How feasible is this procedure?

Hi,

>  Basically, it assumes that one can generate an
accurate color profile for 
> a digital camera, and then turn around and use it as a
colorimeter to 
> profile your monitor.

I tried something similar long time ago, but didn't work at
all.
The reasons were several, but mostly the error you get by
using
a camera is too big to get suitable profiles.

My work was largely based on CRT, and may not be valid for
TFT
since thet are basically differnt beasts, but here are some
ideas:

- An ICC profile for CRT monitor  can be built using just
  matrix-shaper.
- Average error of matrix-shaper can be really low,
sometimes
 under < 1dE. Again, that's for CRT only
- Gamma-gain-offset model works great if you can add an
offset to
 refresent black point.
- Primaries mismatch is not so important, what makes a
difference
(to the eye) is white point and transfer curves.

Putting all together, you can do a reasonable ICC profile
for a CRT
monitor by knowing white point, primary chromaticities and
transfer
curves. Primaries are on most CRT very close to Rec709
(sRGB)
so you have to know transfer function (aka gamma) and white
point.

The missing part is how to characterize white point and
transfer
curves without expensive hardware. I don't know either 
There has been some work on  that. See for example HP's
MIND
http://www.hpl.hp.com/techreports/1999/HPL-1999-158.pdf
But AFAIK there is still no clean solution.

Regards
Marti Maria
The littleCMS project
http://www.littlecms.com



----- Original Message ----- 
From: "Cory Papenfuss" <papenfussjuneau.me.vt.edu>
To: <lcms-userlists.sourceforge.net>
Sent: Saturday, March 04, 2006 3:48 PM
Subject: [Lcms-user] How feasible is this procedure?


> I got off on the monitor profiling tangent a bit this
morning, and as far 
> as I can tell, nobody gives a crap about linux-land
monitor colorimetry. 
> Argyll allegedly supports two devices, but they're
both old and expensive. 
> Ran across this idea:
>
> http://wiki.scribus.net/index.php/Proposal_for_M
onitor_Profiling
>
>  Basically, it assumes that one can generate an
accurate color profile for 
> a digital camera, and then turn around and use it as a
colorimeter to 
> profile your monitor.
>
>  Does this seem like a reasonable thing to do?  I'm
sure it's not as 
> accurate as a puck-like object stuck directly on the
screen, but with 
> minimal ambient light it may be reasonable.  The gamut
of DSLRs in 
> particular is comparable to CRT's, no?
>
>  Intriguing...
>
> -Cory
>
> -- 
>
>
************************************************************
*************
> * Cory Papenfuss                                       
                *
> * Electrical Engineering candidate Ph.D. graduate
student               *
> * Virginia Polytechnic Institute and State University  
                *
>
************************************************************
*************
>
>
>
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