[argyllcms] Re: help with camera profile

  • From: Alberto Ferrante <alberto.ferrante@xxxxxxxxxx>
  • To: "argyllcms@xxxxxxxxxxxxx" <argyllcms@xxxxxxxxxxxxx>
  • Date: Fri, 03 Aug 2012 10:38:36 +0200

Dear Stephen and Iliah,

>> "Cannot the problems with shadows/highlights be related with the dynamic 
>> range of the camera?"
>> No single exposure of a test chart can fully exercise the dynamic range
> But 2 exposures separated by 4 or 5 EV (depending on the camera) wiil.

That was exactly what I was thinking about, Iliah... But how can
multiple exposures be merged effectively to generate a camera profile?

> I have not yet experienced shadow problems with matrix profiles. My profiles 
> render shadows too light and I simply apply an RGB tone curve (in the RGB 
> working space) to darken the shadows, increase contrast in the mid-tones, 
> smoothly roll-off the highlights and even adjust exposure.

I have pretty much the same settings as you at the moment, but I also
need quite some saturation to have acceptable visual results. I smooth
highlights by using the "film" clipping of ufraw, that is the only
method that seems to work well. A the moment, after a number of tests, I
decided to use single shaper profiles. Matrix only profile were giving
strange results expecially on highlight zones (blue cast). I also tried
a LUT profile (-al) that seemed very good, but I soon discovered that
all highlights assumed a fluorescent green tint, that is not exactly

I am now waiting for the colorchecker passport to arrive.

Best regards,

Home page: http://www.alari.ch/people/alberto
Photo galleries : http://albertoferrante.name
Public key: http://www.alari.ch/people/alberto/keys/yahoo.asc

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