[argyllcms] Fwd: Question about M1 measurements

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 26 Aug 2014 16:19:49 +1000

Bill Birkett wrote:

> I'm wondering, what is your opinion of the M1 measurement standard. Does it 
> magically
> solve all OBA problems, as Idealliance seems to indicate, or is this just 
> another "FWA myth"?

        nothing can magically solve all OBA problems, short of using paper
that is free of FWA/OBE.

The bottom line is that paper that uses OBE/FWA has an appearance that
varies with the UV content of the illuminant it is viewed under. In color 
such media, it can therefore help if the the nature of the illuminant is known,
and the color measurement system is able to anticipate the appearance of
what is being measured under the actual viewing illuminant.

As I understand M0/M1/M2, it is an attempt to address the fact that
up till now, the impact of the UV content of the illuminant on
FWA/OBE has largely been ignored and uncontrolled in the graphic arts context.
Both "D50" viewing booths and "D50" instrument measurements
haven't actually taken any care of whether the "D50" matches
the D50 UV content. Introducing the M0/M1/M2 nomenclature
and standard at least makes it clear what's going on in the UV region
when dealing with graphic arts D50 measurements.

As to it's actual practical impact, I suspect that in the short
term, confusion and lack of understanding will make things
a bit worse.

In the long term the drawback of using something like M1 conditions
for everything, is that it is more sensitive to various inaccuracies
and variations than (say) using FWA/OBE free paper, or using M0 or M2 
I would expect that differences in implementation of the simulated M1 
and approximated M1 illuminants together with any lack of uniformity in FWA/OBE
content of the paper would lead to slightly wider margins of error when 
measurements from different sources, and appearance in different viewing booths.

Another source of confusion is that M1 is not automatically the
right choice for every application. M1 is suitable for viewing
in M1 viewing booths, or in direct sunlight. If the final output is
to be viewed under a lower UV illuminant such as normal fluorescent tubes,
incandescent light, prints under glass, or glass filtered sunlight, then
it may not be as appropriate as M0 or M2 conditions. These lower UV
conditions are quite common, because it's generally not good
for humans to be exposed to D50 levels of UV all the time.

Of course, if the actual viewing situation is fixed and measurable,
then using something like ArgyllCMS's illumread in combination
with FWA compensation creates a specific correction, rather than
being stuck with discrete choices such as M0/M1/M2.

Graeme Gill.

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