Digital BW, The Print

Today was my first attempt to delve a litle deeper into QTR and to try to create a 
curve.  I want to be able to do this so that at a minimum I don't have to bother Roy, 
Carl or others if I decide to try a different paper.  However, as a result I have a bunch 
of questions on which I would appreciate some help.  

To put a toe in the water I did the following:  I duplicated the EEM_2200-cool Ink 
Descriptor File provided with the download.  I changed the name to EEM_2200-test, 
deleted the LINEARIZE line at the bottom (leaving all other variables the same), created 
and installed this curve and used it to print the 21-step wedge (100% this curve).  I 
then followed the helpful directions to use Eye-One Measure Tool to measure the strip 
and calculate the densities.  I then compared these to the LINEARIZE figures in the 
EEM_2200-cool file.  I expected to get very similar numbers but did not.  Fromm 55 to 
100 I got quite different figures.  My results were:

LINEARIZE="0.029 0.079 0.142 0.215 0.294 0.374 0.463 0.547 0.635 0.717 0.802 0.
878 0.957 1.040 1.116 1.208 1.287 1.366 1.432 1.514 1.607 "

Is this sort of variance to be expected (from printer to printer) or have I done 
something wrong?

I think I almost understand the basic components of the Ink Descriptor Files but am 
not sure how many of their values have been determined.  For example looking at the 
EEM_2200-cool and warm files, why are the ink limits set at the values they are?  Is 
this just trial and error or is there some method here?  More specifically:

1) At what point does Boost kick in and why not allow it to go to 100 at the very high 
end?  (Why set it to 90 for EEM and 95 for PFA? What would it be for HPR?)
2) K is limited to the default limit which is 75.  Why?
3) Why is LK limited to 56 (cool)/ 60 (warm)?
4) I assume the limits for LC and LM need to be the same to balance against 
metamerism and that LC and LM are used to cool the Epson K and LK (and I guess it 
follows that one might lower the LK limit a little in the cool file).    Is a cool curve is 
one that takes the warm and at 50:50 is neutral?  
5) If so, how does one measure neutral?  
6) Was the cool file created by steadily increasing the limit on LC and LM until this was 
achieved?
7) Is Gray_Val of LK set to 35 because the Epson Light Black is 35% black?
8) Why is Unused_Ink_3 not set to Y?
9) When is Calibration set to Yes?  The documentation says that it is used for the two 
calibration steps but it is not mentioned again.

Also I took a peek at the sepia file and thought I would see UC_SEPIA=YES....

Sorry for the long list but I thought it would make it easier to answer.  Is there a good 
general reading source that would help me with this stuff or does one have to be a 
real technician?

Thanks in advance

Steve

On Sunday, December 21, 2003, at 06:58  PM, Steve Kale wrote:

> Today was my first attempt to delve a litle deeper into QTR and to try 
> to create a
> curve.  I want to be able to do this so that at a minimum I don't have 
> to bother Roy,
> Carl or others if I decide to try a different paper.  However, as a 
> result I have a bunch
> of questions on which I would appreciate some help.
>
> To put a toe in the water I did the following:  I duplicated the 
> EEM_2200-cool Ink
> Descriptor File provided with the download.  I changed the name to 
> EEM_2200-test,
> deleted the LINEARIZE line at the bottom (leaving all other variables 
> the same), created
> and installed this curve and used it to print the 21-step wedge (100% 
> this curve).  I
> then followed the helpful directions to use Eye-One Measure Tool to 
> measure the strip
> and calculate the densities.  I then compared these to the LINEARIZE 
> figures in the
> EEM_2200-cool file.  I expected to get very similar numbers but did 
> not.  Fromm 55 to
> 100 I got quite different figures.  My results were:
>
> LINEARIZE="0.029 0.079 0.142 0.215 0.294 0.374 0.463 0.547 0.635 0.717 
> 0.802 0.
> 878 0.957 1.040 1.116 1.208 1.287 1.366 1.432 1.514 1.607 "
>
> Is this sort of variance to be expected (from printer to printer) or 
> have I done
> something wrong?
There could be printer differences, Eye-One (or other instrument) 
differences, or differences in drying time before measurement.  This 
why it is a good idea to do your own linearization.
>
> I think I almost understand the basic components of the Ink Descriptor 
> Files but am
> not sure how many of their values have been determined.  For example 
> looking at the
> EEM_2200-cool and warm files, why are the ink limits set at the values 
> they are?  Is
> this just trial and error or is there some method here?
Some trial and error but also determined in the calibration steps 
outlined in the instructions.
>   More specifically:
>
> 1) At what point does Boost kick in and why not allow it to go to 100 
> at the very high
> end?  (Why set it to 90 for EEM and 95 for PFA? What would it be for 
> HPR?)
Roy can answer more specifically, but I think it kicks in for just the 
last few percent of the curve.  Actual value by trial and error, but 90 
or 95 is the usual value used.
> 2) K is limited to the default limit which is 75.  Why?
Measured as described in step 1 of the calibration procedure.
> 3) Why is LK limited to 56 (cool)/ 60 (warm)?
You answered this question in #4 below.
> 4) I assume the limits for LC and LM need to be the same to balance 
> against
> metamerism and that LC and LM are used to cool the Epson K and LK (and 
> I guess it
> follows that one might lower the LK limit a little in the cool file).
The idea was to adjust LC and LM, relative to LK,  to produce a very 
cool curve that could be used for blending with the warm curve to 
produce the desired tone.
>     Is a cool curve is
> one that takes the warm and at 50:50 is neutral?
It could be adjusted to do so, but perfect neutrality at 50% would be 
fortuitous.
>
> 5) If so, how does one measure neutral?
You could use the LAB or XYZ values from the Eye-One to evaluate 
neutrality.
>
> 6) Was the cool file created by steadily increasing the limit on LC 
> and LM until this was
> achieved?
I wasn't shooting for neutral with the cool curve - just a very cool 
curve that could be subsequently blended with warm to get the desired 
tone.
> 7) Is Gray_Val of LK set to 35 because the Epson Light Black is 35% 
> black?
No.  This was determined by measurement as described in step 2 of the 
calibration procedure.
> 8) Why is Unused_Ink_3 not set to Y?
Because Y is used by the UC-NEUTRALIZER function when sepia is desired 
and Y must be set to 0 otherwise.
> 9) When is Calibration set to Yes?  The documentation says that it is 
> used for the two
> calibration steps but it is not mentioned again.

I think you may have overlooked the calibration read-me file that 
describes the two step calibration procedure.
>
> Also I took a peek at the sepia file and thought I would see 
> UC_SEPIA=YES....

No longer required, this function is now included in the UC_NEUTRALIZER 
- see #8.

>
> Sorry for the long list but I thought it would make it easier to 
> answer.  Is there a good
> general reading source that would help me with this stuff or does one 
> have to be a
> real technician?
>
> Thanks in advance
>
> Steve
>

Carl

Thanks as always.  A couple of follow-on questions...


<snip...

There could be printer differences, Eye-One (or other instrument)
differences, or differences in drying time before measurement.  This
why it is a good idea to do your own linearization.>

Ok but you would agree that I am at least following the right procedure
here?


<snip...
> 2) K is limited to the default limit which is 75.  Why?
Measured as described in step 1 of the calibration procedure.>

Ok I have just now seen the Calibration.rtfd file and will work through it.
I started with Getting Started which cross refs the Ideal Density, Eye-One
and CurveInfo files but not Calibration ­ it simply says _the two
calibration steps below_ but there is no Calibration below in that file.  I
guess I will likely have a few more questions.

> 3) Why is LK limited to 56 (cool)/ 60 (warm)?
You answered this question in #4 below.

Sorry my point was why around this level in the first place (in 4 I was
simply referring to the cool curve having a slightly lower figure than the
warm).


> 4) I assume the limits for LC and LM need to be the same to balance
> against
> metamerism and that LC and LM are used to cool the Epson K and LK (and
> I guess it
> follows that one might lower the LK limit a little in the cool file).
The idea was to adjust LC and LM, relative to LK,  to produce a very
cool curve that could be used for blending with the warm curve to
produce the desired tone.
>     Is a cool curve is
> one that takes the warm and at 50:50 is neutral?
It could be adjusted to do so, but perfect neutrality at 50% would be
fortuitous.
>
> 5) If so, how does one measure neutral?
You could use the LAB or XYZ values from the Eye-One to evaluate
neutrality.
>
> 6) Was the cool file created by steadily increasing the limit on LC
> and LM until this was
> achieved?
I wasn't shooting for neutral with the cool curve - just a very cool
curve that could be subsequently blended with warm to get the desired
tone.


I guess I need a little more guidance on how you determine you have obtained
a cool curve (or neutral combination).  That is, when you are working on
_adjust[ing] LC and LM, relative to LK_ how do you know you have reached the
goal of a very cool curve (and so there is no need to go further)?


<snip...
I think you may have overlooked the calibration read-me file that
describes the two step calibration procedure.>

Yes.

One further point.  I have to say that I for one would be happy if QTR
became paid-for shareware so that Roy, Carl et al were encouraged to take
the time to improve the documentation, make additional enhancements to the
interfaces etc.  At the moment the documentation is a little all over the
place and while the how is there, there isn¹t a lot of why.  A token sum per
individual user could add up to quite an incentive and I for one would be
very happy to make a contribution.  I guess charging, however little,
creates an onus for support but I suspect most of that is being provided
already.

Thanks

Steve






[Non-text portions of this message have been removed]

I assume inkpattern.psd in the Calibration documentation is now called
inkseparation.psd?

From: Steve Kale <stevekale@...>
Reply-To: DigitalBlackandWhiteThePrint@yahoogroups.com
Date: Mon, 22 Dec 2003 18:00:09 +0000
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Subject: Re: [Digital BW] QTR and Making Curves

Carl

Thanks as always.  A couple of follow-on questions...


<snip...

There could be printer differences, Eye-One (or other instrument)
differences, or differences in drying time before measurement.  This
why it is a good idea to do your own linearization.>

Ok but you would agree that I am at least following the right procedure
here?


<snip...
> 2) K is limited to the default limit which is 75.  Why?
Measured as described in step 1 of the calibration procedure.>

Ok I have just now seen the Calibration.rtfd file and will work through it.
I started with Getting Started which cross refs the Ideal Density, Eye-One
and CurveInfo files but not Calibration ­ it simply says _the two
calibration steps below_ but there is no Calibration below in that file.  I
guess I will likely have a few more questions.

> 3) Why is LK limited to 56 (cool)/ 60 (warm)?
You answered this question in #4 below.

Sorry my point was why around this level in the first place (in 4 I was
simply referring to the cool curve having a slightly lower figure than the
warm).


> 4) I assume the limits for LC and LM need to be the same to balance
> against
> metamerism and that LC and LM are used to cool the Epson K and LK (and
> I guess it
> follows that one might lower the LK limit a little in the cool file).
The idea was to adjust LC and LM, relative to LK,  to produce a very
cool curve that could be used for blending with the warm curve to
produce the desired tone.
>     Is a cool curve is
> one that takes the warm and at 50:50 is neutral?
It could be adjusted to do so, but perfect neutrality at 50% would be
fortuitous.
>
> 5) If so, how does one measure neutral?
You could use the LAB or XYZ values from the Eye-One to evaluate
neutrality.
>
> 6) Was the cool file created by steadily increasing the limit on LC
> and LM until this was
> achieved?
I wasn't shooting for neutral with the cool curve - just a very cool
curve that could be subsequently blended with warm to get the desired
tone.


I guess I need a little more guidance on how you determine you have obtained
a cool curve (or neutral combination).  That is, when you are working on
_adjust[ing] LC and LM, relative to LK_ how do you know you have reached the
goal of a very cool curve (and so there is no need to go further)?


<snip...
I think you may have overlooked the calibration read-me file that
describes the two step calibration procedure.>

Yes.

One further point.  I have to say that I for one would be happy if QTR
became paid-for shareware so that Roy, Carl et al were encouraged to take
the time to improve the documentation, make additional enhancements to the
interfaces etc.  At the moment the documentation is a little all over the
place and while the how is there, there isn¹t a lot of why.  A token sum per
individual user could add up to quite an incentive and I for one would be
very happy to make a contribution.  I guess charging, however little,
creates an onus for support but I suspect most of that is being provided
already.

Thanks

Steve






[Non-text portions of this message have been removed]



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[Non-text portions of this message have been removed]

Steve,

On Monday, December 22, 2003, at 01:00  PM, Steve Kale wrote:
> There could be printer differences, Eye-One (or other instrument)
> differences, or differences in drying time before measurement.  This
> why it is a good idea to do your own linearization.>
>
> Ok but you would agree that I am at least following the right procedure
> here?

Yes.

>> 3) Why is LK limited to 56 (cool)/ 60 (warm)?
> You answered this question in #4 below.
>
> Sorry my point was why around this level in the first place (in 4 I was
> simply referring to the cool curve having a slightly lower figure than 
> the
> warm).

As I recall the specific values were determined some time ago using an 
earlier beta version, prior to the implementation of the linearization 
feature.  The numbers were arrived at by trial and error, with some 
guidance from Roy.  The iterative process involved setting limit values 
for LK, LC, and LM, printing and measuring step wedges, plotting the 
density curves, and finally evaluating the curves for linearity.  We 
were also trying to equalize the densities of the cool and warm curves 
and adjust them, using the ink limit values.  A mid-tone (50%) density 
of about 0.6 was also a target value for adjustment.  Roy may wish to 
clarify, but I think that the linearization makes the absolute limit 
values used less critical in this regard.

>
>> 4) I assume the limits for LC and LM need to be the same to balance
>> against
>> metamerism and that LC and LM are used to cool the Epson K and LK (and
>> I guess it
>> follows that one might lower the LK limit a little in the cool file).
> The idea was to adjust LC and LM, relative to LK,  to produce a very
> cool curve that could be used for blending with the warm curve to
> produce the desired tone.
>>     Is a cool curve is
>> one that takes the warm and at 50:50 is neutral?
> It could be adjusted to do so, but perfect neutrality at 50% would be
> fortuitous.
>>
>> 5) If so, how does one measure neutral?
> You could use the LAB or XYZ values from the Eye-One to evaluate
> neutrality.
>>
>> 6) Was the cool file created by steadily increasing the limit on LC
>> and LM until this was
>> achieved?
> I wasn't shooting for neutral with the cool curve - just a very cool
> curve that could be subsequently blended with warm to get the desired
> tone.
>
>
> I guess I need a little more guidance on how you determine you have 
> obtained
> a cool curve (or neutral combination).  That is, when you are working 
> on
> _adjust[ing] LC and LM, relative to LK_ how do you know you have 
> reached the
> goal of a very cool curve (and so there is no need to go further)?

I just did it by eye to get a curve that printed the step wedge a cool, 
blue color.  It is then much easier to use the blender in the print 
driver to get close to "neutral" or whatever other hue you prefer for 
your prints by blending the cool and warm curves.

>
> <snip...

Carl

Carl/Roy

Some observations after another evening playing around with this and hopefully a lot 
better understanding.

Using EEM and just focusing on the warm curve for now, Default Ink Limit set at 75% 
(tough on the eyes to place this one) and capping the LK at 60%, I get a much lower 
cross over point into the use of the LK ie 25 rather than 35.  (Capping LK at the 
default 75% makes little difference to this number, ie 26%.)  I also set boost at 95 
rather than 90.

Am I right in seeing the selection of this 25% point as being the point at which QTR 
switches from using LK to K to produce shades of gray, ie only LK is used from 0 to 
25 and only K is used from 26 to 100, or is it not an abrupt switchover? 

The unlinearised density values were:
   
0.039 0.087 0.153 0.224 0.305 0.375 0.464 0.548 0.632 0.705 0.783 0.862 0.949 1.
041 1.124 1.210 1.295 1.374 1.456 1.548 1.666

And the linearized density values were:

0.040 0.089 0.138 0.189 0.243 0.293 0.361 0.420 0.479 0.541 0.610 0.689 0.770 0.
855 0.938 1.031 1.148 1.242 1.361 1.496 1.623

I was surprised to see the dMax difference but both of these seem to be jumping 
around with different readings and as the ink settles.  I would expect the two 100% 
figures to be the same.

Wouldn't the lower use of LK make it easier to cool this curve rather than one with 
Gray_Ink_Val LK set to 35?

Cheers

Steve



--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Carl Schofield <scho@m...> 
wrote:

> Steve,
> 
> On Monday, December 22, 2003, at 01:00  PM, Steve Kale wrote:
> > There could be printer differences, Eye-One (or other instrument)
> > differences, or differences in drying time before measurement.  This
> > why it is a good idea to do your own linearization.>
> >
> > Ok but you would agree that I am at least following the right procedure
> > here?
> 
> Yes.
> 
> >> 3) Why is LK limited to 56 (cool)/ 60 (warm)?
> > You answered this question in #4 below.
> >
> > Sorry my point was why around this level in the first place (in 4 I was
> > simply referring to the cool curve having a slightly lower figure than 
> > the
> > warm).
> 
> As I recall the specific values were determined some time ago using an 
> earlier beta version, prior to the implementation of the linearization 
> feature.  The numbers were arrived at by trial and error, with some 
> guidance from Roy.  The iterative process involved setting limit values 
> for LK, LC, and LM, printing and measuring step wedges, plotting the 
> density curves, and finally evaluating the curves for linearity.  We 
> were also trying to equalize the densities of the cool and warm curves 
> and adjust them, using the ink limit values.  A mid-tone (50%) density 
> of about 0.6 was also a target value for adjustment.  Roy may wish to 
> clarify, but I think that the linearization makes the absolute limit 
> values used less critical in this regard.
> 
> >
> >> 4) I assume the limits for LC and LM need to be the same to balance
> >> against
> >> metamerism and that LC and LM are used to cool the Epson K and LK (and
> >> I guess it
> >> follows that one might lower the LK limit a little in the cool file).
> > The idea was to adjust LC and LM, relative to LK,  to produce a very
> > cool curve that could be used for blending with the warm curve to
> > produce the desired tone.
> >>     Is a cool curve is
> >> one that takes the warm and at 50:50 is neutral?
> > It could be adjusted to do so, but perfect neutrality at 50% would be
> > fortuitous.
> >>
> >> 5) If so, how does one measure neutral?
> > You could use the LAB or XYZ values from the Eye-One to evaluate
> > neutrality.
> >>
> >> 6) Was the cool file created by steadily increasing the limit on LC
> >> and LM until this was
> >> achieved?
> > I wasn't shooting for neutral with the cool curve - just a very cool
> > curve that could be subsequently blended with warm to get the desired
> > tone.
> >
> >
> > I guess I need a little more guidance on how you determine you have 
> > obtained
> > a cool curve (or neutral combination).  That is, when you are working 
> > on
> > _adjust[ing] LC and LM, relative to LK_ how do you know you have 
> > reached the
> > goal of a very cool curve (and so there is no need to go further)?
> 
> I just did it by eye to get a curve that printed the step wedge a cool, 
> blue color.  It is then much easier to use the blender in the print 
> driver to get close to "neutral" or whatever other hue you prefer for 
> your prints by blending the cool and warm curves.
> 
> >
> > <snip...
> 
> Carl

Steve,

On Monday, December 22, 2003, at 06:47  PM, Steve Kale wrote:

> Carl/Roy
>
> Some observations after another evening playing around with this and 
> hopefully a lot
> better understanding.
>
> Using EEM and just focusing on the warm curve for now, Default Ink 
> Limit set at 75%
> (tough on the eyes to place this one) and capping the LK at 60%, I get 
> a much lower
> cross over point into the use of the LK ie 25 rather than 35.  
> (Capping LK at the
> default 75% makes little difference to this number, ie 26%.)  I also 
> set boost at 95
> rather than 90.
Seems low for EEM with matte K, but not impossible.  Did you arrive at 
the 25% by  finding that the measured density of the 100% patch of the 
LK wedge was equal to the measured density of the 25% patch of the K 
wedge on the print of the ink separation file (printed in calibration 
mode with default ink limit set to 75 for all inks in the calibration 
profile)?
>
> Am I right in seeing the selection of this 25% point as being the 
> point at which QTR
> switches from using LK to K to produce shades of gray, ie only LK is 
> used from 0 to
> 25 and only K is used from 26 to 100, or is it not an abrupt 
> switchover?

No it is not an abrupt switch, the two inks are blended and you can see 
the transition by running the graph_curve script with your .quad warm 
curve file (from the curvedropbox).

>
>
> The unlinearised density values were:
>
> 0.039 0.087 0.153 0.224 0.305 0.375 0.464 0.548 0.632 0.705 0.783 
> 0.862 0.949 1.
> 041 1.124 1.210 1.295 1.374 1.456 1.548 1.666
>
> And the linearized density values were:
>
> 0.040 0.089 0.138 0.189 0.243 0.293 0.361 0.420 0.479 0.541 0.610 
> 0.689 0.770 0.
> 855 0.938 1.031 1.148 1.242 1.361 1.496 1.623
>
> I was surprised to see the dMax difference but both of these seem to 
> be jumping
> around with different readings and as the ink settles.  I would expect 
> the two 100%
> figures to be the same.

Mine usually are about the same dmax or higher after linearization.
>
> Wouldn't the lower use of LK make it easier to cool this curve rather 
> than one with
> Gray_Ink_Val LK set to 35?

I don't know, perhaps Roy can address this.

>
> Cheers
>
> Steve

Carl

<Seems low for EEM with matte K, but not impossible.  Did you arrive at
the 25% by  finding that the measured density of the 100% patch of the
LK wedge was equal to the measured density of the 25% patch of the K
wedge on the print of the ink separation file (printed in calibration
mode with default ink limit set to 75 for all inks in the calibration
profile)?>

LK¹s Ink Limit was set at 60.  I went through the process in the
documentation for setting the default ink limit and decided that it was a
very arbitrary call up in the 70 to 90 range.  I then decided that I would
maintain your existing ink limits for K and LK.  (Even though I note that
Roy references a higher range than a default set to 75 in his
documentation.) The documentation implies (but is not explicit) that these
limits should be determined prior to determining the partitioning.


<No it is not an abrupt switch, the two inks are blended and you can see
the transition by running the graph_curve script with your .quad warm
curve file (from the curvedropbox).>

Got it.  What is the x axis on this chart?  Ink percentage? I am surprised
to see (in the graph of the unlinearized curve file) LK peaking way up in
the 63% range and K not beginning until the high 40s, despite partitioning
at 25%.  I would love an explanation of this in layman terms.


<Mine usually are about the same dmax or higher after linearization.>

Hmmmm...I would expect the linearization curve to use a fixed dMax reading
and that the movement we see is down to reading variance/drying effects but
I guess that depends on the math.


The ink limit variables and boost variable still baffle me.  Presumably,
right up to the boost level the maximum ink deposit is 75% K coverage and
maybe the very last remnants of LK. At the boost level we kick in more ink.
Is the boost variable the level it kicks in or the ink coverage to which it
climbs?  If the latter, then why would boost not be equal to 100?
Presumably the argument is that we get good coverage at 75 (hence the
default ink density) and a push to 90/95 is plenty at the very top end.  If
this is to combat dot gain I would have thought that this would already be
factored into the underlying driver such that 100% gave maximum and optimal
coverage.  Perhaps Roy can comment on these points.

Steve





[Non-text portions of this message have been removed]

Hi Steve and Carl,

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale <stevekale@=
b...> 
wrote:
> 
> <Seems low for EEM with matte K, but not impossible.  Did you arrive at
> the 25% by  finding that the measured density of the 100% patch of the
> LK wedge was equal to the measured density of the 25% patch of the K
> wedge on the print of the ink separation file (printed in calibration
> mode with default ink limit set to 75 for all inks in the calibration
> profile)?>
> 
> LK¹s Ink Limit was set at 60.  I went through the process in the
> documentation for setting the default ink limit and decided that it was a=

> very arbitrary call up in the 70 to 90 range.  I then decided that I woul=
d
> maintain your existing ink limits for K and LK.  (Even though I note that=

> Roy references a higher range than a default set to 75 in his
> documentation.) The documentation implies (but is not explicit) that thes=
e
> limits should be determined prior to determining the partitioning.

The 2200 ink limits were done a little more adhoc rather than strictly by
my orginal documents.  The idea for cool 2200 prints is to have a
combination of LK,LC,LM play the role of one light black ink. (Basically,
instead of mixing the inks manually to get a neutral gray, the idea is
to mix them using software curves).  However the difference is that you
now have 3 inkjets delivering ink so it made sense to lower the individual
limits to make sure we don't flood the paper.

> 
> 
> <No it is not an abrupt switch, the two inks are blended and you can see
> the transition by running the graph_curve script with your .quad warm
> curve file (from the curvedropbox).>
> 
> Got it.  What is the x axis on this chart?  Ink percentage? I am surprise=
d
> to see (in the graph of the unlinearized curve file) LK peaking way up in=

> the 63% range and K not beginning until the high 40s, despite partitionin=
g
> at 25%.  I would love an explanation of this in layman terms.

