Re: Spectrophotometer accuracy
Re: Spectrophotometer accuracy
- Subject: Re: Spectrophotometer accuracy
- From: Roger Breton <email@hidden>
- Date: Thu, 25 Aug 2005 19:52:32 -0400
>> Is there an ³absolute² method to determining spectrophotometer accuracy?
>> i.e. is there a calibrated standard available with known LAB values?
>> And just how accurate should spectrophotometers be (+/- how much)?
>> How long is the white calibration tile good for?
>>
>> Here¹s the situation: I have two spectrophotometers - a GretagMacbeth
>> Spectrolino (with the attached UV-cut filter) and a GretagMacbeth EyeOne Pro
>> w/ UV-cut.
>
> Here is a link to a paper that describes how you can improve inter-instrument
> agreement for your two devices. If you follow up on many of the entries in the
> references at the end, you will also find some great information on how to
> determine the precision and accuracy of your instruments. As already
> mentioned, however, you will need BCRA tiles, or similar, to do this. If you
> can't purchase them, perhaps there would be someone who would lend (or rent)
> them to you.
>
> <http://www.npes.org/standards/cgats/White Paper_Inter-Instrument Agreemen
> t.pdf>
>
> Hope that helps.
>
> Ken Fleisher
Dear Ken and Michael,
The White Paper you refer to is certainly to be regarded as landmark in
reconciling readings from otherwise irreconcilable instruments. It's as far
reaching as it can get IMO. But the math required to implement it not for
the faint of heart. But to top it off, Dr. Rich extremely rich sample set is
drawn from materials most of us would never have the financial means to
afford, let alone source. Yes, that makes his results all the more bullet
proof but is that a methodology really at the reach of mere color mortals
like many readers on this list? I'd wish someone would turn a procedure like
his into a commercial product. Unless someone is willing to step in and
guide us, step by step, in an application like Excel, and help develop
regression coefficients? I'm all ears.
As for BCRA tiles, I'm getting a basic set calibrated for 0/45 geometry here
and it's costing me two arms and two legs. But at least, once and for all,
I'll know which of my instruments is lying to me -- in absolute terms. And
let me state that this will only be valid for non-fluorescent samples.
Color is not simple ;-)
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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