Agree completely with Michael. And for folks like me who use QTR for selective toning of regular prints (not DTP or negatives), this tonal transition can be profoundly impacted. I often use "copy curve from LK" in curve development, and I can imagine this would play a measurable role. But I am just playing, not professional.
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I believe Hendrik got the desciption here
?
?
I was surprised by it, so I tried it (experiment vs theory, lol)
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Roy,
Linearization does correct everything when doing the process carefully as you say, but I suspect the resultant component curves could be very different.? Basically, at any?given density, one will lead to a different blend?of inks than the other and one will have a different ink load than the other while still accomplishing a similar linearization.
That could be important?for DTP printing, and it could also be important when focusing on the image "grittiness" that may occur when printing on high resolution potential papers (glossy or potentially baryita).? In extreme cases, I think these differences could be significant.? Maybe this falls into the "advanced concepts" category, but I can't help but want to consider and test for this in my linearization steps process.
---Michael
Your description of method 2 makes no sense.? ?
All the values are simple ratio -- darkness of one ink vs darkness of another ink.
So K vs LK and LK vs LLK -- then calculate K vs LLK.
It's just simple algebra ->>? ? (a/b)*(b/c) = (a/c)
But as you can see from Shilesh's experiment: once you linearize is fixes most anything.
On Wed, Feb? 5, 2025 at 08:41 AM, Hendrik Kuhlmann wrote:
>
> I think in his example Shilesh demonstrated the difference between the
> two approaches we are discussing.
>
> Curve 1 illustrates *method 1*: Here the printed luminosities of all
> lighter inks are referred to K (the common reference curve): To that end
> he determines the densities (for the ink setup) by those densities in
> the calibration plot at which the K-curve has the luminosities at which
> LK and LLK reach their respective minima. In his example:
>? ??? Lmin of LK was 55% step of K
>? ??? Lmin of LLK was 25% step of K
> This method 1 corresponds to using the open square for the LLK density
> in my graph.
>
> Curve 2 illustrates *method 2*: In this case one has to multiply the two
> fractions 0.55 and 0.25. This results in 0.25 * 0.55 ~ 14 for sought
> density of LLK. This method 2 corresponds to using the solid diamond for
> the LLK density in my graph.
>
> I think in the calibration guide (p.4 of calibration.pdf) both these
> methods are getting mixed. Here are the sentences which are contradictory:
>
>? ?* Method 1: "But it's necessary to have all the relative densities to
>? ? ?a common value".
>? ?* Method 2: "Mathematically this is very simple, just a multiply: LLK
>? ? ?= 38% of 32.7% of 100 ... = 12.4%"? and "... the comparison is most
>? ? ?accurate by comparing the LLK ink to the LK ink *not to the K ink*."
>
> Both method yield the same result for the required density of LLK only
> if all ink luminosities satisfy L(K) = A - b_ink*K (with A=L(K=0) the
> common luminosity of the paper and different values of b_ink by for each
> ink). This linear relation ship holds true for very small values of K.
> But for larger K all L(K) curves saturate.
>
> I hope it is clearer now.
>
> Best,
> Hendrik
>
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Your description of method 2 makes no sense.
All the values are simple ratio -- darkness of one ink vs darkness of another ink.
So K vs LK and LK vs LLK -- then calculate K vs LLK.
It's just simple algebra ->> (a/b)*(b/c) = (a/c)
But as you can see from Shilesh's experiment: once you linearize is fixes most anything.
toggle quoted message
Show quoted text
On Wed, Feb 5, 2025 at 08:41 AM, Hendrik Kuhlmann wrote:
I think in his example Shilesh demonstrated the difference between the
two approaches we are discussing.
Curve 1 illustrates *method 1*: Here the printed luminosities of all
lighter inks are referred to K (the common reference curve): To that end
he determines the densities (for the ink setup) by those densities in
the calibration plot at which the K-curve has the luminosities at which
LK and LLK reach their respective minima. In his example:
??? Lmin of LK was 55% step of K
??? Lmin of LLK was 25% step of K
This method 1 corresponds to using the open square for the LLK density
in my graph.
Curve 2 illustrates *method 2*: In this case one has to multiply the two
fractions 0.55 and 0.25. This results in 0.25 * 0.55 ~ 14 for sought
density of LLK. This method 2 corresponds to using the solid diamond for
the LLK density in my graph.