I think you have the right idea about the chart -- its rotated 90deg CW
from the more natural view.  Down the page is gray values from 0K to 100K.
Across is ink percentage -- i.e. proportional to how many dots of each
ink are layed down.

Partitioning is a done by "weighting" the inks and limiting the total amoun=
t
of ink rather than by crossover points.  Secondly, because of dotgain
and the logarithmic nature of density, all the curves are pushed over
quite a bit.  I.e. where you'd think K might come in at 25% it comes in
much later like 40%.

> 
> 
> <Mine usually are about the same dmax or higher after linearization.>
> 
> Hmmmm...I would expect the linearization curve to use a fixed dMax readin=
g
> and that the movement we see is down to reading variance/drying effects b=
ut
> I guess that depends on the math.

They ought to match.  Drying/aging the inks is significant.

> 
> 
> The ink limit variables and boost variable still baffle me.  Presumably,
> right up to the boost level the maximum ink deposit is 75% K coverage and=

> maybe the very last remnants of LK. At the boost level we kick in more in=
k.
> Is the boost variable the level it kicks in or the ink coverage to which =
it
> climbs?  If the latter, then why would boost not be equal to 100?
> Presumably the argument is that we get good coverage at 75 (hence the
> default ink density) and a push to 90/95 is plenty at the very top end.  =
If
> this is to combat dot gain I would have thought that this would already b=
e
> factored into the underlying driver such that 100% gave maximum and optim=
al
> coverage.  Perhaps Roy can comment on these points.

The Boost number is another ink limit percentage.  E.G. if LIMIT_K=75 and
BOOST_K=90,  the K ink will start at a slope based on the 75 value, however=

towards the top it will "smoothly" transition into an ink limit of 90.  Thi=
s
gives an extra umph of black ink right at the end for a greater dMax.
Putting it too high though would make you reach dMax before the darkest
gray -- no separation from there on.  The underlying driver has no
builtin dotgain or optimal coverage factors -- it's totally "raw" dots.

Roy

> 
> Steve
> 
>

Roy 

Thanks for the help.  Sorry I have been away and have only just come back to
this.  Am I right in that one should determine the various ink limits (and I
am quite happy to simply take your numbers for these) and that the
partitioning should be determined with these inks limits in place?  As you
can see from this thread I am getting quite different partitioning figures
than Carl for the same ink/medium combination.  The lower partition for LK
presumably means that the ink limits for LM and LC can be lower also (?).

The partitioning process makes intuitive sense to me but the final
smoothing/curve math is way beyond me for the moment.  (Any reading material
on this that does not require a physics degree?)

Cheers

Steve

From: "Roy Harrington" <roy@...>
Reply-To: DigitalBlackandWhiteThePrint@yahoogroups.com
Date: Sun, 28 Dec 2003 05:21:27 -0000
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] QTR and Making Curves


Hi Steve and Carl,

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale <stevekale@=
b...> 
wrote:


The 2200 ink limits were done a little more adhoc rather than strictly by
my orginal documents.  The idea for cool 2200 prints is to have a
combination of LK,LC,LM play the role of one light black ink. (Basically,
instead of mixing the inks manually to get a neutral gray, the idea is
to mix them using software curves).  However the difference is that you
now have 3 inkjets delivering ink so it made sense to lower the individual
limits to make sure we don't flood the paper.

> 
> 



[Non-text portions of this message have been removed]

Hi Steve,

You're right that you ought to come up with the ink limits before deciding on
the partitioning values.  I'm not positive exactly how Carl did his curves --
it's somewhat difficult since ideally you should be partitioning the LK,LC,LM
combination rather that just the LK.   Fortunately, it's not a big problem
because the final linearization smoothes out the step wedge very well.  The
other plus is that UC_NEUTRALIZER feeds the exact same curve shape into
LK LC and LM so no matter how you change curve shapes and ink limits
the 3 inks are always used in the same proportion which avoids color
crossover problem.  So the ink limit values i.e. ratios for LK,LC,LM determine 
the color tone of the output.

The linearization or "final smoothing" is really not that complicated in
concept.  Smoothness is actually built into the partitioning and mixing of
the inks -- there are only smooth changes to all the inkjets.  The main
necessity is that it's always increasing as you go from light to dark.
Once that is true, it's a matter of a correction curve that puts the densities
in the "right place".   You can think of it as first plotting densities versus
input step values -- a bunch of (x,y) or (input,output) points.  The correction
curve is just the mirror image: x and y swapped.  If you go into Photoshop
and design a custom dot gain curve you are doing exactly the same thing.
There are some hairy looking formulas for converting between density,
luminosity and other units.  If you want more reading, Adobe has some
info buried deep in their website.   Here's a website that has some
pretty technical info, but your eyes may start to glaze over.
http://www.brucelindbloom.com/

Roy


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale <stevekale@b...> 
wrote:

> Roy 
> 
> Thanks for the help.  Sorry I have been away and have only just come back to
> this.  Am I right in that one should determine the various ink limits (and I
> am quite happy to simply take your numbers for these) and that the
> partitioning should be determined with these inks limits in place?  As you
> can see from this thread I am getting quite different partitioning figures
> than Carl for the same ink/medium combination.  The lower partition for LK
> presumably means that the ink limits for LM and LC can be lower also (?).
> 
> The partitioning process makes intuitive sense to me but the final
> smoothing/curve math is way beyond me for the moment.  (Any reading material
> on this that does not require a physics degree?)
> 
> Cheers
> 
> Steve
> 
> 
> 
> 
> From: "Roy Harrington" <roy@h...>
> Reply-To: DigitalBlackandWhiteThePrint@yahoogroups.com
> Date: Sun, 28 Dec 2003 05:21:27 -0000
> To: DigitalBlackandWhiteThePrint@yahoogroups.com
> Subject: Re: [Digital BW] QTR and Making Curves
> 
> 
> Hi Steve and Carl,
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale <stevekale@=
> b...> 
> wrote:
> 
> 
> The 2200 ink limits were done a little more adhoc rather than strictly by
> my orginal documents.  The idea for cool 2200 prints is to have a
> combination of LK,LC,LM play the role of one light black ink. (Basically,
> instead of mixing the inks manually to get a neutral gray, the idea is
> to mix them using software curves).  However the difference is that you
> now have 3 inkjets delivering ink so it made sense to lower the individual
> limits to make sure we don't flood the paper.
> 
> > 
> > 
> 
> 
> 
> [Non-text portions of this message have been removed]

