[argyllcms] Re: ColorMunki measurement drift

  • From: Roger Breton <graxx@xxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sat, 02 Oct 2010 14:37:33 -0400

What a discussion. I don?t think you are missing anything Sam. 


I once hired the NRC to characterize the colorimetric response of a Minolta
CS-1000 to a Minolta CS-100, based on an Eizo CG21 LCD CCFL monitor, a few
years ago. I?d have to dig out the report I was sent by the PhD who took my
assignment but, if memory serves, using Matlab and an advanced kind of
linear algebra my humble college math won?t allow me to comprehend fully, I
believe the difference between the two instrument?s readings, after
mathematically correcting the CS-100 for the CS-1000, was in the order of a
delta E. 


I?m told that commercial spectroradiometers is a 3% accuracy business? 




From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-bounce@xxxxxxxxxxxxx]
On Behalf Of Sam Berry
Sent: 2 octobre 2010 09:45
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Re: ColorMunki measurement drift


Whilst I appreciate that there is a lot of care that goes into the
calibration of these instruments, and that I have no direct experience with
such a calibre of instrument, the uncertainty levels you refer to are surely
quoted measuring illuminant 'A'. I cannot find any spectroradiometer
specifications which give typical uncertainties when measuring typical
display spectra, but I would be very surprised to find that they are up to
such similarly high standards. In the absence of a published spec, it seems
unfair to assume. You may certainly have more practical experience that me,
however, but I doubt that many people have access to a lab with multiple
spectros.  I would hope that repeatability a good order of magnitude better
than shown by the colormunki here was attainable though.

Although I cannot find the spec of the Pr-704 online, the Pr-705's accuracy
is listed as +-0.0015x +-0.001y. According to my calculations, this results
in an error disc approximately 1.3deltaE in diameter, for a single
instrument measuring a continuous and known spectrum. I would be extremely
surprised to find different manufacturer's lab grade spectros agreeing
within 2deltaE of each other on a spectra such as an LED's, or perhaps a
CCFL such as in the NEC above. Only the single-instrument repeatability
specs are under 1DE. Am I mis-reading something?

Sam Berry

On 2 October 2010 12:42, Roger Breton <graxx@xxxxxxxxxxxx> wrote:

The lamps these instruments are calibrated against are either PTB, NIST or
NRC traceable, within their respective uncertainty budgets, which usually
translate into fractions of delta Es. Still not good enough for you?


> -----Original Message-----
> From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-

> bounce@xxxxxxxxxxxxx] On Behalf Of edmund ronald
> Sent: 2 octobre 2010 04:50
> To: argyllcms@xxxxxxxxxxxxx
> Subject: [argyllcms] Re: ColorMunki measurement drift
> I am afraid there is not really "ONE" reference instrument at this time -
> depending on whether you chose PhotoResearch or Minolta or something
> else you will get different "references". The best one can really hope for
> that one manufacturer's instruments match between each other.
>  That's assuming they are good enough to measure the same at different
> points in time.
> Edmund
> On Sat, Oct 2, 2010 at 3:53 AM, Roger Breton <graxx@xxxxxxxxxxxx> wrote:
> > Among all the instruments I enumerated, the PR-704 can be a reference
> > instrument ? no offence / Roger
> >
> >
> >
> > From: argyllcms-bounce@xxxxxxxxxxxxx
> > [mailto:argyllcms-bounce@xxxxxxxxxxxxx]
> > On Behalf Of János, Tóth F.
> > Sent: 1 octobre 2010 21:02
> >
> > To: argyllcms@xxxxxxxxxxxxx
> > Subject: [argyllcms] Re: ColorMunki measurement drift
> >
> >
> >
> > Well, I think we should compare each of those instruments to a much
> > better reference instrument (or a reference light source), but not
> > between each others. I think it can't tell anything. They will be
> > closer to or further from the true but randomly, so you can't tell.


Other related posts: