[argyllcms] Re: Scaled Rec709 TRC question

  • From: János, Tóth F. <janos666@xxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 14 Feb 2011 15:13:22 +0100

Yes, Alexander.

I already wrote a Little CMS plugin which extends the supported curve types
with the mathematical function of the Rec709 curve (and it's inverse

I set up the original Rec709 Curve parameters.

(By the way, I tried to use it --- the exact inverse encode --- in bright
room but it looked bad anyway. But never mind, may be it's just me and may
be only because I used the pure-power curve for so long...)

May be I should try to use CIECAM02 then.

But it sounds much easier to set up those three ambient view condition
presets with fixed curve parameters.

Otherwise, I can't really believe in CIECAM02 here because it's much younger
than Rec709. (There is no way that Rec709 has anything to do with CIECAM02.
At least officially...)

So, I think: If the "scaled inverse encode curve" is really meant to be used
on the end-user side, then there should be a commonly accepted/suggested way
for this scaling method. (Which had to be exist long before CIECAM02...)

And another concern of mine that this curve is well defined but otherwise
"hard to scale". It wouldn't make me think that I should use it in a scaled
form. (Or where are the scaling formulas and/or the suggested curve
parameters then...?")

Another idea is to plot the curves and play with the parameters until it
looks like this:
(Unfortunately his link is dead now. But I can do the same thing with
mathcad or excel. I just don't like to do these kind of things myself. -> I
am a very bad faker so I am always aware of the fact when I am faking
something. And I want it to be done "properly". :D)

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