Digital BW, The Print

Hello John,

Thanks for the good report.

>Under a loupe, I discovered the "dotless highlights" of the K7 print. 
>However, the K3 print appeared more "luminous" (very slight) in the
>highlights and was preferable in this regard.

This is because K3/ABW, being a "dotty" system, allows some bare
paper, which is quite reflective, to show through between the dots in
the highlights, resulting in a more luminous print.  The dotless
systems get their effect by completely covering the paper with at
least very pale, almost transparent ink in the highlights.  This fills
in between the dots and emulates the continuous tone of emulsion
prints, but covers, and therefore dulls slightly, the paper's
reflective surface.  There's a tradeoff for everything.   

As for the K3 having color inks in the print, that's true, but the K7
also has some color pigments of some sort blended in.  Those inks are
neutralized with something.  We don't know with what, or with how
much, but there's something in there.  I don't know what the
comparative fade resistance is between them, but K3/ABW has some
pretty impressive Wilhelm numbers.  If you look up his 2400 report, 

        http://www.wilhelm-research.com/epson/R2400.html

...keep in mind he has separate results for color prints and ABW
prints, which use much less color inks.  The bottom line: page 3 of
his report rates ABW prints as follows, depending on the paper:

  Framed under normal glass: 110 to >205 years
  Framed under UV glass: 110 to >300 years
  In dark album storage: > 200 years

FWIW, I have a K3/ABW print on my windowsill torture test
(unprotected, with some direct south Florida sunlight every day) for
16 months now, and it's now showing very slight fading only in a
midtone area (the cover strip covers a full range of tones).  
 

>Bottom line: some of you guys must have damn good eyesight!  I don't
>regret trying out the K7 inks, and obviously need to do more
>experimenting, but with results like this why bother?  Please tell me
>what I am missing (if anything).

I don't think you're missing anything.  You have spotted the
significant visual differences in the prints.  Maybe there are some
Wilhelm fade test numbers for K7 out there for comparison.  You should
also compare ink cost and workflow differences.  If 2400 carts are
refilled with MIS K4, the ink cost is significantly reduced.  ABW can
also be used without a RIP (see article #9 at the link below).  A
major difference, of course, is tone control, with K3's variable tone
vs K7's more restricted palette.  K3 will also (with PK) work with
glossy papers and the Silver Rag type papers.  They are both high
quality systems.  It's just a matter of weighing all the differences
and making a choice.    


Regards,
Clayton


Info on black and white digital printing at    
http://www.cjcom.net/digiprnarts.htm