Digital BW, The Print

Walt,

> ... I too am uncomfortable, in principle, with the use of 
> pure color inks in BW printing (as with the K3s).

I'd still like to see some double blind tests to see if people can sense the
difference visually.  I'm a bit skeptical about that.  So, if there had been
no significant fading difference, I might well have just gone with the
straight k3 approach.  There is no doubt that having color available
occasionally is useful even for strictly B&W guys like me.

>  What I wanted was a sense of the real
> world significance of a L* 0.70 difference in fade given your
> light/time exposure.
> 
> This question arises for me partly because such an absolute
> difference is very small...

Yes, all of absolute fade amounts were small.  The results are only
significant if put into the context of the relative fade rates.  There, in
the extreme case of the ABW mode k3 print v. the MIS UT dedicated B&W test
strip, there was a 3x difference.  On the other hand, the significance of
this fade rate difference depends on additional assumptions, such as whether
the rates we see in initial fading will continue.  So, there are some
variables here that are simply not completely known.  For my own purposes, I
think the results are significant, but I would never go so far as to say my
tests "prove" that the dedicated B&W inksets are three times as lightfast.
I've simply seen enough evidence, including but not limited to just this
fade test, that I think it's now worth my time to take the next step.

 
> ... I don't know what you estimate your exposure to be 
> relative to the total display life of a print.
> Is the difference you report just the "beginning of the
> story,"...

Clearly what I'm reporting is just the beginning of the story.  Based on my
best measure of how bright the light is, I've tried to give some equivalence
to "Wilhelm years" of display.  However, not only is my equivalence a rough
estimate, but also I'm not sure how many really trust that the "years"
Wilhelm uses are realistic.  (Then again Kodak assumes even less light
exposure for its calculations.)

Put in the setting of traditional collector's skepticism about inkjet
technology, I'm just trying to get the best performance I can relative the
Epson pigments, which Epson will promote using Wilhelm data.  I'll then
simply do the best I can to leverage off those numbers, trying to avoid the
issue of what the "life" of a print is.


> Incidentally, what are you measuring?

I use a 50% patch.  I do have some additional test strips in the fader with
a range of densities.  The 50% patch, however, seems to be representative of
the midtones, and the black patch is a separate ink.  In the past I've
tested the black inks, and the MIS and Epson versions are roughly equal and
very good -- being basically carbon (not the PKN).  A BO print is about as
good as it gets in this respect, which is one reason Clayton and some others
are such fans of that approach.


Paul
www.PaulRoark.com