[argyllcms] Re: Need help figuring out just why my profile isn't working
- From: Leonard Evens <len@xxxxxxxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sun, 14 Dec 2008 16:12:53 -0600
On Sun, 2008-12-14 at 21:14 +0000, Alastair M. Robinson wrote:
> Hi :)
>
> Leonard Evens wrote:
>
> > There is no question that the calibration information is being
> > loaded. It is what the applications are doing with the profile that
> > seems to be questionable.
>
> Or what the profile itself is describing. A monitor profile is only
> valid for the calibration state for which it was produced - and from
> what you said about the image on screen looking like it's been
> overcorrected, I suspect your profile has been built to describe the
> monitor in an uncalibrated state.
>
> The Calibration step is, in fact, optional - it's perfectly possible to
> build a profile to describe the monitor in any state of calibration -
> though the results are generally better after calibration.
>
> To try and pin this down a little further, can you try the following:
> Display a greyscale image of some kind ramp in an un-colour-managed
> application, then do this:
> dispwin -c
> (resets the LUTs with a linear ramp)
> Do you see a colour cast to the ramp? Give your eyes a few moments to
> adapt before deciding!
>
> Then:
> dispwin -L
> (Loads your profile, assuming you've installed it with dispwin -I at
> some point.)
>
> Do you see a change in the display?
> Do you now see a different colour-cast in the greyscale,
Yes.
> or is it now
It is closer to correct.
> correct?
>
> If you see no change, can you try this:
> dispwin /path/to/file.cal
> (Load the LUTs using the .cal file created by dispcal.)
There is no discernible change between
dispwin -l
and
dispwin xxxx.cal
where xxxx.cal is the calibration file with which the profile was
created.
In this case I used the targen, dispread, colprof sequence to produce
the profile, and I definitely used the -k option.
Perhaps I should remark that I am now up to W in my lettering having
started on this occasion with D. Last year I got to C and stopped
there with what seemed an acceptable calibration/profile at the time. So
there has been no want of trying.)
>
> If the effect of this is any different from dispwin -L then your profile
> doesn't correctly contain the LUT data - the most likely cause of this
> being the omission of the -k parameter when creating it.
>
> Another thing to try:
> dispwin -L
> (to set the X monitor profile atom)
> xgamma -gamma 1.0
> (to load the LUTs with a linear ramp - could also use dispwin -c for this)
> Now display a greyscale ramp in a Colour-managed application. Do you
> still see a colour cast?
It is actually worse that way.
>
> Hope this is some help,
>
> All the best,
> --
> Alastair M. Robinson
Well, these were interesting things to try. I am beginning to fear that
my problem will only be resolved after I completely understand in the
goriest detail exactly what all these programs are doing and how they
relate to what I see.
I also wonder if somehow the problem is me. When I had cataracts,
everything had a slight yellow cast, but my cataracts were removed in
2001. Also, I remember when I did color printing in my darkroom, 25
years ago, I had great difficulty getting rid of color casts in gray
scales, despite using an expensive color analyzers. I seemed to be
specially sensitive to very small color shifts, as small a .025 in color
filter units (if I remember the scale correctly).
It could also have something to do with ambient light.
--
Leonard Evens <len@xxxxxxxxxxxxxxxxxxxxx>
Mathematics Department, Northwestern University
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