QTR-Quadtone RIP

I have been happily using QTR with included profiles for a couple of
years and finally acquired a Datacolor PrintFIX PRO to try my hand at
new profiles.  My printer is an Epson 4000 with stock UC ("K2") inks -
not  optimal, I realize, but surely capable of something a bit
smoother than Black-Only printing when grain is not the goal.

I have a couple of boxes of Crane Museo Silver Rag on hand - glossy,
with a slight surface stipple.  It came out about the same time as
Innova F-Type Gloss and Hahnemuhle Fine Art Pearl.  My objective is
partly to achieve something crisper and with better dMax than the
matte papers... but mostly just to learn at this early stage.

Initial ink separation revealed a nearly linear LK curve.  PK was
linear to 30 and then very slowly folded over and remained nearly flat
after 70.  It even dropped 0.02 - 0.03 from 95 to 100.  Unlimited
PK100 was 2.17.

However, Tom Moore's User Guide suggests looking "for a patch where it
appears that all the paper is covered with ink".  By eye, I can
distinguish transitions up to 50 - but not after that.  So, I chose 50
for Default Ink Limit.

Is that in fact the best strategy?  Choose the patch after which no
further transitions are visible?

Reprinting the ink separation page, limited to 50 this time, I could
see PK transitions up to 75 - but no further.  I was tempted to go
back and try a lower Default Ink Limit, but I pressed ahead.

Measurements showed LK100 to be 1.13, which is between PK40 and PK45 -
41.79, to be precise.  PK100 had dropped from 2.17 to 2.06.

So, for my initial Warm curve, I set Black Boost to 0, LK Density to
42, and left LK Limit clear.  This produced a smooth ramp, but dMax
was only 2.10.  Next, I bumped Black Boost all the way to 100, which
produced another smooth ramp with dMax at 2.25.  I linearized,
measured again, and compared with the "ideal density" curve for
dMax=2.25.  Other than the fact that Crane MSR white is 0.06, the
linearized and ideal curves are virtually identical.  I assume this
means success, right?  Keith Cooper's Northlight Images B&W test print
looked very nice (although obviously warm).  The circular gradient
showed a couple of bands, but that's a difficult hurdle to cross in my
experience.

Now for a cool curve, which will bring me to my question about LK ink
limit.  I left Black Boost at 100, LK Density at 42, and set LC/LM
Limits at 25.  I left LK Limit clear.  Yes, clear.  Why?  Because I
wanted to see what kind of failures lead most other profiles to
limiting LK.  Tom Moore makes a fairly strong point about that.  The
resulting ramp was smooth... but too cold for my taste, and even a
minor tint of rosiness.

I dropped LC/LM limits down to 12 and left everything else alone
(including LK Limit clear).  The result looked good to my eyes, so I
linearized (dMax 2.26) and compared with the ideal 2.25 curve.  Again,
virtually a perfect match.

So... should I have limited LK somewhere in the 50-60 range?  What
would have changed?  As soon as I get another couple of hours, I'll
probably try that.  Meanwhile, should I acquire a loupe and be looking
for something specific in the way of "ink flooding"?

This is all very subjective, and I'm relying upon you experts to steer
me as I begin this voyage.  Thanks in advance for your patience in
wading through this report!

Michael Miller (MiloGiacomoRambaldi47@yahoo.com)
Atlanta, GA

milogiacomorambaldi47 wrote:
> ...
> So... should I have limited LK somewhere in the 50-60 range?  What
> would have changed?  As soon as I get another couple of hours, I'll
> probably try that.  Meanwhile, should I acquire a loupe and be looking
> for something specific in the way of "ink flooding"?
> 
If you don't set an individual limit for LK it will revert to the 
Default setting of 50 - you have therefore set a limit for it.

The rest of your method sounds okay with the possible exception of the 
black boost of 100. That will probably be overinking but will be 
restricted to the very deepest blacks.

