[argyllcms] Measuring spectral transmission of lenses (and filters, too)

  • From: Iliah Borg <ib@xxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 25 May 2011 22:48:58 -0400

Dear Listmembers,

For raw conversion, I need to decide if I'm going to use lens / filters 
(polarizing filters are my primary concern) correction matrices over sensor 
"profiles" or not. To make up my mind I need to take measurements of spectral 
transmissions of different lenses and filters. Instrumentation I have is: i1Pro 
and Spectrolino/SpectroscanT. I'm not sure I can use the lamp in SpectroscanT 
(if you know it is possible please advise so), so I started with i1Pro.

From reading argyll/spotread documentation it seems that I can use emission 
mode, measuring separately the light source as a backlit and the light from the 
same source passing through the lens; than calculate the transmission dividing 
the pairs of numbers for each wavelength. As far as I understand no ambient 
light attachment is needed in this case.

Another option would be to use -t flag, however only DTP41T and SpectroScanT 
are listed for this flag (with the option to use Spectroscan with a separate 
backlit light). Does this mode works for i1Pro too? An attempt to run it with 
i1Pro caused no error messages, however the results are different from those 
obtained through spotread with -e flag (might be of course because in a quick 
experiment the lens was not placed to the same position).

Any comments and advice would be highly appreciated.

On a side note, running spotread from Argyll CMS 1.3.3 with -p flag /projector 
measurement mode/ (OS X 10.6.7) returned "unsupported for my i1Pro.

Iliah Borg

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