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Rec. 709 Gamma 2.4 vs HDTV (Rec. 709)

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Filip Stillerska
Rec. 709 Gamma 2.4 vs HDTV (Rec. 709)
on Apr 5, 2018 at 5:18:31 pm

What's the difference between Rec. 709 Gamma 2.4 and HDTV (Rec. 709) in AE? Which one should I use for advanced VFX when working in linear color space? Also, which one does Premiere Pro use?



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Neil Hammers
Re: Rec. 709 Gamma 2.4 vs HDTV (Rec. 709)
on Apr 6, 2018 at 12:45:26 am

Can't comment on the gammas and Premiere, however you probably aim for the colorspace standard that contains most of the info.
https://www.usa.canon.com/internet/wcm/connect/us/13df3b56-1aa0-4ee3-aca6-e...
This might help you to decide which colorspace to stick to. On other hand, going for ACES can be an overkill if you are not going to print on film or do some really advanced screening.
Make sure you not only set the desired working colorspace for the project and at least 16 bpc, Trillions_of_Colors in Render_output module and the codec that supports at least 10-bit encoding.. could be Quicktime with Avid DNxHR at it's top quality.

Nh


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Filip Stillerska
Re: Rec. 709 Gamma 2.4 vs HDTV (Rec. 709)
on Apr 6, 2018 at 11:35:50 am

Yes, I definitely wanna stick to Rec. 709 - no doubt about that. I'm just trying to figure out the difference between Rec. 709 Gamma 2.4 and HDTV (Rec. 709)


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Filip Stillerska
Re: Rec. 709 Gamma 2.4 vs HDTV (Rec. 709)
on Apr 6, 2018 at 11:37:36 am

Also, I know that Premiere uses Rec. 709.


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Dave LaRonde
Re: Rec. 709 Gamma 2.4 vs HDTV (Rec. 709)
on Apr 6, 2018 at 3:20:07 pm

A couple of test exports from AE using the same clip ought to settle the issue.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Pierre Jasmin
Re: Rec. 709 Gamma 2.4 vs HDTV (Rec. 709)
on Apr 8, 2018 at 5:08:19 am

Gamma 2.4 versus Gamma 2.2? - (rec 709 gamma 2.2 = sRGB, and gamma 2.4 can be a delivery requirement of some "tv/broadcast" -- not sure how to call these in internet days) - primarly a difference near black

Pierre



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Pierre Jasmin
Re: Rec. 709 Gamma 2.4 vs HDTV (Rec. 709)
on Apr 13, 2018 at 9:53:50 pm

Sorry I pressed report post instead of reply - the question was which gamma Premiere uses - I think they are now at gamma 2.4 rec 709. The image won't look exactly like elsewhere on your computer if your computer is set (as should be for normal usage) to sRGB

Pierre



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Andrew Somers
Re: Rec. 709 Gamma 2.4 vs HDTV (Rec. 709)
on Jun 21, 2018 at 2:55:41 am
Last Edited By Andrew Somers on Jun 21, 2018 at 3:32:05 am

"What's the difference between Rec. 709 Gamma 2.4 and HDTV (Rec. 709) in AE? Which one should I use for advanced VFX when working in linear color space? "

You can use any of those or even sRGB in a linearized workspace, as the gamma in the profile is not used, only the color coordinates of the primaries and white point.

When you are working in LINEARIZED space, your gamma is 1.0

sRGB and Rec709 use the same primary coordinates, so there is no difference between them when linearizing your workspace.

None of those profiles should be used for output though. When you are converting from linearized space to render out to a Rec709 video, you want to use the correct gamma for video files, and the gamma of such a profile is closer to 1.9-2.0, and not 2.4.

The "HDTV (Rec709).icc" profile uses a 2.2 gamma curve (and appears no different than sRGB) with no offset as is specified in the actual ITU-R. It does not have the proper Rec709 gamma.

The profile I am recommending is: Rec709-elle-V4-rec709.icc

Downloadable here:
https://github.com/ellelstone/elles_icc_profiles/blob/master/profiles/Rec70...


It is the only one I've found that appears to have the correct linear "knee" in the near black area. It seems many other profiles, including those that Adobe distributes, are using an incorrect gamma curve.



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