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Re: Color space problems again

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Andrew Somers
Re: Color space problems again
on Sep 6, 2018 at 11:00:38 am

JERRY SAID: My understanding is they just use a generic sRGB profile to display the mp4


They don't use any profile AT ALL.

A "profile" implies color management, and video is normally NOT color managed. Video is normally "rendered with a specific display target".

What is color management: Color management is a process where ICC color profiles are used to convert image date from one color space to another color space, using either a "connection color space" or a "device link".


What is rendering for a specific target: This means the image data is rendered in such a way that when played back through a specific target device without further manipulation, it looks as intended. A "specific target device" means an sRGB monitor, or a Rec886 monitor, etc.


When you work with color management turned off, then you are de-facto working to render to a specific target — this means that your display monitor must be of the same target that is your render intent. You chose an sRGB monitor, so that *particular* sRGB monitor becomes your render target. Ideally you have used a hardware profiling device to create a system profile specific for that monitor so that it is as close to the baseline sRGB target as possible.

After Effects default for import of non-tagged images is sRGB. This can be changed in the "interpretations rules.txt" file.

Some other things I want to clear up: Just because your animation movs are untagged does NOT mean they have no color space — they certainly do!! They have a gamma curve and look the way they do based on the color primaries of your target.

Also: sRGB and Rec709 have identical whitepoint and color primaries. The ONLY difference is the transfer curve (aka gamma). Rec601 and Rec709 have identical transfer curves and whitepoint, but they have very slightly different color primaries (slight enough that it is common for Rec601 to simply be interpreted as Rec709).


As for your streaming encoder assuming any particular profile: is it CHANGING the look on output? What encoder are you using?

Andrew Somers
VFX & Title Supervisor
http://www.GeneralTitles.com


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