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Dimitris Stasinos

Standalone video players & colour reproduction

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Hi guys. I don't know if this has been discussed before but i didn't find a topic about this. I am working with FCPX on a late 2015 27 iMac and i am seeing a red shift while playing back my videos on VLC. I am seeing the exact same gamut with FCPX when using Quicktime. Now, with After Effects i see the exact opposite phenomenon. Videos that are exported from After Effects play fine on VLC, while Quicktime introduces a drastic desaturation on the red channel. After calibrating my monitor using iDisplay Pro last year, this is getting kinda tricky, don't knowing which application to trust. Is there a standalone player that you trust more than these two? Any ideas why this is happening?

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EOSHD Pro Color for Sony cameras EOSHD Pro LOG for Sony CamerasEOSHD C-LOG and Film Profiles for All Canon DSLRs

I'm no expert, but I have been researching color calibration as well.

If you are using a monitor plugged into your gpu, calibration happens using an icc profile, which tells the software color shifts to compensate for the hardware inaccuracies. Unfortunately, icc profiles are implemented on an application level, which means some applications might use them, as some might not. So it may be the case that QuickTime uses the icc profile created by your idisplay pro, while vlc ignores it (or maybe vice versa). Most video editing software appears to ignore the icc profile.

however, just to make matters worse, the gamma table is implemented system wide. So you should theoretically have universally calibrated gamma, while the color is application specific.

As for which to trust, ive found that many picture editors, such as krita, or rawtherapee, let you manually specify an icc profile to use. Since I can be sure they use the calibration data, I trust them more than any of my video software. so after calibrating, I export a still frame, a open it in my image editors, and compare that to the video software to determine which is most accurate.

the best solution is of course to use a lut box or a monitor that supports luts, so that ALL color from your computer is calibrated, not just from certain applications. If that is not an option, make sure you are using the hardware rgb sliders on your monitor to get as close as possible durin calibration.

hope that helps, and if you find anything that contradicts what I said, let me know! Color calibration  appears to be a dark art, and I'm not sure I've got it all right.

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Thanks @KnightsFan! This is valuable info.

As far i know FCPX uses the icc profile, specified by the user. Actually i opened a project on FCPX and tried to change my icc profile. The GUI colors changed instantly but the image on the preview window of the editor took a 1 sec delay to adjust so i think this might be indicative. I guess that Quicktime also implements the icc profile because i can see no gamma shift there. 

But indeed, things start to get complicated with apps that don't implement the icc profiles, like Premiere and After Effects. So even if a grade seems fine on Adobe's GUI and even on a player like VLC, the proper reference is Quicktime which uses the icc profile, right? So if the image looks desaturated on Quicktime the solution is to make a custom lut for After Effects which pushes the gamma to higher values. Is this correct?

Scary stuff...:)

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If you have an Nvidia GPU, there's a setting for video color range that's also really confusing in that it affects some applications but not others:  16-235 or 0-255.  

And if you don't set it the right way video in some applications look weird.

 

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4 hours ago, Dimitris Stasinos said:

I guess that Quicktime also implements the icc profile because i can see no gamma shift there. 

Keep in mind that the VCGT (video card gamma table) is universal, while the icc profile is not. So you should have the correct gamma everywhere already.

4 hours ago, Dimitris Stasinos said:

So even if a grade seems fine on Adobe's GUI and even on a player like VLC, the proper reference is Quicktime which uses the icc profile, right?

Assuming Quicktime uses the calibrated ICC profile, yes, that is correct. (As a Windows user, I have no experience with Quicktime).

4 hours ago, Dimitris Stasinos said:

So if the image looks desaturated on Quicktime the solution is to make a custom lut for After Effects which pushes the gamma to higher values. Is this correct?

If an application such as Quicktime is verifiably correct, then yes, you will probably have to use a LUT to make your other software match. I would try to confirm Quicktime's accuracy using image editors, as they usually have better icc profile support than video applications (after all, icc profiles are used calibrate printers for printing photos). If 4-5 different photo editors all use the calibrated icc profile and match each other and quicktime, you can be reasonably certain those are all correct.

However, gamma should be correct already (if my understanding is correct... I'm still figuring this out!) so my suspicion is that it's a problem with actual colors, or with video vs. data levels, rather than a gamma problem. I don't know how color management works in AE.

 

Which software to you use for calibration? I use DisplayCAL. It has a lot of nice tools, like generating a LUT from the icc profile. The forums there seem like a good place to ask questions.

Final note: VLC absolutely SUCKS for color. Afaik, there is no way to use an icc profile, and even a simple thing like specifying 16-235 vs. 0-255 levels is unreliable. You can be reasonably certain that VLC's color is not accurate.

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I just calibrated my monitor again, but this time used DisplayCal as @KnightsFan suggested, instead of iProfiler. Same settings but totally different results. X-rite's app (iProfiler) gives a strange red shift. Many users have mentioned the same thing, so i can definitely confirm this.

