[argyllcms] Re: fwa compensation unexpected results
- From: "Gerhard Fuernkranz" <nospam456@xxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 5 May 2006 18:15:59 +0200 (MEST)
> --- Ursprüngliche Nachricht ---
> Von: Graeme Gill <graeme@xxxxxxxxxxxxx>
>
> [...]
> If you were intending to view the prints under standard tungsten
> lighting, then 'A' would be appropriate. I think quartz halogen is
> a little hotter though.
Graeme,
I think you've mistakenly mixed up "-i" and "-I". In the spec2cie utility I
had contributed, the capital "I" option permits overriding the instrument's
light source spectrum, i.e. the light source used by the instrument when it
takes the measurements. The default (if -I... is not specified on the
command line) is the light source assoiciated with the instrument type given
in the input .ti3 file. I had added this option 1. for experimental
purposes, and 2. because it looks like some instruments can use not only a
single, but different, selectable light sources (e.g. with or w/o UV filter
in the illumination path, or e.g. Spectrolino with D65 filter).
So if "-I" is specified, then it should refer to the actual light source
spectrum used by the instrument when it takes the measurements. For many
instruments with a tungsten lamp, I guess ill.A may be a good approximation,
but if an UV filter is in the play, then specifying an UV filtered ill.A
spectrum instead would IMO be more appropriate.
(I have some doubts though, whether the FWA compensation will still work as
well for measuments that have been taken with an UV filterered instrument,
even if the actual (filtered) instrument light source spectrum is used for
computing the FWA compensation. I'm afraid that the prediction accuracy of
the FWA compensation will rather suffer in this case. What do you think?)
Regards,
Gerhard
--
Gerhard Fuernkranz
nospam456@xxxxxx
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