Re: Scanning old Balck and White prints
Re: Scanning old Balck and White prints
- Subject: Re: Scanning old Balck and White prints
- From: neil snape <email@hidden>
- Date: Mon, 12 Feb 2001 22:03:55 +0100
on 2/12/2001 16:21, Joel at email@hidden wrote:
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Mon ami Neil,
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I'm just getting into the whole neutral grey quest with ScanOpen 4.0
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on our Lino Saphir Ultra and Scitex Eversmart Jazz. Tweaking IT8
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generated profiles seems like a reasonable place to go with
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transparency and/or print workflows, but we are increasingly scanning
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watercolour and canvas works. Using our existing IT8 reflective
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profiles generate consistent magenta which varies in intensity
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depending upon which profile being used with whichever paper/canvas
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(ink,oil, acrylic) scanned. I read Hutchinsons Consulting paper
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(1997) on setting hard and fast WPoint/BPoints for the Eversmart, but
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was wondering if you have a scan or PS workflow for generating or
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achieving neutral grey. And I can't seem to find any documentation
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which gives actual Lab values for middle gray. I get varying results
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when I come at it from different directions. Not huge, mind you, but
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enough of a variance not to base a profile edit upon. Lab50a0b0
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renders a (HSB) brightness of 46, while a (HSB) brightness 50 renders
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a L54a0b0. Any hints on target levels? URL's.
I'm can only guess as to the accuracy of the following solutions:
Lab values are easy for a neutral grey i.e.; Lx 0a 0b , getting there from a
non user calibratable scanner (most if not all CCD scanners) is another
thing.
When the profile is built the curves are pulling a little here a little
there maybe a lot just there etc, but in pulling the space around
perceptually for colours and the neutrals. The farther the distance from the
raw rgb the more wild the curves in the profile building. The differences in
the resulting cross over Lab>perceptual will create different rgb values
along the grey wedge EVEN after correctly profiling.
The other aspect lies in the accuracy of the batch measured tdf (text data
file) compared to the actual IT8. My IT8 tx and IT8 rx are both magenta
compared to the tdf file. If you open the tdf in Excel you can compare the
batch Lab values compared to your raw or calibrated scans. This can be
mildly amusing to see how much we'd all like hand measured IT8's.
You can reduce the saturation when you modify the profile in Linocolor 6 and
tweak out the certain grey patches favouring grey balance over colour
balance. Not easy or fun but works. You can also preset your white and dark
end point colour bias here if the profile doesn't 'add up' to your eyes.
ProfileMaker gives you a choice of how you map the grey in the image support
to the media, adapt grey or paper grey. Not an elegant explanation of this
but Henrik can correct me on this.
The profiles from ProfileCity are better balanced than any other profilers
I've seen and you might consider this option.
With today's post by Jon Meyer looks like we'll be moving on into a much
more finely tuned profiling system/method soon.
Hope I've not forgotten too much. You should be getting grey scans within a
couple delta E's when all's set up. And yes the densiometre is the thing to
watch in Lab values on the prescans.