[argyllcms] New user questions on display calibration

  • From: "Eric Fishwick, CLSA" <eric.fishwick@xxxxxxxx>
  • To: <argyllcms@xxxxxxxxxxxxx>
  • Date: Tue, 18 Aug 2009 09:19:55 +0800

I've been investigating argyllCMS for use to calibrate my screen and
printer. I have an i1Pro (with the most basic GM software). I use
Lightroom 2. 

I have been referencing the on line Argyll documentation and Marcel
Patek's guide here: http://www.marcelpatek.com/argyll.html
<http://www.marcelpatek.com/argyll.html>  but my knowlege of the
mechanics of colour calibration is basic, despite google. 

I have calibrated my monitor using dispcal. My understanding is that
this involves 

(1) Setting the RGB gains and biases in the monitor (if possible) to
achieve as close to 6500k (or whatever) at 100% white. I actually didn't
do this as I have an LCD panel so I left it at its native white point to
maximise dynamic range. So all I really did therefore was adjust
backlight brightness to get 100% white to a sensible level.

(2) Running the calibration routine to set grey scale to the desired
gamma (2.2 for me) and correct grey scale tracking so that all shades of
neutral grey have the same colour temp (as 100% white)

(3) Loading the created .cal file into the video card's LUT. 

I then generated an icc profile using targen, dispread and colprof. 

May I ask some questions so that I'm clear what I've done in this

-         Is my understanding of what dispcal does correct, if so how
does the icc profile add to this 

-         I used the -as switch (mainly because www.
<http://www.marcelpatek.com> marcelpatek.com gave it as example) to
generate a "shaper+matrix" profile. How does this differ from any other

-         The Argyll docs imply that the .cal file (from the
calibration) is embedded in the .icm file and is redundant, am I reading
this correctly?

-         For non-colour matched apps and the desktop am I right in
thinking that only the calibration part applies ie I now have gamma and
grey scale tracking correct but other colours might be off...

-         And that for icc aware apps all colours should be corrected
for the inaccuracies of the display (but corrected to what reference - I
shoot raw?) 

-         Is Lightroom 2 such an icc aware application (I assume yes but
can't find this anywhere in the LR help files).

One last question when I get around to profiling the printer. 

Colprof has an option to include a source icc, it has 2 switches and the
help states:

 -s src.icc <file:///F:/Argyll_V1.0.4/doc/colprof.html#s#s>    Apply
gamut mapping to perceptual B2A table for given source
 -S src.icc <file:///F:/Argyll_V1.0.4/doc/colprof.html#S#S>    Apply
gamut mapping to perceptual and saturation B2A table

Trouble is, I haven't a clue what this means. Which if any is
appropriate? Or is this irrelevant and I should just calibrate the
printer without a source icc profile. The printer is a Canon i9950
inkjet, my understanding is that its gamut is greater than the screens. 

My purpose in this is to have what I see on screen in Lightroom (hich
doesn;t soft proof) as close to what I get printed as possible. 

Thanks in advance for all your help.



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