Re: Fingerprinting a Sheetfed Press
Re: Fingerprinting a Sheetfed Press
- Subject: Re: Fingerprinting a Sheetfed Press
- From: Roberto Michelena <email@hidden>
- Date: Thu, 15 Sep 2005 09:16:48 -0500
Matt,
Standards are evolving faster nowadays than they did in the last 10 years.
"old" standards were based on two factors: SID (solid ink density) and
TVI (Tone Value Increase, aka total dot gain).
SID measured either wet or dry, status T (USA) or Status E (Europe);
dot gain measured at 50% (USA) or at 40% and 60% (Europe).
Current ISO standards departed from density as an indicator, and
instead specify colorimetric targets for the solid colors (Lab). Lab
values for secondary colors are also specified but not mandatory,
however highly recommended. TVI or dot gain is specified as a curve
shape, not only "value at 50%". And paper colorimetry is also
specified, defining several paper types.
Newer trends that are likely to be the basis of GraCol v7, focus on
gray balance as the first target to be matched, and then dot gain
curves as manipulable via software to meet the intended targets. The
function that SID or colorimetry of solids will have in GraCol v7 is
not yet clear to me.
In both ISO and Gracol v7, inks are specified as compliant to another
ISO standard defining their color (within a tolerance).
I would totally forgo, nowadays, density-based standards such as SWOP,
that leave so much variability unaccounted for.
As Gracol v7 is not yet out, and is still kind of experimental, I
would rather choose ISO 12647 as the standard to match, making the
adequate correction for dot gain that results from using negative-film
workflow (if doing film).
-- Roberto Michelena
Infinitek
Lima, Peru
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