[argyllcms] Re: Number of patches - well behaved printer?

  • From: Iliah Borg <ib@xxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 23 Feb 2011 20:09:14 -0500

Dear Rishi,

> But when you're building a profile from a Velvia IT8 target, say,
> you're really trying to measure the tone response curve of your
> scanner, not of the film, right?

To build tone reproduction curve it is better to use something like Kodak #2 
grey step wedge (tone is b/w reproduction)

Profiles are addressing scanner+film+target development, one can't really 
separate one from the other at this stage and using ICC. It is important to 
realize that Wolf's development and your development are different; and 
different enough. Creating the profile for a scanner we actually only try to 
map the colour gamut of the film. Tone curve is an artistic decision as Graeme 
rightfully pointed out; and more than colour. Image lives or brakes on 
contrast. We have a b/w film which is something we can use - but try using ab 
channels without L ;)

> I thought that after recording the
> IT8 chart on the film, Wolf Faust measures the spectral data of the
> patches on the film using a standard illuminant, then stores these XYZ
> values in a measurement file that the profiling software then uses to
> map the scanned values to the spectral values.


> This means that the
> scanner is trying to recreate the colors on the film, not the colors
> of the original chart

Profile is between measured values and scanned values, mapping scanned values 
to measured values. So it reproduces the chart. If the chart accurately covers 
the media gamut like Don's charts do - you are very likely to get a profile 
that allows to render the abilities of the film pretty accurately.

Iliah Borg

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