Re: Profile verification in PatchTool
Re: Profile verification in PatchTool
- Subject: Re: Profile verification in PatchTool
- From: "dpascale" <email@hidden>
- Date: Sun, 4 May 2008 16:57:43 -0400
Hello Marco,
When the RGB data are opened in PatchTool, the user is asked to assign one
of 5 possible working spaces. The choice is limited to AdobeRGB, Apple
RGB, Generic RGB, ProPhoto RGB, and sRGB, and does *not* include the
monitor profile or any of the other RGB profiles in the user's ColorSync
profile folder.
At any rate, choosing the monitor profile as source for the opened RGB
data in Display Check is the same as assigning it, say, in Photoshop,
>correct?
When you open a list which has only RGB data, you are asked, as you mention,
to select among five standard RGB files to convert the RGB data into XYZ
(because there is no profile attached to a color list). And yes, assigning
one of the standard spaces is exactly the same as assigning the profile in
Photoshop (these are exactly the same as the matrix based profiles for these
spaces, but generated by PatchTool internally); the difference with
Photoshop is that you cannot assign any external ICC profile to the input
file.
"To check for your profile accuracy, select your display profile as both
the source and destination. In theory, the difference between the
references >and the measured data should be zero for a perfect profile and
if nothing has changed since calibration."
The only RGB data which you can send with no color management, with the same
source and destination profiles, are the preset RGB lists in "QuickTest".
The reference you give from page 49, reproduced above, is in a section about
QuickTest.
By the way, while I'm very clear on the the reason for selecting a source
profile, why are we required to choose a *destination* profile in
>DisplayCheck, given that the measured data are already device-independent
and ready to be used as is without further conversions?
Source profile is only required for QuickTests, which are based on
internally generated RGB values not assigned to any space. A source profile
is then required in order to obtain device independent values from it (i.e.
XYZ / L*a*b* D50). The difference between Quicktest RGB files and RGB files
that are opened with PatchTool, is that the assigned profile can be either
built-in or user-selectable. This device independant data obtained with the
Source profile is then processed by the output profile to get the display
RGB that is sent to the monitor (XYZ-D50 ---> DESTprofile ---> RGBdisplay).
.
For ALL opened files, once opened, the file data is based on XYZ. For
display and measurement purposes, it needs to be converted to
color-corrected RGB values, using the destination profile (XYZfile --->
XYZ-D50 ---> DESTprofile ---> RGBdisplay). I do not see how you cannot use a
destination profile This is a separate issue than how the measured data is
processed.
Danny
email@hidden
www.babelcolor.com
----- Original Message -----
From: "Marco Ugolini" <email@hidden>
To: "dpascale" <email@hidden>
Cc: "ColorSync Users Mailing List" <email@hidden>
Sent: Sunday, May 04, 2008 3:07 PM
Subject: Profile verification in PatchTool
Danny Pascale wrote:
Marco,
When making a check from an opened file, the reference data is always XYZ
(or L*a*b*) based, and the source profile is thus L*a*b*/PCS.
A source profile needs/can only to be assigned for the "Quick" test, which
use RGB in the source profile as reference.
Hi Danny.
This is what I find on page 49 of the PatchTool manual (in PDF format):
"To check for your profile accuracy, select your display profile as both
the source and destination. In theory, the difference between the
references and the measured data should be zero for a perfect profile and
if nothing has changed since calibration."
When the RGB data are opened in PatchTool, the user is asked to assign one
of 5 possible working spaces. The choice is limited to AdobeRGB, Apple
RGB, Generic RGB, ProPhoto RGB, and sRGB, and does *not* include the
monitor profile or any of the other RGB profiles in the user's ColorSync
profile folder.
At any rate, choosing the monitor profile as source for the opened RGB
data in Display Check is the same as assigning it, say, in Photoshop,
correct?
By the way, while I'm very clear on the the reason for selecting a source
profile, why are we required to choose a *destination* profile in
DisplayCheck, given that the measured data are already device-independent
and ready to be used as is without further conversions?
Thank you, and all the best.
Marco
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