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? Roger 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? Regards, Sam Berry www.satsumatree.co.uk 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? Roger > -----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 is > 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.