longevity and accuracy of scan charts
longevity and accuracy of scan charts
- Subject: longevity and accuracy of scan charts
- From: drdot <email@hidden>
- Date: Tue, 30 Apr 2002 11:34:32 -0700
Since I posted last question on this list about IT8 Scanner calibration
charts, I have received some information that may be of some use to the
list. Since watching charts fade is not a common practice. Digging up this
information was tough. It seemed odd to me that since scanner calibration
is one of the corner stones of modern color management. Why do we trust the
stability of film emulsion that is designed to react to light and oxidation
as its method of manufacturing color?
Don Hutcheson contributed the best information that I have received so far.
Some of this is elementary for the advanced but it is good to see someone
at least point toward a loose schedule and reasoning for auditing them for
longevity and accuracy. I feel this is better then just assuming they are
OK for one year (or any other assumed amount of time) without questioning
the target.
Don Hutcheson Said
----
If you take care to minimize exposure to excessive light intensities or
duration's, you should easily get a year or more of first-grade use out of
a Fujichrome HCT, even with heavy use. Just avoid leaving it on a light box
any longer than necessary. Ektachrome targets will fade somewhat quicker,
but I have never done a time/intensity fade test. You might want to contact
Henry Wilhelm who makes a living out of fade-testing.
Instead of buying a new target every year, I suggest you have your HCT
re-measured after every 12 months of hard use. The result may show no
significant error but will automatically regenerate the target's value for
another twelve month period.
If there is no measurable error after the first twelve months you could
extend the period to two years, but re-measuring is relatively cheap -
about $200 from your original dealer, and a good way to keep the target
valid.
Ektacolor, Fujicolor and Kodacolor are negative films, for which there is
no logical concept of profiling. Hence there is no C-neg HCT or IT8 target.
The good news is that on most drum scanners the Fujichrome target matches
other E-6 chemistry films such as Ektachrome and Agfachrome so well you are
hard-pressed to see any difference. The odd emulsion is Kodachrome, which
uses K-14 chemistry and scans much bluer than E-6 films.
----
Thanks and hope this was a worth while read for someone
Sam Landry
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