Digital BW, The Print

Hi, I am fairly new at this forum. I downloaded QTR and have run some 
tests and have been pleased with the neutral tones I can get as well 
as the absence of metamerism. However, I am having trouble getting the 
deep blacks I got when simply printing through PS CS and the Epson 
2200 driver. I have played with the sliders in the gui and I have also 
tried adjusting the image itself to make sure I have absolute blacks, 
but I have not found the answer to the problem. It's not that big of 
deal for some subjects, but when there are large areas of black within 
the image, the blacks themselves become part of beauty of the image. 
What am I doing wrong? Are you able to get the same rich blacks with 
the QTR or is it a function of not mixing colors to create a black as 
opposed to the just the ink in the black cartridge. I am using the 
papers that are already calibrated in the program and UC inks, with 
matte black. (I am printing on Entrada, and Epson Watercolor)

Any help would be greatly appreciated.

Michael Fulks

Hello Michael,

>I downloaded QTR...However, I am having trouble getting the 
>deep blacks I got when simply printing through PS CS and the Epson 
>2200 driver. I have played with the sliders in the gui and I have
also 
>tried adjusting the image itself to make sure I have absolute
blacks, 
>but I have not found the answer to the problem. 
>Any help would be greatly appreciated.

The blackest possible print area can only be achieved when there is
100% coverage by only the K ink.  Many systems that blend inks often
mix something else along with the K, even in the lowest zones.  This
effectively reduces the dmax.  I see this with UT7 using sliders,
where it can't match BO dmax.  So you need to adjust the curves to
ensure there is only K down there.  However, I think there is more to
it than just eliminating other inks.

In a BO print the visible paper white specks disappear at around 95%,
yet the Epson driver is still able to achieve gradations between 95
and 100%.  I assume it's because even though the dots are overlapping
at that point, the dot centers are continually spaced closer together
as it approaches 100%.  This means that the amount of ink laid down
increases and affects visual density, even though there is full
coverage of the paper at 95%.

So when adjusting blending curves, seems like the challenge would be
not only when to eliminate other inks, but also how to achieve the 
continuous gradation from that point on with only K ink.

As to where to cut out the other inks, seems to me that any dilution
of pure K is going to weaken the visual affect, so eliminate other
inks at the earliest possible place.  Since the grainy look of a BO
print fully disappears around 80 or 85%, that should be the ideal
place. That would equal BO's dmax and beautiful intensity in the lower
zones, one of its strong points, yet still have a non-grainy print -
the best of both worlds.  This of course assumes the ability to get
the pure K gradation like the Epson driver does.

I would be very interested to hear from QTR/IJC users if this is
possible.  Is anyone doing this?

Regards,
Clayton


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

Clayton, 

...

> The blackest possible print area can only be achieved when there is
> 100% coverage by only the K ink.

With a rip I can get a better dmax with cyan added to the black.  The Epson
driver can't do this, and the old printers that under-print the black ended
up with a lower dmax.


> Many systems that blend inks often
> mix something else along with the K, even in the lowest zones.  This
> effectively reduces the dmax.

Usually, but not always.  The UC MK with UC cyan added is the most dramatic
exception I've seen.   With UT7, a little dark cool gray added to the Eboni
can also increase dmax a bit. 


>  I see this with UT7 using sliders, where it can't match BO dmax.

The UT7 sliders do not underprint the 100% black with gray inks.

I just printed 100% black patches with UT7, Eboni, 2200, and EEM.  With the
sliders the dmax is 1.66.  With black only the dmax is 1.66.  There is no
difference.

What we've discussed in the past is that the various approaches differ with
respect to how much contrast exists between 100% and 95%.  With curves, this
is totally controllable.  With the sliders, there is less flexibility.  The
image has to be adjusted in Photoshop to fit the printing characteristics --
which is true in any case.

Paul
www.PaulRoark.com

With QTR you can just have pure black at 100%.  You can also control the ink
limit at that level.  I do think there is an issue with Gimp's dither not
really working at 100% ink load (at least on my 2100) but you need to be
careful making a comparison with the Epson driver.  You don't know what %
ink the Epson driver lays down at 100% black - it is not visible to you nor
definable by you.  It could be inherently regulated at 90%, for example.

