android and PC. I actually prefer the looks after grading when displayed on my apple devices even though I use windows pc for all of my works.
So the real problem with this shift is color correcting and grading based on a faux color shift, then getting a surprise later when things come out too dark and saturated. Am I understanding this correctly? My workflow is very simple compared to a Hollywood-style shop. Usually RED log clips, color and edit. So I need to ensure I'm at 2.2 or 2.4 gamma before the color phase or I will color based on the QT issue.
Nice Video!!!! But where are the links?
Links can be found here: www.cined.com/quicktime-gamma-shift-bug-what-is-it-and-how-to-combat-it/ Thank you!
Another note, my samsung galaxy phone has a "video enhance" feature.. it looks like it just boosts the gama and saturation, on a display that already pushes its limits. I keep it off cause it blows out bright saturated colors, resulting in a loss of detail. Some people like that look, and good for them, they have the option to turn it on, I'm just thankful it isn't baked in. Apple could one over Android by updating to assume 2.4 as default then give "video enhance" options to either revert back to legacy mode, keep it at the new standard, or push the saturation and contrast.
I can set my internal display colour profile to Rec. ITU-R BT-709-5 even on a simple MacBook Air m2. Doesn't this solve the issue? Why should anyone grade Rec709 on a P3 profile?
Commenting to follow
iPhones and high end androids are using p3 colour space, so I guess grade in p3 so that it’s most compatible with everyone? Also if you grade in 709 colour profile and send to a client on a macbook set to default p3, it won’t look right I assume. Theoretically you are right but it would take everyone to have a monitor set to rec 709. I hope that makes sense, I am trying to figure this out as well. I usually use the Adobe qt compensation lut but I not happy with the results, it’s too dark, even when seen on an new iPhone 14 which has high brightness.
@@Emilioh888 if someone is grading (professionally) he should be able to set his monitor to the corresponding profile.
So only the gamma Bt.1886 (wich is something close to the gamma 2.2 on LCD's and closer to 2.4 on OLED's from what i found out) is still not available in this editing programs. Haha
Good approach, but it could have been shorter!
Still using gamma 2.2 in grades and am fine with it.
I can tell you why this is happenning in Davinci Resolve, I know the reason well - it is because
1/ Davinci is shipped NOT COLOR MANAGED by default on Mac platform (you have to configure settings for color management to start working)
2 Davinci refuses to mention this info in their famous 4000+ pages manual. NO instructions given there at all on how to setup Davinci to work with Mac color management on a GUI display.
So if you setup Davinci properly, there will be zero issues with colors not matching on export.
Unbelievable ...
The export looks washed-out but on the other hand video on Netflix (Safari) looks too dark. On a M1 MacBook the default Display profile is LCD. Switching to P3 shows how much of the darker picture information has been lost. Seems to be the same bug?
And FINAL CUT?
FCPX will show you correct Rec709 colors because it has color management enabled by default. However, it is decoded as gamma 1.96, so it shows you what quicktime, preview, chrome, etc will show you. However there will be a gamma shift everywhere else. Android, windows, etc.
It’s the premiere viewer that’s the problem. Resolve doesn’t have this issue. If you render footage from resolve, and bring it into premiere, and render it out of premiere, it will look identical to what you rendered out of resolve. And that will look right on web, phone, TV, computer, etc. it’s premiere that is not showing an accurate image.
Resolve has the exact same issue. Just tested it out again today. Anything you export from Resolve will look more washed out if you watch in QuickTime, but if you watch in in VLC it will look exactly as it does in the editor
too long of a video, what's the fix? Gamma what?
Gamma 2.2 is standard for all devices. But you need 'personal' gamma for your player to match it's particurity.
Try use VLC or some other players.
Gamma 2.4 is WRONG for average consumer because PC displays and consumer TV sets are set to gamma 2.2. That why only PROs who edit for CINEMA and TV broadcast use gamma 2.4 - IT IS NOT a standard for consumer displays
THe video is exceedingly diluted and over-complicated. Simple facts are - . THere is no quicktime bug in current Mac OS, and NEVER WAS! Indeed long time ago Quicktime on mac displayed videos with a slightly brighter gamma for more pleasing presentation on the average mac monitor of those days. Thats ancient history now and they stopped doing it 20 years ago! Now the issues described in this video are 100% related to video editing software settings. E.g. Davinci IS NOT COLOR MANAGED on Mac platform BY DEFAULT! You need to dial in proper settngs for it to show proper colors on a Mac GUI display. If you set up Davinci Properly you will have perfect 100% match on export, upload to CZcams, etc. He gave himself away when demonstating the bug he only mentioned Premier and Davinci - 3rd party apps. Apple’s own Final Cut works fine out of the box, not requiring any twiddling.
@sunlit777 - what are the proper settings for Davinci on a Mac? Thanks
@@AA-uu8ox czcams.com/video/t1NdumUmp7I/video.html
ahh yes. classic apple bs. Like their bad macbooks wich have the same hardware issues over 4 generations and the dont want to fix it. ah yes...