RE: Re: FWA / OBA compensation, user expectations
RE: Re: FWA / OBA compensation, user expectations
- Subject: RE: Re: FWA / OBA compensation, user expectations
- From: Thomas Lianza <email@hidden>
- Date: Mon, 18 Apr 2011 11:17:11 -0400
- Thread-topic: Re: FWA / OBA compensation, user expectations
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)
>>
>>
--
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