Re: FWA / OBA compensation, user expectations
Re: FWA / OBA compensation, user expectations
- Subject: Re: FWA / OBA compensation, user expectations
- From: Jan-Peter Homann <email@hidden>
- Date: Mon, 18 Apr 2011 17:45:05 +0200
Hello Tom and all,
Your statements are correct. If we have very controlled environments in
a closed usergroup, with e.g. all users are using viewing booth from the
same vendor, we can calculate and exchange ICC profiles and setups of
process control, which are tailor made for this closed usergroup.
But if we are looking to the standardized print production (which is my
personal focus), we have to deal with viewing booths from different
vendors and standard D50 characterization data provided from FOGRA and
IDEAlliance.
Even if the standardized print production is not perfect today
(especially in dealing with FWA / OBA), I see e.g. well working
production workflows for coated papers with moderate FWA / OBA content.
Proof to Print match is fine even if the proof is made on media with no
/ very low FWA / OBA and also Softproof to Print match is fine is
current avaliable characterization-data and standard ICC-profiles.
Problematic is currently especially the workflows for e.g. uncoated
papers with very high amount of FWA / OBA.
My main intention is to improve workflows in the area of the
standardized print production according ISO 12647, if we have found a
solution for this area, we can look forward to use cases with closed
user groups, which are going beyond such workflows.
Best regards
Jan-Peter
PS: Argyll also provides a tool "spe2cie" wich applies the ArgyllCMS
method of FWA / OBA compensation during the step of converting spectral
data to L*a*b
Am 18.04.11 17:17, schrieb Thomas Lianza:
Hi Peter,
The problem is "what are we trying to communicate"? If we assume that
we want to communicate the appearance of a color under a hypothetical
light source such as D50, we run the risk of communicating the wrong
data because there is no such thing as physical D50 source. Reading
Graeme's excellent paper, points to a problem we have always had in the
whole workflow: We assume D50 and view under a rather deficient
simulation of D50. We can compensate heuristically based upon some
targeted variables, but there is still the potential to make some rather
large errors in a real life.
In the case of the OBA issue, the question is: Do we bother with the
booth or do we correct for it? If we share the same viewing illuminant
and media on both producer and consumer side, the issue is basically
eliminated as long as we reproduce the color numerically in the proof.
If the illuminant and media are different (Design->Production), there
will to be some issues.
Now with respect to ICC workflows Graeme wrote the following:
"In practice it is possible to compensate for the color shift that
results in viewing the media under non-D50 illumination or using a non
1931_2 observer, or allowing for FWA effects without severe
incompatibility because all rendering intents except absolute rendering
normalize to the media color, rendering the media white as white, even
though the absolute values are not measured using a D50 illuminant."
This is quite correct, but one would assume that absolute intent is what
is required proofing. The key is to understand the booth illuminant and
it's uv content. Not a trivial issue.
Regards,
Tom
-----Original Message-----
From: colorsync-users-bounces+tlianza=email@hidden
[mailto:colorsync-users-bounces+tlianza=email@hidden] On
Behalf Of Jan-Peter Homann
Sent: Monday, April 18, 2011 10:22 AM
To: colorsync-users
Subject: Fwd: Re: FWA / OBA compensation, user expectations
Hello Tom and all:
Most tools I have seen, are using the terms FWA / OBA compensation or
-correction in a workflow, where (mostly M0) spectral data is converted
to D50 L*a*b* values with an internal applied fomula for compensation or
correction of FWA / OBA
The results could e.g. be, that the spectral data of the paperwhite is
normaly converted to e.g. L* 95 a*1 b*-8. The conversion with
compensation will lead e.g. to L* 95 a*0 b*-3
So far a s I know, there are no ISO or CIE recommendations for a formula
to calculate OBA/FWA compensation -correction form (M0) spectral data.
So every vendor uses his own model / formula.
The open source tool ArgyllCMS uses a model / formula which has been
published as white paper . The ArgyllCMS documentation has a special
chapter about FWA / OBA compensation / -correction:
http://www.argyllcms.com/doc/FWA.html
Best regards
Jan-Peter
Am 18.04.11 13:26, schrieb Tom Lianza:
I am a little confused by your use of the word "compensation" in
point 3.
What does this mean?
On 4/18/11 7:09 AM, "Jan-Peter Homann"<email@hidden>
wrote:
3) OBA / FWA compensation independent from profile generation
***************************************************************
I think, it makes a lot of sense, when the FWA / OBA compensation
can be
applied to the measurement-data, before the ICC-profile is
calculated.
This allows e.g. to extract target values for process control in
hardcopy-proofing and softproofing from the compensated
measurement-data.
4) Avialable tools for FWA / OBA compensation
***********************************************
Following tools are e.g. avaliable for FWA / OBA compensation from
spectral measurement-data:
- Heidelberg Color Tool (commercial)
- Argyll CMS (open source)
- XRite i1 isis with OBC (commercial)
(If other tools are avaliable, please feel free to notice us, in
this
e-mail)
--
---------- Please note the new adress --------------
homann colormanagement --------- fon +49 30 611 075 18
Jan-Peter Homann ------------ mobile +49 171 54 70 358
Cotheniusstr. 3 -------- http://www.colormanagement.de
10407 Berlin -------- mailto:email@hidden
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden