[Lcms-user] Re: scanner calibration and "possible inconsistency"

[<ma...@li...>]

Hi,

I'm also forwarding this to mailing list.

> I have had the opportunity to calibrate a scanner using two different
> ransparency targets, one profesional, one from Wolf Faust. I'm not
> saying that the latter is not professional, but anyway:
>
> My calibration profile produced with professional software and the
> first target seemed OK, but using the latter target (E0105111 I think)
> produced a questionable result regarding the Red Colorant rXYZ.
>
> First I thought it's a bug in the software, but yesterday I used the
> free tools to produce a measurement sheet, and then a profile. During
> that process I got a warning about a "possible inconsitency", so I
> wonder if the target or the target description data has a problem.

Doublecheck if you are mismatching target sheets. I have done several
testing with Wolf's targets and they are clear winner on accurancy and
big gamut. This warning is issued when regression is not convergent,
that could be a clue of wrong target sheet selected.
Also note that reflective and film are completly different. If you are using
reflective sheet and a film target, you will find this kind of problems.


> Unfortunately the free software does not allow to save the output of

For saving output of progress, right click over text, click on "Select All",
right click again, click on "Copy" and then paste text on your favourite
text editor.

> "Progress". Also I could not use the 16bit per RGB TIFF, but had to
> convert it to 8bit/channel PNG.
>

Yes... measurement tool is very limited. This is in part due I'm using Qt
for portability. Unfortunately, Qt support on imaging is minimal.
No TIFF, no 16 bps in any way and a few supported formats. Otherwise
measurement tool functionality is quite simple: It only reads pixels and
creates a IT8 sheet containing RGB values per patch.

I did separate programs in order to better the profile generation, leaving
the RGB collection in a second plane. This has been my fault, since for
now seems evident a carefull RGB picking plays a vital role. 16 bps
would be a big improvement, specially on dark zones. Also some
processing instead simple mean value seems more adequate.

But as said these are measurement tool limitations. The scanner & monitor
profiles does not have such limitations since they read IT8 files and does
write profiles. Probably measurement tool should be almost fully rewritten
for next revision.

Any thoughts?

Regards,
Marti Maria


----- Original Message -----
From: "Ulrich Windl" <Ulr...@rz...>
To: <kw...@co...>
Cc: "Martí Maria" <ma...@li...>; <wf...@co...>
Sent: Tuesday, February 12, 2002 4:05 AM
Subject: scanner calibration and "possible inconsistency"


> Hello,
>
> I have had the opportunity to calibrate a scanner using two different
> ransparency targets, one profesional, one from Wolf Faust. I'm not
> saying that the latter is not professional, but anyway:
>
> My calibration profile produced with professional software and the
> first target seemed OK, but using the latter target (E0105111 I think)
> produced a questionable result regarding the Red Colorant rXYZ.
>
> First I thought it's a bug in the software, but yesterday I used the
> free tools to produce a measurement sheet, and then a profile. During
> that process I got a warning about a "possible inconsitency", so I
> wonder if the target or the target description data has a problem.
>
> Unfortunately the free software does not allow to save the output of
> "Progress". Also I could not use the 16bit per RGB TIFF, but had to
> convert it to 8bit/channel PNG.
>
> I'm quite new to all those topics, so giving me some useful advice
> would be great. I could also provide more data if you should need such.
>
> Regards,
> Ulrich
>
>
>