Re: New Optical Upgrade
Re: New Optical Upgrade
- Subject: Re: New Optical Upgrade
- From: "Bob Chase" <email@hidden>
- Date: Sun, 2 Mar 2003 20:37:57 -0500
The v3.7 update of Feb '03 currently on ColorVision's site is unrelated to
the recently discussed issues. However, ColorVision reports that, thanks to
discussions with Bruce Lindbloom, they are indeed working on fixing the
discrepancy with the D65 primaries tags - no date specified, but I would
imagine it will be available soon.
Additionally, I was provided an explanation for why the profiles produced
from the File menu are different in structure from the profiles produced
from the Calibration process (approx ~2000k versus Calibration-produced
profiles of ~500k.) In my opinion, the explanation was very good news, as
follows:
Per ColorVision: The profiles produced from the file menu are created with
256 point RGB Tone Response Curves built from measuring the corrected
display. The profiles from the Calibrate process instead use a 1-point
gamma that specifies the curve as a gamma value instead of individual
points. Some programs, at least in the past, did not like curve tags with
lists of points. Even programs that do handle the 256-point curve tags
usually just convert them into a gamma value for computation anyway.
I found this very interesting, and of course had to test for myself. What I
found was, in Photoshop v7, the profile with the 256 point curves provided a
little more separation in the dark shadows - which resulted in a distinct
visible separation from *each* level to the next - very, very nice! No
banding at all in my 256 level gradients!
In contrast, with the simple gamma curve profile (gamma 2.2 for me), there
were a number of shadow steps which were indistinguishable. So it's great
that OptiCAL provides users a choice.
Also, a monitor profile created by saving from the Photoshop Custom RGB
dialog is a simplified profile, using the 1-point gamma - so I can't update
the OptiCAL primaries in Photoshop without converting the profile to the
simplified version.
Therefore, I eagerly await the updated OptiCAL, so I can begin using the
File menu 256 point TRC profiles, at the very least in Photoshop.
---------------
Also, FYI:
ColorVision pointed out (thanks!) that there is finally an ICC profile
viewing utility available for Windows that is freely distributed, available
on the ICC website:
http://www.color.org/membersonly/profileinspector.html
Very useful! (double click the displayed tags to see their property
details...)
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