Howard

--
www.howardshaw.org

> The rest of your method sounds okay with the possible exception of
the black boost of 100. That will probably be overinking but will be
restricted to the very deepest blacks.
> 
> Howard

Howard,

Thank you for your comment about overinking.  Looking more closely at
QTR distributed profiles for Epson 4000, I see a "rule of thumb" that
WARM profiles have Black Boost +10 above Default Ink limit... and that
COOL profiles boost only +5... presumably because cools mix in some
LC/LM and try to avoid overinking by reducing Black Boost.

Following that rule of thumb, I constructed/measured/printed
additional Crane Museo Silver Rag curves:

Curve BlackBoost LClimit LMlimit dMax
Warm1          0       0       0 2.10
Warm2        100       0       0 2.25
Warm3         60       0       0 2.13
Cool2        100      12      12 2.26
Cool4         55      18      18 2.11

The numbers suggest that Black Boost swamps LC/LM Limit for dMax.  The
21-step plots - IN TERMS OF 95/100 PERCEPTUAL TRANSITION - suggest
that Warm2 and Warm3 are identical... and that Cool2 and Cool4 are
identical.  The circular gradients of Keith Cooper's B&W test image
suggest that  Warm2 beats Warm3... and that Cool2 beats Cool 4 (i.e.,
Black Boost 100 creates a smoother gradient than +10/+5 over Default
Ink Limit).

Are these observations due to aberrant Epson 4000 behavior on glossy
papers?  DO Epson 4000 UC/K2 inks behave quite differently on matte
papers?

As a retired scientist/engineer, I'd really welcome some solid theory
and supporting evidence for what to measure and observe.  Any ideas? 
As always, thanks in advance for your patience and considered opinions.

Michael Miller
MiloGiacomoRambaldi@...
Atlanta, GA

I'm still looking for heuristics for selecting the best Default Ink
Limit.  This seems to be an important first step, but the best
approach seems unclear.

To recap the discussion so far, I chose 50 for Crane Museo Silver Rag
(glossy paper) because the transition from 45 to 50 was the highest
that I could visually distinguish (even though PFP measured steadily
rising values to 100).

Quoting my original posting:

"Reprinting the ink separation page, limited to 50 this time, I could
see PK transitions up to 75 - but no further. I was tempted to go
back and try a lower Default Ink Limit, but I pressed ahead."

In the end, 50 turned out to be a reasonable choice.  Regardless of
whether I set Black Boost to 55, 60, or 100... the linearized curves
always produced good shadow detail.

So far, so good.

Then I tried the process again, this time with Moab Kayenta Photo
Matte (matte paper with OBAs, now discontinued, although still
available in large quantities, no curves in standard QTR distribution,
suggested by Moab for proofing Moab Entrada Bright - which does have
curves in standard QTR distribution).

Out of curiosity, I checked the Entrada Bright curves for the Epson
4000.  If Kayenta is for proofing Entrada Bright, then I'd expect
similar ink limits, right?  FYI, the ink limit for Entrada Bright is
50 in the QTR distribution.

So... when I printed the first Kayenta ink separation - unlimited -
and let it dry overnight, I could easily distinguish transitions to
40, barely to 50.  On the surface, that appeared to be in line with
Entrada.  However, I was a bit nervous and chose 45 instead of 50.

When I printed the second Kayenta separation - limited to 45 - and let
it dry overnight, I could easily distinguish transitions to 65, barely
to 80, certainly no further.

Recalling that I could see photo black transitions in ink-limited
Museo Rag up to 75 and still get good shadow details from the curves,
I pressed ahead.

Bad idea.  The 95/100 transitions for preliminary curves were only
barely distinguishable... not at all acceptable for shadow detail.

What to do?  Recall that ink limit 45 resulted in easily
distinguishable transitions to 65, barely to 80.  I set the goal of
finding an initial ink limit that would produce barely distinguishable
transitions to 100.  I tried 40, 35, and finally 30... which was
easily distinguishable to 90 and barely to 100.

Good idea.  The 95/100 transitions for preliminary curves were easily
distinguishable... excellent for shadow detail.

