Re: Spectros not measuring the same
Re: Spectros not measuring the same
- Subject: Re: Spectros not measuring the same
- From: Simon ONeill <email@hidden>
- Date: Sat, 16 Jan 2010 19:43:14 +0000
Hi Mike,
I have found sometimes that repeated measurements of TC-918 (randomised) charts using my i1Pro (and PM5 Measure tool) can return errors as large as Lab deltaE of 4.0 for a single patch in "strip" mode.
Although it may be unnecessary, I always now compare at least two scans (using Profilemaker Measure tool) and, unless there is a maximum difference of <1.0, I repeat the chart measurement until I get at least two measurement sets which agree. After eliminating single patch errors, typically I find that the maximum deltaE is better than 0.6.
I have not yet discovered why the instrument sometimes messes up (only) a single patch, but have found that remeasuring the offending patch (in patch mode) always gives a repeatable result.
I have seen these single patch errors in "strip-mode" using several different versions of PM5-Measure and also EyeOneMatch. I have only used one i1Pro instrument, but in all other respects the instrument hardware appears to be functioning correctly and consistently, but of course this does not necessarily eliminate a hardware fault in my i1Pro!
Using two instruments adds not only an opportunity for the problem above, but also introduces inter-instrument calibration differences.
My speculation only here (= no direct evidence).... If you are using "strip" mode, differences in the measurement /control software or even operator handling inconsistency could produce discrepancies.
Presumably the other instruments are not UV cut versions.
Simon
On 15 Jan 2010, at 16:40, Mike Stewart wrote:
> I know this is a known issue; but I'm looking for info on the subject. As
> an example; if we measure an ECI2002 Random chart using an i1Pro (D50, 2
> degrees) and then send the exact same printed chart to a printer and they
> in turn use either another i1Pro or another vendors unit we see sometimes
> a rather huge difference in measurements. I've checked that all settings
> have been the same - the difference is the spectro itself. I've read the
> VIGC report and am finding it frustrating to say the least that the
> possibility exists that two spectros from the same manufacturer can
> measure so differently to each other. This plays total havoc when a Pre
> Press house sends proofs to a printer only to have the printer measure the
> same color chart and come back with different readings. What does one tell
> the customer. Thanks in advance - Mike Stewart
>
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