Digital BW, The Print

I was curious how much additional smoothness a 5K setup would have over a 3K
setup in the 2200.  Both of the inksets are variants of the approach I
outline at http://home1.gte.net/res09aij/4K+.pdf   This approach is similar
to the Epson K3 approach in that it starts with the standard gray inks --
MK, LK, and LLK.  The toning is done with LM and, in my case, "LLC," which
is a 50% dilution of standard LC.  For the 5K variant, I add 2 more grays:
PK and LLLK (1 part LLK + 2 parts base).  For this test I used a neutral QTR
profile on Premier Art's Matte BW paper.  Note that with the neutral
profile, even the 3K approach always has at least 3 inks firing because the
LM and LLC are always there.  

 

At the black end, the 5K approached used a PK overlap (under printing the
MK).  In the 3K approach I switched to standard cyan color pigment for the
under printing.  This allows one to print a cool MK, which can add some
visual separation in the deep shadows and, in warm interior light, will look
slightly darker for a given density.  As we know from my neutralized Photo
Black (PKN) mixing, cyan (or blue mixed with cyan) can significantly
increase glossy dmax.  With Eboni the results are more modest.

 

To measure smoothness scanned the 21-step test strips with an Epson 1600 dpi
flatbed scanner at 1600 dpi, using RGB mode.  I then used Photoshop's
Histogram standard deviation to measure the relative smoothness.

 

These are the results:

 

%         5K        3K 

 

5%        3         3.8

10%      3.2       4.1

15%      3.8       4.4

30%      4.4       5.4

40%      4.2       5.7

50%      6          5.9

70%      6.1       6.1

80%      5.7       6.9

90%      5.9       6.2

100%    5.7       4.7

 

At 14 inches, I cannot see any difference in the test strips.  With a
magnifying hood at 5 inches, I can see the difference, but it's not dramatic
at all.

 

Of interest, the standard dark cyan in the black was as effective as the PK
for under printing in terms of dmax, and actually resulted in a smoother
100% black.  (Note that I'm not particularly proficient with QTR.  I'm using
the under printing of the black ink primarily to get rid of the small white
lines in the deep blacks that reduce the dmax and smoothness in those areas.
The dmax I'm getting is still not impressive.)

 

At the light end, I noticed that when I removed the super-light LLLK, I
could also reduce the amount of color toners.  As such, the 3K approach is
probably more lightfast, for 2 reasons.  First, the 3K neutral print has
fewer color pigments relative to the more lightfast carbon.  Second, the
more dilute an ink, the faster it fades, all else being equal.  So,
eliminating the super light LLLK probably results in a more lightfast image.


 

At the dark end, eliminating the PK required me to use more color toners
there.  The lighter the carbon ink, the more color is needed to neutralize
it.  However, at the dark end I could have used the same curve and the
darkness of the image would hide the color differences.

 

Also, at the dark end I used standard cyan color for the under printing
instead of a mixed blue for several reasons.  First, cyan pigments are very
lightfast - considerably more so than a mixed blue.  Second, I wanted to
avoid blended inks for large format stability and stay with off the shelf
inks as much as possible.  Third, as one goes deeper into the shadows, the
tones often become too magenta.  Note that even with the pure cyan under
printing (about 15%) the Lab for 100% is 16.8, 1.1, -0.8.  So, the cyan is
not making it green - just cool.  (This could be interesting with the Epson
MK, which is much warmer than Eboni.)  Finally, where I'm going with this is
hopefully a basic hextone version of the Epson K3 inkset that can be run
with either a rip or the Epson driver, including profiling with PFP.  So, I
need relatively normal cross-overs, even if the colors are not where they
were originally intended.

 

Paul

www.PaulRoark.com <http://www.paulroark.com/>  

 

 

 

 



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