What about dMax?  Here are some interesting numbers:

1.62 - MK unlimited
1.57 - MK limited to 45
1.41 - MK limited to 30
1.60 - MK + LK limited to 45 (Warm, Black Boost=55)
1.54 - MK + LK limited to 30 (Warm, Black Boost=40)
1.57 - MK + LK limited to 45 (Cool, Black Boost=50)
1.49 - MK + LK limited to 30 (Cool, Black Boost=35)

Bottom line:  holding shadow detail in Kayenta gives up 0.08-0.13 dMax
compared to MK unlimited,  whereas Crane Silver Rag only gives up
0.04-0.06 - half as much.

Two questions:

1.  Do matte papers typically exhibit this behavior compared to
glossy?  I've only done one of each, so I really don't know.

2.  What about the Gray Curve tab?  So far, I've always left Highlight
= Shadow = 6.  Is it worth increasing Black Boost (even to 100) to
regain dMax and then increasing Shadow (10? 20?) to lighten the bottom
transitions?

--- In QuadtoneRIP@yahoogroups.com, "milogiacomorambaldi47"
<milogiacomorambaldi47@...> wrote:
>
> I'm still looking for heuristics for selecting the best Default Ink
> Limit.  This seems to be an important first step, but the best
> approach seems unclear.

I'd like to ask a related question.  I'm creating curves for a 2100
with Cone K7 inks.  Most of the curves that Cone supplies are
"pre-compiled".  That is, there are .quad files but no .qidf files. 
Roy supplies a .qidf for HPR for several printers.  I'm using this as
the starting point for my curves.  In this curve definition, the
default limit is set, but all the other limits are blank.  Is this
standard practice for K7 curves?  What does leaving this blank do? 
Why not specify a limit for each grey based on where the differences
cease to be visible?

Ferdinand

--- In QuadtoneRIP@yahoogroups.com, "milogiacomorambaldi47"
<milogiacomorambaldi47@...> wrote:
>
> I'm still looking for heuristics for selecting the best Default Ink
> Limit.  This seems to be an important first step, but the best
> approach seems unclear.
> 

Milo (?), I don't know about heuristics but this is what I do.
When the transitions on the initial 100% calibration print cease to be
at least 0.03 density ( or approx 0.075 Lab L*), I select that or the
previous step as the default limit and reprint the calibration chart
with it. For me, doing it that way has always prevented the error
problems in linearizing the curve later on. If you have the
measurement tool, I would use it's #s rather than visual estimates.

> 
> "Reprinting the ink separation page, limited to 50 this time, I could
> see PK transitions up to 75 - but no further. 

You can leave all inks at the default limit ie: don't put any value
into the separate limit boxes for each ink, but you don't have to. You
can use different limits for each ink. Whatever you put in those boxes
will over ride the default, is my understanding. I don't know if
limiting the lighter inks a lot more than the default will impact
smoothness of results or not but I think it is likely that it would.

What I am wondering is why you aren't seeing transitions farther up
the scale with the PK. Where was it on the initial 100% limit
calibration print? I would be tempted to limit it a bit more than the
default for K until it transitions better or just lower the default
limit a bit more.
> 
  Regardless of
> whether I set Black Boost to 55, 60, or 100...
> 

Roy has stated several times that you should not use more than 110 to
 115% of default limit for your boost value. As you have noted it only
is supposed to impact maximum K ink.

>
> Two questions:
> 
> 1.  Do matte papers typically exhibit this behavior compared to
> glossy?  I've only done one of each, so I really don't know.
> 
> 2.  What about the Gray Curve tab?  So far, I've always left Highlight
> = Shadow = 6.  Is it worth increasing Black Boost (even to 100) to
> regain dMax and then increasing Shadow (10? 20?) to lighten the bottom
> transitions?
>

Papers can and do vary quite significantly for both types.

I would first get a good feel for what is needed with regard to
limits,boost and the relative densities of the K & LK inks before
adding more variables to the equation. See that overlap is 0 to keep
d'max as high as possible also. After you have a nicely transitioned
21 step scale and can linearize it without trouble, is the time to go
back and play with the different variables to see what they actually
do IMHO.

