Digital BW, The Print

I think reciprocity failure  is the key to why Cone has consistently refused
to put "years" on longevity data.  It is a really foolish thing to
do...particularly when we want these things to last for a 100 years...there
is absolutely no way to give a valid 100 year projection...until we have
prints that have been around that long.  In the end the best we can hope for
is what Cone has given us relative testing, with full published results done
by a reputable testing group (RIT)...and hopefully more comparative testing
done by RIT in the future.  I've said this many times before...and I'll say
it again...it would also be nice to see some archivally printed silver
prints included in this testing as well...now whose processing and what
darkroom conditions is a big topic for debate...but any data along those
lines would be a help at this point.

Robert

On 11/9/02 9:09 AM, "hjswim2@..." <hjswim2@...> wrote:

> Paul: <SNIP ... While we're on the subject, note the extent to which
> "reciprocity failure" of the accelerated tests gets more serious as the
> illumination level
> increases.  ... In short, if one tries to project "years of display" without
> considering reciprocity failure, the exaggeration of the predicted life could
> be huge.>
> 
> Yes, indeed. Reciprocity failure is the Achilles Heel of accelerated testing,
> IMO, significantly *underestimating* fading. And what's interesting is that
> Henry Wilhelm has known this all along, at least since the mid-'70s. In fact,
> he devotes a whole table to it in his 1993 book. Yet, the latest published
> testing results from Wilhelm all assume a reciprocity failure of ZERO. Not
> quite sure why. Supposedly, his new test methodology takes this into account
> somehow. We'll see.
> 
> Harald Johnson
> author, "Mastering Digital Printing"
> DP&I.com ( http://www.dpandi.com )