RE: Why 2 degree observer measurements for ICC profiles?
RE: Why 2 degree observer measurements for ICC profiles?
- Subject: RE: Why 2 degree observer measurements for ICC profiles?
- From: "Wayne E. Bretl via colorsync-users" <email@hidden>
- Date: Mon, 22 Jul 2024 17:41:36 -0700
The difference between a natural lens, a replacement lens with UV
absorption, and a clear replacement can be very large in daylight vs. other
sources. I got UV absorbing lenses in both eyes, and during the time I had
only one replacement, the difference was quite noticeable. A colleague who
had one UV absorbing and one clear reported some extreme differences. I had
a khaki colored parka that was mainly cotton, but synthetic knit for the
collar. In daylight, I saw a slight mismatch, but he saw a strong purple
cast to the collar.
I wear photo gray glasses, and I can see an amber tint under artificial
light and a much stronger amber tint under daylight. My natural lenses had
browned to the point that I could not see the tint.
-----Original Message-----
From: Graeme Gill via colorsync-users <email@hidden>
Sent: Monday, July 22, 2024 5:29 PM
To: ColorSync <email@hidden>
Cc: Graeme Gill <email@hidden>
Subject: Re: Why 2 degree observer measurements for ICC profiles?
Peter Miles via colorsync-users wrote:
> Is there a way of qualifying what sort of size colour differences
> these observer variations are causing in the normally sighted
> population? If they were all looking at the same objects in a viewing
booth, what sort of magnitude of potential colour differences would they be
seeing?
In some numerical simulations I've done, this depends heavily on how narrow
band the colors are. Make them very narrow (such as lasers) and you can
expect extreme differences in perceived color (I saw of the order of 30 dE
for some observer pairs).
Of course a print evaluation is the least provocative situation since
typical colorants used on paper have relatively mild transitions vs.
wavelength. This is why reflective and transmissive media that uses typical
pigments or dyes has smaller gamuts than emissive displays or interference
effects filters.
> FYI: A few years ago I had a lens replaced in one of my eyes and so I
> now have two quite different 'observers' when it comes to assessing
colour.
How different this will be in practice depends on how "bumpy" the difference
in the transmission spectra of your two lenses are. A smooth difference will
amount to a change in white point, but is less likely to change what you
regard as a colorimetric match. More rapidly changing differences could have
some effect, depending on the coincidence between those differences and the
transition bands of the color stimulus.
Cheers,
Graeme Gill.
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