In any case, I posted a while ago the results of my QTR ICC workflow, Epson
"colour" driver and Epson BO driver comparison.  They can be found here:

http://homepage.mac.com/stevekale/stevekale2/FileSharing37.html

I was using the canned QTR profiles for Epson UC inks, an Epson 2100 and
matte paper with MIS' UC equivalent inks (so eboni in the K slot).  The
Epson colour profile was my Eye One-generated EEM profile which was profiled
after spraying the test chart with Lascaux fixitive.  The QTR curve was
linearised after spraying with Lascaux fixative. I did not spray for this
test - all results are without spray.  QTR and the Epson colour driver
achieve identical dMax (for all intents and purposes) and BO exceeds them by
a small margin.  BO has the poorest UNADJUSTED (no print curve) reproduction
of the step wedge image, especially when the gamma is set at 1.8 which is
not surprising as it is way off the gamma of Lab (the step wedge) which is
best approximated by 2.2.  What I was a bit surprised about was the extent
of difference between the Epson colour profile and QTR - remember we are
just measuring density or L(uminance) here.  Both QTR and Epson colour used
perceptual rendering intent to map to a print space with the same paper
white and ink black.  If the Epson profile were linear I would expect the
two to be right on top of each other - although I was using the canned QTR
profile and not one linearised for my printer and that will be a
contributing factor.  Note that QTR produced the most accurate
representation of the midtones in the test.

> From: Clayton Jones <cj@...>

> 
> The blackest possible print area can only be achieved when there is
> 100% coverage by only the K ink.  Many systems that blend inks often
> mix something else along with the K, even in the lowest zones.  This
> effectively reduces the dmax.  I see this with UT7 using sliders,
> where it can't match BO dmax.  So you need to adjust the curves to
> ensure there is only K down there.  However, I think there is more to
> it than just eliminating other inks.
> 
> In a BO print the visible paper white specks disappear at around 95%,
> yet the Epson driver is still able to achieve gradations between 95
> and 100%.  I assume it's because even though the dots are overlapping
> at that point, the dot centers are continually spaced closer together
> as it approaches 100%.  This means that the amount of ink laid down
> increases and affects visual density, even though there is full
> coverage of the paper at 95%.
> 
> So when adjusting blending curves, seems like the challenge would be
> not only when to eliminate other inks, but also how to achieve the
> continuous gradation from that point on with only K ink.
> 
> As to where to cut out the other inks, seems to me that any dilution
> of pure K is going to weaken the visual affect, so eliminate other
> inks at the earliest possible place.  Since the grainy look of a BO
> print fully disappears around 80 or 85%, that should be the ideal
> place. That would equal BO's dmax and beautiful intensity in the lower
> zones, one of its strong points, yet still have a non-grainy print -
> the best of both worlds.  This of course assumes the ability to get
> the pure K gradation like the Epson driver does.
> 
> I would be very interested to hear from QTR/IJC users if this is
> possible.  Is anyone doing this?
> 
> Regards,
> Clayton
>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Clayton Jones" 
<cj@c...> wrote:
>...
> The blackest possible print area can only be achieved when there is
> 100% coverage by only the K ink.
>...

I haven't been able to find a general rule for whether or not it
is advantageous to add another ink to the black without adding a 
second black: it seems to depend on the inkset and the paper. Here, 
as an example, are some of my results from Sundance Septone inks in a 
2200, with IJC/OPM, and Clayton Jones' BO method with the Epson 
driver:

HPR: no increase over BO DMax by mixing dark grey with the black, no 
decrease either.

Entrada Fine Art: slight loss of DMax (0.01 to 0.03) by mixing 
neutral dark grey with the black, no change or slight increase with 
warm dark grey.

Merlin Photo: increase of about 0.1 in DMax by mixing neutral dark 
grey with the black – I have the feeling that the paper can
handle a lot of ink.