Hi Roy

I am hoping to get back to ³making curves² this weekend for my 2100 (and
from there to the soft proofing profiles).  With regard to ink limits, where
do you suggest I start?  Below are the ink limits that Carl used in his cool
and warm EEM descriptor files, respectively:

N_OF_INKS=7
DEFAULT_INK_LIMIT=75

LIMIT_K=
BOOST_K=90
LIMIT_C=0
LIMIT_M=0
LIMIT_Y=0
LIMIT_LC=27
LIMIT_LM=27
LIMIT_LK=56

N_OF_INKS=7
DEFAULT_INK_LIMIT=75

LIMIT_K=
BOOST_K=90
LIMIT_C=0
LIMIT_M=0
LIMIT_Y=0
LIMIT_LC=0
LIMIT_LM=0
LIMIT_LK=60

As I noted earlier, if I adopt these ink limits I get quite different
partitioning values than those used by Carl.  Maybe this is something I am
doing wrong but I intend to start from scratch again in the morning.  I hope
to get curves done for EEM and HPR ­ adjusting for the effects of spraying
with Lyson Print Guard ­ over the weekend.

>The other plus is that UC_NEUTRALIZER feeds the exact same curve shape into
>LK LC and LM so no matter how you change curve shapes and ink limits
>the 3 inks are always used in the same proportion which avoids color
>crossover problem.

So effectively in the above cool scenario LK is limited to 27 anyway?  Sorry
I am confused by this and your next sentence:

>So the ink limit values i.e. ratios for LK,LC,LM determine
>the color tone of the output.

Do you mean they are used increasingly together but always in the proportion
of 27/110, 27/110, 56/110?  So this ink ³mix² (an equal dose of LC and LM
applied to LK ­ a virtual mix) is that which is deemed to take the LK from
warm to cold?  Ie if I could print a 100% patch of this combo it would look
cold? 

And this combo of limits is deemed to give good coverage for a 100% patch in
the same way that 75 was deemed enough for K?   I am surprised that both
27/27/56 and 0/0/60 are deemed to each give good coverage. Wouldn¹t one have
a lot more ink laid down than the other?
  
If this is the case then how is K cooled, if at all (I suspect it is not)?
I ask because, although when I look at the Ink Pattern Page printed using
calibration mode it seems that K is quite neutral, at least vs LK.  However,
I have been puzzled by the comments in the BO discussion which note (quite
clearly from the examples given) that BO prints with Epson UC K  are very
warm vs their BO Eboni counterparts.  Am I right in understanding that with
BO printing ONLY K is used (ie no LK is used) or is the warmth of BO UC due
in part to LK?  

Thanks again for your help and generosity

Steve

From: "Roy Harrington" <roy@...>
Reply-To: DigitalBlackandWhiteThePrint@yahoogroups.com
Date: Wed, 14 Jan 2004 20:08:23 -0000
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] QTR and Making Curves


Hi Steve,

You're right that you ought to come up with the ink limits before deciding
on
the partitioning values.  I'm not positive exactly how Carl did his curves
--
it's somewhat difficult since ideally you should be partitioning the
LK,LC,LM
combination rather that just the LK.   Fortunately, it's not a big problem
because the final linearization smoothes out the step wedge very well.  The
other plus is that UC_NEUTRALIZER feeds the exact same curve shape into
LK LC and LM so no matter how you change curve shapes and ink limits
the 3 inks are always used in the same proportion which avoids color
crossover problem.  So the ink limit values i.e. ratios for LK,LC,LM
determine 
the color tone of the output.

The linearization or "final smoothing" is really not that complicated in
concept.  Smoothness is actually built into the partitioning and mixing of
the inks -- there are only smooth changes to all the inkjets.  The main
necessity is that it's always increasing as you go from light to dark.
Once that is true, it's a matter of a correction curve that puts the
densities
in the "right place".   You can think of it as first plotting densities
versus
input step values -- a bunch of (x,y) or (input,output) points.  The
correction
curve is just the mirror image: x and y swapped.  If you go into Photoshop
and design a custom dot gain curve you are doing exactly the same thing.
There are some hairy looking formulas for converting between density,
luminosity and other units.  If you want more reading, Adobe has some
info buried deep in their website.   Here's a website that has some
pretty technical info, but your eyes may start to glaze over.
http://www.brucelindbloom.com/

Roy

> The 2200 ink limits were done a little more ad hoc rather than strictly by
> my original documents.  The idea for cool 2200 prints is to have a
> combination of LK,LC,LM play the role of one light black ink. (Basically,
> instead of mixing the inks manually to get a neutral gray, the idea is
> to mix them using software curves).  However the difference is that you
> now have 3 inkjets delivering ink so it made sense to lower the individual
> limits to make sure we don't flood the paper.




[Non-text portions of this message have been removed]

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale <stevekale@=
b...> 
wrote:
> Hi Roy
> 
> I am hoping to get back to ³making curves² this weekend for my 2100 (and
> from there to the soft proofing profiles).  With regard to ink limits, wh=
ere
> do you suggest I start?  Below are the ink limits that Carl used in his c=
ool
> and warm EEM descriptor files, respectively:
> 
> N_OF_INKS=7
> DEFAULT_INK_LIMIT=75
> 
> LIMIT_K=
> BOOST_K=90
> LIMIT_C=0
> LIMIT_M=0
> LIMIT_Y=0
> LIMIT_LC=27
> LIMIT_LM=27
> LIMIT_LK=56
> 
> N_OF_INKS=7
> DEFAULT_INK_LIMIT=75
> 
> LIMIT_K=
> BOOST_K=90
> LIMIT_C=0
> LIMIT_M=0
> LIMIT_Y=0
> LIMIT_LC=0
> LIMIT_LM=0
> LIMIT_LK=60
> 
> As I noted earlier, if I adopt these ink limits I get quite different
> partitioning values than those used by Carl.  Maybe this is something I a=
m
> doing wrong but I intend to start from scratch again in the morning.  I h=
ope
> to get curves done for EEM and HPR ­ adjusting for the effects of sprayin=
g
> with Lyson Print Guard ­ over the weekend.

