Re: Accuray of EyeOnePro
Re: Accuray of EyeOnePro
- Subject: Re: Accuray of EyeOnePro
- From: Roger Breton <email@hidden>
- Date: Tue, 30 Oct 2007 21:00:05 -0400
Mr. Myers,
Thank you for coming to my rescue!
> OK, I will try to explain why companies are probably not going to give
> you absolute performance metrics.
I may have missed the fact that there are different "practices" in the color
instrument industry with regards to statement of accuracies. It seems that
spectrophotometers are frequently quoted on the basis of inter-instrument
agreement, with respect to BCRA tiles. Seems that way with X-Rite,
Datacolor, Minolta, Techkon and a host of manufacturers. BUT, in the realms
of emissive devices, it seems accepted practices among instrument
manufacturers is to quote accuracy in terms of x,y chromaticity on an
Illuminant A-type of lamp. Even X-Rite does this, to some extent, with the
i1displayII <?>-- look at the i1display brochure (if some one is able to
translate their statement of accuracy with reference to the i1pro, I'll give
you a special place in my heart). So where does that lead us with regards to
the i1pro, I ask you? Nowhere. Sadly. We know what to think of the
instrument's "accuracy" as far as suface color measurement capability is
concerned, through the statement of "inter-instrument agreement". But, to
me, whether it is a Toyota or Ferrari or Spyder or Spectrocam (they still
make them, you know) or a Minolta or a Topcon or a LMT or a Photo-Research,
there has to be some statement of accuracy accompanying the instrument
specifications based on the industry's accepted practives. I don't see why a
less expensive instrument would be free of such disclosure as compared with
the more expensive, supposedly lab-grade instrument (yes, they are
lab-grade, if we are to believe their price sticker). But. as consumers,
we're still interested in knowing the characteristics of what is it we're
buying -- Toyota or Ferrari (I'll take a Camry anytime for my Yaris).
Whether anyone can interpret this gibberish is another matter. I mean, not
anyone can interpret torque when it comes to expressing some aspect of an
engine power but it's there, nevertheless, in black and white, in all car's
brochures.
> The upshot of all this is that the measurement accuracy of a
> spectrometer varies with wavelength, illumination, the type of sensor,
> the temperature of the sensor, the size of the slit, the type and
> shape of diffraction grating, the optics used to manipulate the light
> in the device, and a myriad of other factors. This makes it incredibly
> difficult for a manufacturer to specify their devices in the way
> request by Mr. Breton. Reporting the measurement error as an average
> and maximum delta-E value is about as simply as the error can be
> reduced.
So what? Every manufacturer of emissive devices all use Illuminant A as THE
reference for reporting the accuracy of the instrument -- even though this
information is of no value whatsoever for making an informed judgement about
the capability of an instrument to adequately measure CRTs or LCDs. At
least, the information is there and we can make some informed judgement
about it. I praise Minolta for talking the pain of quoting their emissive
colorimeters's performance with respect with many conditions. They can be
criticised for not quoting other conditions which may interest more
specialized classes of buyers but, at least, they are providing a minimum of
information.
> Even the values reported by Minolta for their emissive device varied
> by intensity, were reported as a variance range and were only reported
> for a single small region of the color space.
Well, yes, "even" Minolta does this. Which, again, goes to show how honest
and upfront they are with their instrument. That way, they don't set any
false expectations in the mind of prospective buyers. I can applaude this
attitude. I don't dispute that performance reporting is a complex exercice.
And I don't want to give the impression that any kind of statement about an
instrument's capabilities are meant to be taken as "absolutes" but it's a
useful basis to work from. To help better identify buyers's needs. Someone
said to me recently that Instrument X from Company Z was amost as accurate
as the i1pro? In emissive mode, he said, and that was judging by the i1pro's
statement of accuracy found in its brochure. Hmmuh. Being the inquisitive
type I am, I started to hunt down for the said accuracy statement in
X-Rite's brchures to be able to compare with Company Z's instrument. But,
much to my dismay, no such statement is to be found in X-Rite's brochure?
Darn. I simply could not substantiate the claim this other person was making
about the i1pro, as much as I like the i1pro. It's like a Toyota without
complete specifications.
Regards,
Roger Breton
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