Regards,
Duane

Duane,

Now we're talking heuristics:

1.  Default Ink Limit when density increase < 0.03.

2.  Black Boost no more than 1.15 x Default Ink Limit.

As it happened, my values for Moab Kayenta Matte were very close to
those suggestions.  So, in the spirit of exploring other variables, I
tried systematic variations for both warm and cool curves with most
combinations of:

1.  Shadow = 6, 12, 18, 24, 300 (maximum allowable).
2.  LK Limit = Default (045), 036.

Best dMax AND shadow detail, for both warm and cool, popped out for:

1.  Shadow = 300.
2.  LK Limit = 036.

So, the next round will hold Shadow = 300 and vary LK Limit (040, 030,
025, 020).  Will report back soon.

   


--- In QuadtoneRIP@yahoogroups.com, "dlruckus" <dlruckus@...> wrote:

>
> --- In QuadtoneRIP@yahoogroups.com, "milogiacomorambaldi47"
> <milogiacomorambaldi47@> wrote:
> >
> > I'm still looking for heuristics for selecting the best Default Ink
> > Limit.  This seems to be an important first step, but the best
> > approach seems unclear.
> > 
> 
> Milo (?), I don't know about heuristics but this is what I do.
> When the transitions on the initial 100% calibration print cease to be
> at least 0.03 density ( or approx 0.075 Lab L*), I select that or the
> previous step as the default limit and reprint the calibration chart
> with it. For me, doing it that way has always prevented the error
> problems in linearizing the curve later on. If you have the
> measurement tool, I would use it's #s rather than visual estimates.
> 
> > 
> > "Reprinting the ink separation page, limited to 50 this time, I could
> > see PK transitions up to 75 - but no further. 
> 
> You can leave all inks at the default limit ie: don't put any value
> into the separate limit boxes for each ink, but you don't have to. You
> can use different limits for each ink. Whatever you put in those boxes
> will over ride the default, is my understanding. I don't know if
> limiting the lighter inks a lot more than the default will impact
> smoothness of results or not but I think it is likely that it would.
> 
> What I am wondering is why you aren't seeing transitions farther up
> the scale with the PK. Where was it on the initial 100% limit
> calibration print? I would be tempted to limit it a bit more than the
> default for K until it transitions better or just lower the default
> limit a bit more.
> > 
>   Regardless of
> > whether I set Black Boost to 55, 60, or 100...
> > 
> 
> Roy has stated several times that you should not use more than 110 to
>  115% of default limit for your boost value. As you have noted it only
> is supposed to impact maximum K ink.
> 
> >
> > Two questions:
> > 
> > 1.  Do matte papers typically exhibit this behavior compared to
> > glossy?  I've only done one of each, so I really don't know.
> > 
> > 2.  What about the Gray Curve tab?  So far, I've always left Highlight
> > = Shadow = 6.  Is it worth increasing Black Boost (even to 100) to
> > regain dMax and then increasing Shadow (10? 20?) to lighten the bottom
> > transitions?
> >
> 
> Papers can and do vary quite significantly for both types.
> 
> I would first get a good feel for what is needed with regard to
> limits,boost and the relative densities of the K & LK inks before
> adding more variables to the equation. See that overlap is 0 to keep
> d'max as high as possible also. After you have a nicely transitioned
> 21 step scale and can linearize it without trouble, is the time to go
> back and play with the different variables to see what they actually
> do IMHO.
> 
> Regards,
> Duane
>

This message concludes my quest for profiles for Moab Kayenta for
Epson 4000 with UC inks.  Along the way, I've built 24 curves (12 each
for warm and cool - none for sepia and selenium, sorry) and linearized
six.  The final two QIDF files are now in:

	Files > Curves > Epson 4000 > MiloUC.zip > MoKPM205

along with:

	MoKPM205_Densities.xls
	MoKPM205_Versions.xls

spreadsheets documenting the exploration.  A pair for Crane Museo
Silver Rag is also included in MiloUC.zip > CrMSR.  If anybody else is
out there using this antiquated printer and inks, perhaps these files
may be useful.

The fundamental problem was achieving decent dMax without muddy
shadows.  Some suggestions from forum members proved useful, so – in
the spirit of sharing for the common good – herewith is a summary of
what I tried and learned.