I'm curious: Have you used Carl's curve?  Are you looking for something
particularly different?

> 
> >The other plus is that UC_NEUTRALIZER feeds the exact same curve shape i=
nto
> >LK LC and LM so no matter how you change curve shapes and ink limits
> >the 3 inks are always used in the same proportion which avoids color
> >crossover problem.
> 
> So effectively in the above cool scenario LK is limited to 27 anyway?  So=
rry
> I am confused by this and your next sentence:
Maybe its a typo, but LK=56 and LC=LM=27

> 
> >So the ink limit values i.e. ratios for LK,LC,LM determine
> >the color tone of the output.
> 
> Do you mean they are used increasingly together but always in the proport=
ion
> of 27/110, 27/110, 56/110?  So this ink ³mix² (an equal dose of LC and LM=

> applied to LK ­ a virtual mix) is that which is deemed to take the LK fro=
m
> warm to cold?  Ie if I could print a 100% patch of this combo it would lo=
ok
> cold? 

Yes, its basically like you took the 3 inks and mixed them into one bottle =
--
56 parts LK, 27 parts LC and 27 parts LM. 

> 
> And this combo of limits is deemed to give good coverage for a 100% patch=
 in
> the same way that 75 was deemed enough for K?   I am surprised that both
> 27/27/56 and 0/0/60 are deemed to each give good coverage. Wouldn¹t one h=
ave
> a lot more ink laid down than the other?

I think you're right, and if you look at the linearize densities you can se=
e that
the midtones of the cool curve are denser than the warm curve.  But the
linearization correction curve evens it all out in the end, so its not a pr=
oblem.

>   
> If this is the case then how is K cooled, if at all (I suspect it is not)=
?

There's no specific cooling of K but the LK,LC,LM inks do run out all the
way to 100% so there is some cool ink.  I think the main effect is that
once you get pretty dense the tone converges to the black ink no matter
what you do.  Plus, since you choose the blending of a warm and cool
curve at the end, you'll be choosing that based on all the ink together.

> I ask because, although when I look at the Ink Pattern Page printed using=

> calibration mode it seems that K is quite neutral, at least vs LK.  Howev=
er,
> I have been puzzled by the comments in the BO discussion which note (quit=
e
> clearly from the examples given) that BO prints with Epson UC K  are very=

> warm vs their BO Eboni counterparts.  Am I right in understanding that wi=
th
> BO printing ONLY K is used (ie no LK is used) or is the warmth of BO UC d=
ue
> in part to LK?  

I think BO printing shows the K ink color a lot more than when you have all=

the inks together.  This is especially true in the lighter areas with fewer=
 dots.

Roy

> 
> Thanks again for your help and generosity
> 
> Steve
> 
> From: "Roy Harrington" <roy@h...>
> Reply-To: DigitalBlackandWhiteThePrint@yahoogroups.com
> Date: Wed, 14 Jan 2004 20:08:23 -0000
> To: DigitalBlackandWhiteThePrint@yahoogroups.com
> Subject: Re: [Digital BW] QTR and Making Curves
> 
> 
> Hi Steve,
> 
> You're right that you ought to come up with the ink limits before decidin=
g
> on
> the partitioning values.  I'm not positive exactly how Carl did his curve=
s
> --
> it's somewhat difficult since ideally you should be partitioning the
> LK,LC,LM
> combination rather that just the LK.   Fortunately, it's not a big proble=
m
> because the final linearization smoothes out the step wedge very well.  T=
he
> other plus is that UC_NEUTRALIZER feeds the exact same curve shape into
> LK LC and LM so no matter how you change curve shapes and ink limits
> the 3 inks are always used in the same proportion which avoids color
> crossover problem.  So the ink limit values i.e. ratios for LK,LC,LM
> determine 
> the color tone of the output.
> 
> The linearization or "final smoothing" is really not that complicated in
> concept.  Smoothness is actually built into the partitioning and mixing o=
f
> the inks -- there are only smooth changes to all the inkjets.  The main
> necessity is that it's always increasing as you go from light to dark.
> Once that is true, it's a matter of a correction curve that puts the
> densities
> in the "right place".   You can think of it as first plotting densities
> versus
> input step values -- a bunch of (x,y) or (input,output) points.  The
> correction
> curve is just the mirror image: x and y swapped.  If you go into Photosho=
p
> and design a custom dot gain curve you are doing exactly the same thing.
> There are some hairy looking formulas for converting between density,
> luminosity and other units.  If you want more reading, Adobe has some
> info buried deep in their website.   Here's a website that has some
> pretty technical info, but your eyes may start to glaze over.
> http://www.brucelindbloom.com/
> 
> Roy
> 
> > The 2200 ink limits were done a little more ad hoc rather than strictly=
 by
> > my original documents.  The idea for cool 2200 prints is to have a
> > combination of LK,LC,LM play the role of one light black ink. (Basicall=
y,
> > instead of mixing the inks manually to get a neutral gray, the idea is
> > to mix them using software curves).  However the difference is that you=

> > now have 3 inkjets delivering ink so it made sense to lower the individ=
ual

> > limits to make sure we don't flood the paper.
> 
> 
> 
> 
> [Non-text portions of this message have been removed]

Roy


>I'm curious: Have you used Carl's curve?  Are you looking for something
>particularly different?

Yes I have used Carl¹s curves and I am not looking for something
exceptionally different. I am trying to get under the hood of QTR so that I
am not so dependent on others, such as Carl, to provide their curves for
various ink and paper (and spray) combinations.  For example, Carl had not
redone his HPR curves for the new release.  (If for example I switch to
using Eboni instead of UC MK, or wish to try other papers, I don¹t want to
have to bug Carl or anyone for curves.)  I thought a good place to start
would be to try to replicate Carl¹s work for, say, EEM so that I had a check
on my work.  I have been trying to understand what drives the ink limit
figures (generally and vs the documentation) and furthermore puzzled by the
differences I have found in partitioning figures even when using
similar/identical ink limits.  I am not at all suggesting Carl has not done
his work well.  I have learnt a great deal but still have further to go.


>I think BO printing shows the K ink color a lot more than when you have all
>the inks together.  This is especially true in the lighter areas with fewer
>dots.

Plus I guess the posted RC prints by Carl were made with the use of UC PK
and not MK.  I suspect PK is much warmer than MK (?)

