measured LAB Values compared to PS
measured LAB Values compared to PS
- Subject: measured LAB Values compared to PS
- From: David Remington <email@hidden>
- Date: Mon, 16 Feb 2009 10:44:35 -0500
How about measuring Lab values (Profile Maker measure tool) from
originals (artwork, manuscript material, vintage photographs, etc...)
and comparing to Lab values displayed in Photoshop? We use this
technique for a "second opinion" when matching digital captures to the
originals. We have the second set of values in the info pallet set to
Lab (working in RGB). Correcting to match the measured color looks
"right" (most of the time!). Originals are evaluated in GTI viewing
booths, and we use our own "best match to the booth" monitor settings
(5800-6000K/110-120/L*. Booths dimmed to about 50%. A couple sources
have confirmed that is technique should be valid, but in never hurts
to get the third, forth, or fifth opinion.
Thanks,
David
On Feb 13, 2009, at 3:04 PM, email@hidden
wrote:
------------------------------
Message: 5
Date: Thu, 12 Feb 2009 17:00:58 -0600
From: "Mike Stewart" <email@hidden>
Subject: LAB Values attained from Profiles
To: email@hidden
Message-ID:
<email@hidden>
Content-Type: text/plain; charset=ISO-8859-1
Can anyone tell me the proper way via Photoshop to read LAB values of
colour swatches usinf ICC profiles. Ex: If I wanted to know what the
LAB
values of a colour bar are supposed to be by using the US Sheetfed
Uncoated ICC Profile; what's the proper way in Photoshop to get the
actual
LAB values readings.
Thanks
Mike Stewart
------------------------------
Message: 6
Date: Thu, 12 Feb 2009 17:06:42 -0600
From: Matt Louis <email@hidden>
Subject: Re: LAB Values attained from Profiles
To: Mike Stewart <email@hidden>,
"email@hidden" <email@hidden>
Message-ID: <C5BA07A2.807F%email@hidden>
Content-Type: text/plain; charset="iso-8859-1"
In color settings (advanced mode) change the rendering intent to
absolute. Assign the US Sheetfed
Uncoated profile to the document you are reading from.
- Matt Louis
On 2/12/09 5:00 PM, "Mike Stewart" <email@hidden>
wrote:
Can anyone tell me the proper way via Photoshop to read LAB values of
colour swatches usinf ICC profiles. Ex: If I wanted to know what the
LAB
values of a colour bar are supposed to be by using the US Sheetfed
Uncoated ICC Profile; what's the proper way in Photoshop to get the
actual
LAB values readings.
Thanks
Mike Stewart
------------------------------
Message: 7
Date: Thu, 12 Feb 2009 23:22:12 -0800
From: Marco Ugolini <email@hidden>
Subject: Re: LAB Values attained from Profiles
To: Mike Stewart <email@hidden>
Cc: ColorSync Users Mailing List <email@hidden>
Message-ID: <C5BA5FA4.19ADC%email@hidden>
Content-Type: text/plain; charset="US-ASCII"
In a message dated 2/12/09 3:00 PM, Mike Stewart wrote:
Can anyone tell me the proper way via Photoshop to read LAB values of
colour swatches usinf ICC profiles. Ex: If I wanted to know what
the LAB
values of a colour bar are supposed to be by using the US Sheetfed
Uncoated ICC Profile; what's the proper way in Photoshop to get the
actual
LAB values readings.
There is no need to change Photoshop's color settings (which carries
the
risk that you may forget to change them back, and produce strange
results in
the rest of your work as a consequence).
Instead, leave your color settings alone. Just open the CMYK file
containing
the swatches for the solids, overprints and tints. Assign your chosen
profile -- US Web Coated (SWOP) v2, for example.
IMPORTANT: Do *not* convert! Just *assign*!
Then select Edit > Convert to Profile, choose "Lab Color" as your
destination profile, and select the Absolute Colorimetric rendering
intent
from the "Intent" pulldown menu. Click "OK".
The resulting values will account for the effects of the substrate
on the
colors, thanks to the use of the Absolute Colorimetric intent.
Marco Ugolini
------------------------------
David Remington
Manager, Digital Imaging and Photography Services
Digital Imaging and Photography Services
D-70 Widener Library
Cambridge, MA 02138
p 617-495-4701
f 617-495-0403
w http://imaging.harvard.edu
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