Ilford Galerie Smooth Glossy; Kokopelli Photo Gloss: the results seem 
to depend on the nature of the subsequent coating, so the number of 
variations is large - black ink amount, overlay ink colour(s) and 
amount(s), coating - and I haven't drawn clear conclusions yet. I 
have the impression that some coatings (eg rolled-on water-based 
varnish) achieve significant increases in DMax (typically 0.6 to 0.7 
to give a final DMax of around 2.6) by allowing some unabsorbed ink 
to migrate a very short distance upwards into the coating, creating 
an extremely thin layer of black varnish. If I begin by misting the 
surface with a solvent-based spray I don't see the same increase
in DMax – only 0.1 to 0.3. I need to look into this more deeply,
but 
that is my favourite explanation at the moment.

The coating methods that produce a large increase in DMax do not show 
much improvement by adding dark grey, but the coatings that produce 
little increase in DMax do show some benefit when dark grey is added.

These results do not contradict Clayton Jones' statement: a greater 
increase in DMax could be possible by adding a second black instead 
of dark grey, of course.

Best, Helen

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "helen_bach2003"
<helenbach@h...> wrote:
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Clayton Jones" 
> <cj@c...> wrote:
> >...
> > The blackest possible print area can only be achieved when there is
> > 100% coverage by only the K ink.
> >...
> 
> I haven't been able to find a general rule for whether or not it
> is advantageous to add another ink to the black without adding a 
> second black: it seems to depend on the inkset and the paper

Exactly, and that has always been the case.
Tyler

Paul, Steve, Helen, Tyler,

>>I haven't been able to find a general rule for whether or not it
>>is advantageous to add another ink to the black without adding a 
>>second black: it seems to depend on the inkset and the paper
> 
>Exactly, and that has always been the case.

Thanks for all the good replies.  Taken together they would seem to go
along with my observation of the BO prints acheiving continuing
gradation past the point where full coverage begins.  Perhaps dmax can
be increased with greater ink load (assuming the 2nd ink isn't too
light) up to a point.   If some papers can handle more ink than others
before that point is reached, it would explain the seemingly
conflicting results reported here. All very interesting, thanks.  

Regards,
Clayton


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

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Clayton Jones"
<cj@c...> wrote:
...
> Thanks for all the good replies.  Taken together they would seem to go
> along with my observation of the BO prints acheiving continuing
> gradation past the point where full coverage begins.

Clayton, I'm not sure where this idea of full coverage came from. It's
mostly mentioned here on this list. Anywhere else, it's all about
density measurements, whatever the "coverage".
It's no suprise to me that density can increase beyond the full
coverage point. I'm sure none of these inks are truly opaque.
If there was considerable dry time between passes, you'd see even
higher densities.
Consider those working with double pass printing, higher densities.
Tyler

Hello Tyler,

>Clayton, I'm not sure where this idea of full coverage came from. 

It was just my observation of BO prints that, viewed with a loupe, the
specs of paper white disappear completely at around 95%, meaning that
the dots are close enough to fully overlap.  I was making the point
that even though full coverage begins at 95%, there is still
increasing visual density as the ramp moves toward 100%.  I assume
this is due to the dots being continually placed closer together,
which would mean greater overlap, which means more ink is being laid
down.  This would seem to support the idea that increasing ink load
increases visual density.  It doesn't have any significance beyond
that.  It's just the point at which there is no more uninked paper
showing.

Regards,
Clayton


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

Clayton, didn't mean to jump on you in particular, and I agree completely.
Tyler

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Clayton Jones"
<cj@c...> wrote:

> 
> Hello Tyler,
> 
> >Clayton, I'm not sure where this idea of full coverage came from. 
> 
> It was just my observation of BO prints that, viewed with a loupe, the
> specs of paper white disappear completely at around 95%, meaning that
> the dots are close enough to fully overlap.  I was making the point
> that even though full coverage begins at 95%, there is still
> increasing visual density as the ramp moves toward 100%.  I assume
> this is due to the dots being continually placed closer together,
> which would mean greater overlap, which means more ink is being laid
> down.  This would seem to support the idea that increasing ink load
> increases visual density.  It doesn't have any significance beyond
> that.  It's just the point at which there is no more uninked paper
> showing.
> 
> Regards,
> Clayton
> 
> 
> Info on black and white digital printing at    
> http://www.cjcom.net/digiprnarts.htm