Steve




[Non-text portions of this message have been removed]

Carl

As part of my continuing poking under the hood of QTR I printed the 21 step
wedge file 21step.psd using firstly your 100% EEM cool then 100% warm (and
then also a curve using just the 27/27/56 LC/LM/LK mix you used to produce a
cool LK in order to see clearly the hue of the cooled LK).  In each printout
there is on the top 1/3 part of the strip which has the smoothed transition
a dark patch from 100 to say 97, ie at smooth transition abruptly stops
around 97 and 97-100 is the same shade of grey.  I suspect that this should
not be the case ­ it is not that way on the screen.  What¹s causing this?
Is it simply that the two ends of this image are not part of the scale? ­ I
note that when looking at the stepped (bottom) part of each image the 100
and 0 blocks are wider than the rest and the dark patch I see kicks in
exactly 1cm to the left of the right side 100% marker (each 5% block being
1cm).  If this is the case I am surprised that the extra bit on the left is
abruptly darker than where the 100% mark would be.

Can you also explain to me the second scale on this file ie 0-160.

Cheers

Steve






[Non-text portions of this message have been removed]

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale <stevekale@=
b...> 
wrote:
> Carl
> 
> As part of my continuing poking under the hood of QTR I printed the 21 st=
ep
> wedge file 21step.psd using firstly your 100% EEM cool then 100% warm (an=
d
> then also a curve using just the 27/27/56 LC/LM/LK mix you used to produc=
e a
> cool LK in order to see clearly the hue of the cooled LK).  In each print=
out
> there is on the top 1/3 part of the strip which has the smoothed transiti=
on
> a dark patch from 100 to say 97, ie at smooth transition abruptly stops
> around 97 and 97-100 is the same shade of grey.  I suspect that this shou=
ld
> not be the case ­ it is not that way on the screen.  What¹s causing this?=

> Is it simply that the two ends of this image are not part of the scale? ­=
 I
> note that when looking at the stepped (bottom) part of each image the 100=

> and 0 blocks are wider than the rest and the dark patch I see kicks in
> exactly 1cm to the left of the right side 100% marker (each 5% block bein=
g
> 1cm).  If this is the case I am surprised that the extra bit on the left =
is
> abruptly darker than where the 100% mark would be.
> 
> Can you also explain to me the second scale on this file ie 0-160.
> 
> Cheers
> 
> Steve
> 

Hi Steve,

I haven't seen the gradient so maybe Carl can comment on that.
In general though the 95-100 range has very steep curves in the black ink
so it is a hard area to deal with.

As far as the 21step image, the reason the 0 and 100 patches are slightly
wider is because Photoshop does gradients that way.  Do a gradient and
posterize, and that's what you get.  I always thought it strange, too.

The scale at the bottom of 0-160 is a little outdated, but it was target
densities when I was individually measuring patches and my dMax was 160.

Cheers,
Roy

BTW, I think it great for you to get up to speed understanding and making
profiles.  The more the merrier.  I find looking at the ink graphs to be th=
e
best way to understand what various changes do.

Roy

Steve,

I'm not sure I follow what you did, but If you made a curve with just 
LC/LM/LK and then printed a step wedge with this profile it might look 
strange because you have no K.  I haven't used the 21 step.psd file 
with the wedge you mentioned so I don't know how it prints with these 
profiles.  I just wonder if the bands you are getting are from 
posterization.

Carl

On Saturday, January 24, 2004, at 02:05  PM, Steve Kale wrote:

> Carl
>
> As part of my continuing poking under the hood of QTR I printed the 21 
> step
> wedge file 21step.psd using firstly your 100% EEM cool then 100% warm 
> (and
> then also a curve using just the 27/27/56 LC/LM/LK mix you used to 
> produce a
> cool LK in order to see clearly the hue of the cooled LK).  In each 
> printout
> there is on the top 1/3 part of the strip which has the smoothed 
> transition
> a dark patch from 100 to say 97, ie at smooth transition abruptly stops
> around 97 and 97-100 is the same shade of grey.  I suspect that this 
> should
> not be the case – it is not that way on the screen.  What’s causing 
> this?
> Is it simply that the two ends of this image are not part of the 
> scale? – I
> note that when looking at the stepped (bottom) part of each image the 
> 100
> and 0 blocks are wider than the rest and the dark patch I see kicks in
> exactly 1cm to the left of the right side 100% marker (each 5% block 
> being
> 1cm).  If this is the case I am surprised that the extra bit on the 
> left is
> abruptly darker than where the 100% mark would be.
>
> Can you also explain to me the second scale on this file ie 0-160.
>
> Cheers
>
> Steve
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
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Carl

OK ignore the fact that I also printed it with an LK/LC/LM curve (although this was 
done simply by only using the 3 inks - limit K=0 - with UC-Neutraliser which creates 
a virtual ink mix in the proportions set under the ink limits 27/27/56 - set the 
number of gray parts  to 1 and LK = 100 in the and you can see how the "cooled LK 
mix" looks across a step wedge - I didn't bother linearising etc because I just wanted 
to see the hue of LC/LM/LK mixed in those proportions).  I simply printed the file 
using the cool curve and then again with the warm curve - I was simply wanting to 
have a reference page as to how each curve printed the step wedge.  The change is 
very abrupt with a clear straight right edge and then consistent tone from there to the 
left edge.  To the right of where this effect occurs is an even tonal change down to 
white but beginning a good notch lower (ie no other bands). This is why I thought the 
left most 4mm (the amount by which the 100% block exceeds the size of every other 
block except the 0%) was not on the scale.  But then I would expect the printout to 
gradually darken from right to left so that the dmax was reached 4mm in - just as it 
appears on the screen.  But there is a clearly visible increase in density on both 
printouts.  The middle and bottom parts of the step wedge (where the image is 
stepped) show consistent tone from the right side of the 100% step to the edge of the 
page).  If you print the file you should very easily see the effect I am seeing - or 
perhaps not at all in which case I have something screwy going on.

Cheers

Steve


 --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Carl Schofield <scho@m...> 
wrote:

> Steve,
> 
> I'm not sure I follow what you did, but If you made a curve with just 
> LC/LM/LK and then printed a step wedge with this profile it might look 
> strange because you have no K.  I haven't used the 21 step.psd file 
> with the wedge you mentioned so I don't know how it prints with these 
> profiles.  I just wonder if the bands you are getting are from 
> posterization.
> 
> Carl