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Subject: Conservation display ratings for digital print media

Conservation display ratings for digital print media

From: Mark McCormick-Goodhart <mark<-at->
Date: Wednesday, January 21, 2009
I have recently implemented a new method for rating the
lightfastness of Digital print media. For lack of a better name, I
call the new test results  "Conservation Display" ratings. The basic
premise was to create a new test and set of criteria for digital
print media that offers guidance on the allowable light exposure
dose where prints still remain in visually good to excellent
condition. In the absence of an ISO or other standards group
specification on the lightfastness of photographs, a rating method
better suited to the needs of the museums and archives community is
somewhat overdue.  The new conservation display rating clearly
differs from industry-sponsored consumer photo "display life"
ratings which are typically derived from exposure doses that allow
the media to reach easily noticeable and often objectionable levels
of fade.

At the "end" of test, the conservation display rated prints have
small but measurable light-induced changes.  However, the changes
have been constrained to amounts that are not easy to visually pick
out in a complex field of colors (e.g., a color photographic image),
so the prints remain in very good to excellent visual condition.
There are other important attributes of conservation display ratings
as well including the fact that the test results report an exposure
range rather than single-value number, and they are expressed in
megalux- hours rather than being carried through to nominal "years
on display" figures (which I've long felt grossly oversimplify the
light fading issue in the minds of consumers).

The conservation display ratings are also derived using the I*
metric which is a colorimetric algorithm for color (hue and chroma)
and tonal (lightness and contrast) accuracy.  It differs from delta
E color difference models in key areas that are really important
when dealing with real images as opposed to just two solid color
patches being observed side-by-side.  The I* metric was published in
the NIP 20 conference proceedings of the Society for Imaging Science
and Technology in 2004.  It has been the cornerstone of several
years of research carried out with colleagues at Wilhelm Imaging
Research and also here at Aardenburg-Imaging and Archives. The I*
metric is open source... anyone can use it.  The technology can also
be tailored to give image content-specific scores which would be
useful documentation for museums and galleries purchasing or selling
valuable works from contemporary artists and printmakers working
digitally.  Inquiries about real world print monitoring and
evaluation are welcome.

You can find papers on the I* metric plus an overview of the
conservation display rating method (as well as some test results
with public access) on my website.


There is also information about the I* metric on the Wilhelm Imaging
Research website:


Mark McCormick-Goodhart
Director, Aardenburg Imaging and Archives
Lee, Massachusetts

                  Conservation DistList Instance 22:41
                Distributed: Wednesday, January 21, 2009
                       Message Id: cdl-22-41-001
Received on Wednesday, 21 January, 2009

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