Digital BW, The Print

Ernst,

What I did to find the best dmax was, in the IJC ink curves graph, have the
UC MK (when dealing with the OEM inkset) be a horizontal line at the level
of 250 of the 255 scale.  (In this case, more is darker.  This translates
into ink load 25 of a maximum 26 for that system.)  Then I ran the cyan
curve at a diagonal line from 0 to 255.  I printed a test strip for
linearization and inspected the output.  The best dmax with a clearly
descending density below it was at patch 4 of 26.  So, it took very little
cyan laid on top of wet UC MK to increase the dmax noticeably over what this
particular system was able to do with just UC MK.  The IJC dmax with just MK
was about the same as the Epson driver.  Perhaps other rips can do better
with just mk such that this approach is just not needed or effective.


Paul
www.PaulRoark.com 


> -----Original Message-----
> From: Ernst Dinkla [mailto:E.Dinkla@...]
> Sent: Friday, March 18, 2005 6:09 AM
> To: DigitalBlackandWhiteThePrint@yahoogroups.com
> Subject: [Digital BW] Cyan overcoat, Cyan underlay for Black... was Glop
> etc
> 
> 
> Paul Roark wrote:
> 
> >>> Have you tried a dark cyan overcoat?
> >>>
> >>>
> >>>
> >
> >
> >
> >>I will try that. But an overcoat of cyan pigment on a black pigment
> >>layer isn't producing a black dye layer though.
> >>
> >>
> >
> >True, it's not a dye.  But if it is truly transparent, then it relies on
> the
> >reflectance of the  underlying substrate -- usually paper.  Here,
> however,
> >that substrate is carbon.  So, its absorbency, the way a subtractive,
> >transparent color works, takes out only certain colors of the underlying,
> >reflective substrate.  Carbon is warm, so the cyan is absorbing the reds
> of
> >that warmth.  The cyan part of the carbon reflection will come right back
> >through, but there isn't much of that.
> >
> >I guess the question is, in part, how transparent the cyan really is.
> >
> >
> >
> >
> >
> >>One of my concerns with colored overcoatings is that they may increase
> >>metamerism.
> >>
> >>
> >
> >What I saw was so dark if there is some it's not of much consequence.
> >
> >Only one way to see.
> >
> >
> Paul,
> 
> No positive results.
> 
> I have printed some proofs with the Epson 10K, WasatchSoftRip, MIS 7600
> inks (including Eboni black) on HPR. Spectrocam Status T measurements.
> 
> The RIP was unlinearised, uncalibrated etc for this task, no need for
> that either. Straight CMYK fed it gives straight CMYK output. A square
> with strips descending  from 100% black, 99%, 94%, up to 66% black, next
> to one another. First two prints of that. Forced dried and after 30
> minutes a similar Cyan square printed on the black but 90 degrees
> turned. The other black square was over printed with the Light Cyan
> steps = 50% > 33% C.
> 
> The results, less visual blackness, a heavy magenta-aubergine sheen and
> a drop in Dmax of the best black strip (94%) from 1.747  to 1.54 for the
> 100% cyan overcoat to 1.65 for the Lightest Cyan strip.
> 
> The other way around with Cyan first and black overcoat delivered a drop
> in Dmax of about 0.06 for the heaviest Cyan underlay and 0.02 for the
> lightest Cyan underlay. So no gain there either. Visually a bit bluer
> and lighter, which seems to increase in time, not much metamerism. I
> don't think I will measure them again, there's nothing to win there.
> 
> Given the weaving of the Epson head and the color print order the truth
> will be somewhere in between when this is done in one printrun.
> 
> This shows how much pigment inks reflect light. It may be different for
> another inkset.
> 
> There's one thing we didn't discuss on the differences between dye and
> pigment inks. The dye ink will be more transparent but still have more
> coloring power, I don't think one can put a too heavy load of dye in an
> inkjet ink, it will still print. With pigment inks we are at the edge of
> consistency in inkjet printing, pigment settling and piezo pump capacity
> etc considered. The coloring power of the dye will result in a darker
> coating from the top to the bottom. Less reflection than with pigments
> and heavier filtering inwards.
> 
> Ernst
> 
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> 
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