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: Refik Telhan via colorsync-users <email@hidden>
- Date: Fri, 02 Aug 2024 15:46:47 +0300
- Thread-topic: Why 2 degree observer measurements for ICC profiles?
Hi Peter,
There have been several attempts made by the scientific community to quantify
observer metameric mismatch during the past couple of decades.
Finally IEC (International Electrotechnical Commission) has published the
technical specification on 2023-11-01 as “IEC TS 61966-13:2023”.
(https://webstore.iec.ch/en/publication/67769)
--------------------------
IEC Technical Specification 61966-13
IEC TS 61966-13:2023
Multimedia systems and equipment - Colour measurement and management - Part 13:
Measurement method of display colour properties depending on observers
IEC TS 61966-13:2023 defines an objective colour difference metric and a
measurement method for observer metamerism caused by displays with different
spectral power distributions. This document also specifies the measuring
equipment, conditions and methods that are necessary to obtain the metric. This
document applies to light-emitting or backlit transmitting colour displays
measured under dark-room conditions.
--------------------------
You can read more on the topic in a recent issue of the ID magazine published
by The Society for Information Display (Volume 40, Issue 1,
https://sid.onlinelibrary.wiley.com/toc/2637496x/2024/40/1)
The above technical specification is mentioned in the article “Measuring
Subjective Differences Objectively” by Johan Bergquist in the same issue.
https://sid.onlinelibrary.wiley.com/doi/10.1002/msid.1453
Johan Bergquist happens to be one of the members of the technical committee
that developed the specification.
https://www.iec.ch/dyn/www/f?p=103:14:510370051608773::::FSP_ORG_ID,FSP_LANG_ID:28215,25
The January/February 2024 issue of the ID Magazine is dedicated to
“Understanding Wide Color Gamut Displays”.
At this point in time, I am not aware of the presence of any measurement device
that is capable of measuring/reporting the OMMI (Observer Metameric Mismatch
Index) out of the box.
“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?”
Viewing real product samples, inkjet contract proofs or real prints in a
viewing booth is somewhat a different ball game. Observer metameric mismatch is
related with the interaction of the individual CMFs of the observers and the
spiky nature of the SPDs of the pigments in the product/inkjet inks and
printing inks. We just have to assume that the viewing booth has a full
spectrum very high CRI light. Hence the visual mismatch between what the
observers is seeing will be related to the spectral structures of the pigments.
Visual mismatch takes place when the narrow band peaks of the incoming light
hits the CMFs of different individual observers at different points.
Best regards,
- Refik
PS. I have sent this message originally on 28 July 2024. However, the iCloud
mailing system only sent the notification today that message has not been
delivered. Hope it will reach its destination this time.
-----Original Message-----
From: Peter Miles via colorsync-users <email@hidden
<mailto:email@hidden>>
Reply-To: Peter Miles <email@hidden <mailto:email@hidden>>
Date: 22 July 2024 Monday 09:07
To: ColorSync <email@hidden
<mailto:email@hidden>>
Subject: Re: Why 2 degree observer measurements for ICC profiles?
Thanks Graeme, and everyone for your responses. A lot of food for thought.
Refik
I had a looked at the “Individual Colorimetric Observer Model” paper, however I
don’t have a training in color science to fully grasp the significance of what
I am reading.
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?
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.
Thanks
Peter Miles
From: Graeme Gill via colorsync-users <email@hidden
<mailto:email@hidden>>
Date: Friday, 19 July 2024 at 8:49 PM
To: ColorSync <email@hidden
<mailto:email@hidden>>
Subject: Re: Why 2 degree observer measurements for ICC profiles?
Peter Miles via colorsync-users wrote:
> So why do ICC profiles, for print production, still use 2degree observer
> measurements instead of 10 degree observer measurements?
A standard often has a momentum of its own. But in the case of color in media
that is looked at in detail (such as images), 2 degree is appropriate.
AFAIK, one of the reasons that the 10 degree observer is often recommended is
that it was created with more observers and in a more refined way, and is
technically
a bit more accurate. In subsequent experience it has often turned out that the
10 degree standard matches people more accurately than the earlier 2 degree
observer, even though it is not the appropriate viewing angle.
Note that there are many subsequent more refined standards or proposed standards
such as the 2012 2 and 10 degree observers. These are not in widespread use
though,
whereas every graphic arts instrument will return 1931 2 degree values.
And of course there is nothing to stop you making ICC profiles using any
observer you like :-) They may not be technically interchangeable with
profiles using the 1931 2 degree observer, but that matters less in practice,
and not at all if all the profiles you use the same observer.
Cheers,
Graeme Gill.
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