[argyllcms] Re: Capture One Profiles

  • From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sat, 6 Jul 2013 11:55:28 -0700

On Jul 6, 2013, at 11:24 AM, Maciej Bryński <maciek@xxxxxxxxxx> wrote:

> I can manually approximate correct WB. But is there a method to count
> it exactly ?

Yes and no.

You can precisely normalize white balance and exposure both by building a 
profile of a UNIWB gamma 1.0 development of the file; looking up D50 white in 
said profile; and doing a bit of math on the resulting RGB values.

The catch is twofold.

First, I have no clue what sorts of math would be necessary to translate into 
some white balance / tint slider positions; second is that I don't even know if 
C1 offers the ability to do the kind of minimalist processing you need. 
(Basically, you're looking for a file that's undergone demosaicing and nothing 
else.)

If you can't do it right, you can at least get pretty close by cranking the 
saturation, fiddling with the sliders until it looks as least awful as you can 
get, and returning the saturation back to normal. It helps to have a 
synthetically-generated reference image on the same screen to compare with. 
You'll also want to adjust the exposure slider so that the luminance of neutral 
patches are as close a fit as possible, and you'll likely want to bounce back 
and forth between adjusting white balance and luminance until you reach a point 
of diminishing returns.

Boosting saturation visually exaggerates color differences, especially of those 
close to the neutral axis. An image whose white balance is even slightly off 
will look really bad when you crank the saturation. If the white balance is 
perfect, it'll just look very saturated.

More details -- too many more details -- here:

http://trumpetpower.com/photos/Exposure

Cheers,

b&

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