First, a note about notation.  Labels such as "Ink030-Cool-V1Linear"
and "Ink045-Warm-v12" refer to version tags and worksheet labels in
the spreadsheets.  Since only the truly motivated will download and
unzip these files, here are a few notes to guide the exposition:

[Ink100] – Unlimited ink separation.  By eye, I chose 045 for Default
Ink Limit, which exactly matched Duane's subsequent suggestion to stop
when density increment falls below 0.03.

[Ink045], [Ink045-{Warm,Cool}-v1] – Limited ink separation for 045 and
first two curves.  Respectable dMax (1.60 warm, 1.57 cool), but muddy
shadows.  So, as reported earlier, I set the goal of finding a Default
Ink Limit that would produce distinguishable transitions to 100 in the
ink separation. I tried 40, 35, and finally 30... which was easily
distinguishable to 90 and barely to 100.

[Ink030], [Ink030-{Warm,Cool}-v1{Linear}] – Limited ink separation for
030 and first two curves plus linearizations.  Great shadow detail,
but disappointing dMax (1.54 warm, 1.49 cool).  What to do?  Duane had
cautioned against pushing Black Boost any further and had mentioned
limiting Light Black instead.  I didn't pick up on that at first. 
Instead, I decided to go back to 045 and explore increasing Shadow
(ultimately a dead end, as we will see).

[Ink045-{Warm,Cool}-v[2-5]] – Versions for Shadow = 12, 18, 24, 300
(maximum allowed), all with Default Ink Limit (045) for Light Black. 
Still too muddy in the shadows.  Finally decided to tinker with LK Limit.

[Ink045-{Warm,Cool}-v[6-11]] – Versions with Shadow = 300 (mostly) and
LK Limit = 40, 36, 30, 25, 20.  V11 (Shadow = 300, LK Limit = 20) was
nice.  Good shadow detail and impressive (for this matte paper) dMax
(1.64 warm, 1.62 cool).

[Ink045-{Warm,Cool}-v11Linear] – Now linearized and compared with
ideal.  Not bad.  Tempted to push LK Limit below 20, but that seemed
extreme.  Should I have gone lower?  Tempted to stop and declare
victory, but wondered if Shadow = 300 was really necessary.

[Ink045-{Warm,Cool}-v12] – LK Limit still at 20, but Shadow back to 6.
 Graphed against earlier v11 with Shadow at 300.  Unlinearized curves
clearly show some Shadow contribution to lightening – but more in
midtones than shadows, where I had expected it.

[Ink045-{Warm,Cool}-v11..12Linear] – Both v11 and v12 linearized and
compared with ideal.  Surprise!  Essentially no difference between
Shadow = 6 and Shadow = 300.  By Occam's Razor, v12 wins (the version
uploaded to Files).

Conclusions:

1.  Choose Default Ink Limit when density increment falls below 0.03.

2.  Black Boost no more than 1.15 * Default Ink Limit (actually 1.22
for my Warm version because I was using the old heuristic of +5 for
cool boost and +10 for warm boost).

3.  Leave Shadow alone.  By implication, leave Highlight alone?

4.  Try alternative LK Limits to maximize dMax and unblock shadows. 
With more gray inks than Black and Light Black, this would require
some actual understanding of what is going on when ink meets paper. 
Otherwise, the number of combinations would get out of hand quickly. 
How do you folks deal with that?

5.  In the end, the only important goal would seem to be to maximize
dMax and to mimic the ideal density curve for that value.  Are there
any other ancillary goals?

Additional comments and observations would be much appreciated...
because the next quest is to streamline this process and apply it to
the new kids on the block:

	Hahnemuhle Fine Art Baryta
	Harman Fiber-Base Alumina
	Ilford Galerie Gold Fiber Silk

No doubt their glossy natures will impact ink limits significantly. 
Any tips about that?  I also dread problems with bronzing and gloss
differential, but perhaps PremierArt PrintShield will help.  More
later as insights develop.  Thanks again for your patience and helpful
comments.