As for After Effects, i forced the application to use my icc profile and the results where totally off. I tried the same thing with Premiere by exporting stills which i passed through a simple colorimetry process using Photoshop. I am sure i made a lot of mistakes and this was not a scientific test in any universe but i can say this with confidence: The color management in Adobe video apps on a mac doesn't work in harmony with Colorsync. Even if you force these apps to implement an icc profile you can't trust what you see.

KnightFan said that VLC's color is not accurate and i totally agree. But i was not expecting in any case that i would see the exact color management inside 2 widely used Adobe's apps.

I made a custom lut in Photoshop, then added that on an adjustment layer in AE and exported my files again. That was the quickest way to fix the color shift and it worked as a charm. I think...

Overall i think those are major issues and must be discussed more on the forums. It's funny cause we talk everyday about how disruptive a codec or a compression method could be and i just discovered that every single clip i have exported from AE has been rendered in a slightly shifted colorspace.

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On 10/13/2018 at 1:37 PM, Geoff CB said:

Media Player Classic gives the best results for me on PC. 

 

8 hours ago, ade towell said:

Me too

I checked out Media Player Classic Home Cinema (MPC-HC). It's an improvement over VLC, but it does not match my other color-managed applications (yet!). Would you guys mind sharing your settings or any insights? Currently, I have found:

A) Davinci resolve, Krita, Rawtherapee, and GIMP all look identical, and all are manually set to use my calibrated icc profile. In the case of Resolve, this includes generating a 3D LUT from the icc profile using DisplayCAL, as per the tutorial here. (Though I am using sRGB instead of Rec709).

B) MPC-HC looks identical to the default Windows Picture and Photo Viewer, but appears to have slightly more contrast than the programs listed in A), or maybe just a slightly lower black level. I adjusted every setting I could find, but could only get worse results, not better. Reading through Wikipedia, I came across this:

Quote

Unlike most other RGB color spaces, the sRGB gamma cannot be expressed as a single numerical value. The overall gamma is approximately 2.2, consisting of a linear (gamma 1.0) section near black, and a non-linear section elsewhere involving a 2.4 exponent and a gamma (slope of log output versus log input) changing from 1.0 through about 2.3. The purpose of the linear section is so the curve does not have an infinite slope at zero, which could cause numerical problems.

AND I notice that in the color management section of MPC-HC, you can choose between Gamma 2.2, 2.35, and 2.4. So perhaps MPC-HC is actually using a single gamma value? That would explain why it looks just BARELY off from the A) programs.

C) VLC is on its own planet. Changing renderers will change the colors around, but they don't explain what is actually happening so it's anyone's guess which settings are most accurate.

 

1 hour ago, Dimitris Stasinos said:

Overall i think those are major issues and must be discussed more on the forums. It's funny cause we talk everyday about how disruptive a codec or a compression method could be and i just discovered that every single clip i have exported from AE has been rendered in a slightly shifted colorspace.

I couldn't agree more. Every day, lots of people here on EOSHD discuss the color science of various cameras. I'm assuming they are all viewing on calibrated monitors? If so, I hope they will chime in and help us out!

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Dimitris, maybe the problem is the codec you are using to export the files.

Which codec do you use? 

After effects has color management. Premiere doesn't. You have to create a lut for it.

On After can go to Project Settings -> Color Settings and choose the color space you want to work.

I have found that Rec 709 Gamma 2.4 has inconsistencies when exporting ProRes files.

For ProRes export, working in sRGB 2.1 colour space gives me the most accurate results.

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Just did a quick test on Davinci also.

The way I get the exported file (ProRes) to look exactly the same with what I see inside Davinci is this:

1.Turn off "Use Mac Display Color Profiles for Viewers

2. Instead, convert your monitors' icc profile to .cube and use it as a 3D Video Monitor LUT

3. Use sRGB for Timeline Color Space

4. Export ProRes

I'm sure that this is not the correct way to do it, but this is a workflow that works for me.

01.png

02.png

03.png

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Thanks for your input @Stathman

Indeed i used ProRes 422 for my tests and this where the color shift pops up.

Choosing my icc profile in project settings didn't work in first place (i was getting strange results) but i just tried the sRGB 2.1 colorspace

you mentioned and i can say it's the closest thing i can get to the rendered file. Thanks for that man!

This is legit workaround and more reliable than using my own lut.

As for Resolve, the most common solution is what KnightsFan suggested. Making a custom LUT through DisplayCal. 

 

 

 

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After some more tests on after effects I have found that this settings gives me the most accurate results:

1. Enable "Use Display Color Management"

2. Prepare your work in Rec.790 Gamma 2.4 color space

3. Just before rendering switch the working space to sRGB 2.1

4. The exported ProRes file will look almost identical to the preview you get on Rec709 working space. Just with a negligible exposure shift.

On.png

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