Digital BW, The Print

pr_roark wrote:
> Ernst,
> 
>> ... Right now I get better Dmax
>> with the HP Vivera on Photorag than I got with MIS Eboni.
>> 1.67 versus 1.77 D. ...
> 
> Is the HP black a 100% pigment ink?

A carbon pigment. There must be another colorant in/on the 
pigment particle, in the encapsulation or the ink media as 
carbon itself isn't neutral. Could be another trick but in 
the end it behaves as a colorant and could shift test 
results. The inks test well in fade tests though both for 
color and B&W with light and ozone fading counted. The test 
results have been updated recently by Wilhelm.

http://www.wilhelm-research.com/hp/WIR_HP_Z3100_2007_12_28.pdf

another test result for color only:

http://digitalkamera.image-engineering.de/downloads/Haltbarkeit_Papiere-Cofo.pdf

There are some English articles on the same site.
Given the high resistance of all the colors to the tests I 
think they will have a good neutraliser on the grey inks too.

> 
> Apparently the HP machines use 4 inks for the 100% black. These include
> the light gray inks.   The use of all these inks at once is said to be
> what is behind the high matte paper dmax.  This is certainly different
> than my experience with pigment inks in Epson printers.  The only time
> I've seen addition of an LK to the 100% spot raise the dmax is when the
> K is not covering well.  If the MK is covering well, I almost always see
> a decrease in dmax when a lower load ink is added to the mix.

The quad set is only used in 2 media presets for matte 
papers, the other matte papers and the gloss depend on 3 
inks only. I have used two different ones (3 and 4 inks both 
MK) for Photorag and there was a Dmax difference, the quad 
was better. HP's gives different inkloads for the two too: 
42 versus 60 but call that ink limiting and now I doubt it 
is what we call ink limiting. I thought that the PK would be 
used in the quad to offer that higher Dmax but I'm no longer 
sure that that is the case since I observed that the Z3100 
PK doesn't deliver that much density on matte papers and 
could cooperate well as a second quad ink for that reason 
alone and not as an addition to boost the MK Dmax. The ink 
load term then corresponds better with an additional use of 
PK and and less MK in the lighter shadows. The Quad media 
presets are only used on heavier stock, there's for example 
a split between Photorag above 250 grams and below (HP uses 
other names in the media presets). The PK is squirted as a 4 
picoliter droplet and the MK as a 6 picoliter droplet, I 
guess the last together with the latest dithering/weaving 
methods is the reason for the high Dmax on matte papers. A 
real difference in inklimit on the black between the Kkk and 
Kkkk on top of that.  The Dmax is not higher than the K3 on 
some Epson matte papers as I have seen quotes of 1.77 D for 
that combination too. Whether they both end equal with real 
neutral black prints is something else. On plain HM Photorag 
I didn't get better Dmax with any other inkset before.

> 
> I believe Wilhelm tests do not pick up a hybrid black, which my testing
> indicates included the original Eposn 7500 Archival K.  So, a good
> Wilhelm rating may not be a guarantee that the black ink is not a
> hybrid.

True but as written both B&W and color test extremely well 
with Vivera pigment if compared to the other manufacturers. 
The Epson 7500 Archival (with a universal gloss/matte K) was 
the first Epson pigment ink for their own brand of printers 
with lots of metamerism problems and the black not high in 
density on matte papers. Since then there have been 2 new 
Epson pigment inks with changes on the black inks.  Epson 
went for straight carbon so one needs compensation colors to 
get neutral prints. HP introduced a neutral K range in the 
Vivera pigment inks for the B9180, Z2100, Z3100 and Z6100. 
If the test institutes use the plain B&W mode of the drivers 
and do not seek neutrality in the test targets then at least 
HP sticks its head more out than Epson.

Neutrality shifts during fading are checked by Image 
Engineering on some density numbers, in fact the majority of 
the criteria is related to neutrality, see:

http://digitalkamera.image-engineering.de/downloads/printer_test_white_paper1.0.pdf

I guess Wilhelm must have similar methods.
There's a note under the test criteria list where they 
explain that the densities measured may be altered in the 
future and the density loss may be changed from percentage 
to Delta E. The ISO is more than 10 years in draft now and I 
understand that this is one of the issues that keeps the 
discussion going. Another opinion on what to test and 
measure is what Mark McCormick voices here and testing will 
start soon as I understand it:

http://forums.dpreview.com/forums/read.asp?forum=1003&message=26244617
http://www.aardenburg-imaging.com/digitalprintresearch.html

He has a list where the new Fiber papers are included, an 
omission in the latest testing results. Wilhelm has the 
Epson Exhibition Fiber also on the list to do though.

Wilhelm, McCormick and Wueller, all three are or were on the 
ISO committee. There may not be a universal testing method 
yet but with more labs around with some credibility  (WR, 
IE, RIT, Fogra, McC)  that use different methods it may even 
be better than one standard with some flaws

-- 
Met vriendelijke groeten, Ernst


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