Re: Scanner profiling problem (DT-S1030AI)
Re: Scanner profiling problem (DT-S1030AI)
- Subject: Re: Scanner profiling problem (DT-S1030AI)
- From: Marco Ugolini <email@hidden>
- Date: Fri, 23 Mar 2007 08:53:41 -0700 (GMT-07:00)
In a message dated Mar 23, 2007 2:30 AM, Wolf Faust wrote:
>Looking at the type of faults, lprof also does show the profile
>luminance being too dark by roughly 3. At least from those figures,
>aging of the target and scan settings don't seem to be the cause. I
>need to get some sleep now, maybe I find some more time too look at
>cause tomorrow...
Another thing to keep in mind when creating scanner profiles: the scanner target (the scan of which is then used by the profiling software to create the profile) normally comes with its own generic reference file, which lists ideal Lab numbers for each patch. Due to manufacturing inconsistencies and/or aging of the chart itself, those Lab numbers may turn out to be inaccurate for the actual target one purchases, sometimes by substantial amounts, in which case it's inevitable that the profile itself will be faulty, generating errors like the ones mentioned here.
I see two ways to get around this sort of reference-file imprecision:
1) Buy a Hutchcolor target (<http://www.hutchcolor.com/hct.htm>, each of which comes with its own individual custom reference file, certified to describe the exact appearance of every patch in each of the units being sold);
2) If you use one of "standard" targets instead (IT8, etc), measure each patch yourself using a spectrophotometer, then build a custom reference file: the precision of your profile will be greatly improved, compared to the results you would achieve using the generic reference file. To increase the precision of your custom-built reference chart even further, measure the patches a number of times (three or four, for example), then average the readings.
Marco Ugolini
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