Re: Profile verification in PatchTool
Re: Profile verification in PatchTool
- Subject: Re: Profile verification in PatchTool
- From: Marco Ugolini <email@hidden>
- Date: Mon, 05 May 2008 00:09:57 -0700
- Thread-topic: Profile verification in PatchTool
In a message dated 5/4/08 1:57 PM, dpascale wrote:
> 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.
Hi Danny.
I'm still unclear on the procedures used by PatchTool. Let me explain why.
Monitor profile validation procedures that use RGB lists send the RGB
numbers to the display directly, *as is*, without conversion and without
assigning any profile to them.
In this scenario, assigning the monitor profile to the RGB reference data is
only required in order to produce a list of *reference Lab data* (the Lab
values that the profile expects from those RGB numbers) -- which are later
compared to a list of Lab values measured off the monitor with the
colorimeter. The difference between reference (expected) values and measured
(actual) values provides the final DeltaE values.
Simply stated, the purpose is to check how close the results of the monitor
profile's A2B tables are to the actual measured values (if the monitor
profile is LUT-based).
In this procedure there is no conversion of the RGB reference data to the
monitor profile. The active monitor profile is automatically "assigned", in
a manner of speaking, to the RGB numbers at the OS level, but the RGB data
are *not* converted to the active monitor profile from another profile (say,
sRGB).
For these reasons, I fail to understand the purpose of *converting* the RGB
reference data from an assigned working space (like sRGB, for example) to
the monitor profile when performing a profile validation routine. In this
light, it seems redundant, an unnecessary extra step that is not taken by
RGB-list-based monitor profile validation routines.
All the best.
Marco Ugolini
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