I think in the calibration guide (p.4 of calibration.pdf) both these
methods are getting mixed. Here are the sentences which are contradictory:
* Method 1: "But it's necessary to have all the relative densities to
a common value".
* Method 2: "Mathematically this is very simple, just a multiply: LLK
= 38% of 32.7% of 100 ... = 12.4%"? and "... the comparison is most
accurate by comparing the LLK ink to the LK ink *not to the K ink*."
Both method yield the same result for the required density of LLK only
if all ink luminosities satisfy L(K) = A - b_ink*K (with A=L(K=0) the
common luminosity of the paper and different values of b_ink by for each
ink). This linear relation ship holds true for very small values of K.
But for larger K all L(K) curves saturate.
I hope it is clearer now.
Best,
Hendrik
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Here is plot after linearization. Minor differences between the two curves, nothing to write home about. Likely multiple sampling and using average values would fix the minor differences.
?
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I think in his example Shilesh demonstrated the difference between
the two approaches we are discussing.
Curve 1 illustrates method 1: Here the printed luminosities
of all lighter inks are referred to K (the common reference curve):
To that end he determines the densities (for the ink setup) by those
densities in the calibration plot at which the K-curve has the
luminosities at which LK and LLK reach their respective minima. In
his example:
??? Lmin of LK was 55% step of K
??? Lmin of LLK was 25% step of K
This method 1 corresponds to using the open square for the LLK
density in my graph.
Curve 2 illustrates method 2: In this case one has to
multiply the two fractions 0.55 and 0.25. This results in 0.25 *
0.55 ~ 14 for sought density of LLK. This method 2 corresponds to
using the solid diamond for the LLK density in my graph.
I think in the calibration guide (p.4 of calibration.pdf) both
these methods are getting mixed. Here are the sentences which are
contradictory:
- Method 1: "But it's necessary to have all the relative
densities to a common value".
- Method 2: "Mathematically this is very simple, just a
multiply: LLK = 38% of 32.7% of 100 ... = 12.4%"? and "... the
comparison is most accurate by comparing the LLK ink to the LK
ink not to the K ink."
Both method yield the same result for the required density of LLK
only if all ink luminosities satisfy L(K) = A - b_ink*K (with
A=L(K=0) the common luminosity of the paper and different values
of b_ink by for each ink). This linear relation ship holds true
for very small values of K. But for larger K all L(K) curves
saturate.
I hope it is clearer now.
Best,
Hendrik
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Hello Roy,
Thank you for your comments & thoughts. Amen to experimenting.
The curve 1 and 2 renditions come from respective *.quad files data (of course pre-linearization), imported into Excel for the graphs. Indeed, density for curve 2 LLK was lower than for curve 1. LLK density in curve 1 is 25% and 14% for curve 2. I arrived at 14% density LLK for curve 2 as 0.55 (55% density of LK relative to K) multiplied by 0.25 (25% density of LLK relative to K) = ~0.14 x 100 = 14%.
For clarity:
- ·??????? Curve 1: K=100%, LK=55%, LLK=25%
- ·??????? Curve 2: K=100%, LK=55%, LLK=14%
- ·??????? Ink limits for all = 70%. No black boost.
I will linearize the 51 step readings for 2 curves later tonight, and show results. You bring up a good point that curve 2 is closer to ideal, but with more “wiggles” and it is entirely possible that linearization will throw up an error. If that happens, I will linearize using density values rather than luminosity.
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This seems worth some comments.
First -- experimenting is the best! Nothing is obvious without trying it.
So experimenting and trying things out is always recommended.
I'm not really sure where the numbers come from for the Curve 1 & 2 -- K, LK, LLK values so its hard to be sure.
(My initial feeling is the Curve 2 has the LLK too low -- like you used the .55 factor twice; but I'm not sure.)
Looking at the ink curves you can see that LLK for Curve 2 uses a lot more ink -- you said it was a lot lighter ink (.14 vs .25).
Then looking at the density curves -- what should you care about? Curve 2 is closer to "linear" than Curve 1 but these
curves are before Linearization so that's not the end result. My take would be that curve 1 is smoother and might actually be
the better one once you do the linearization. The little wiggles in curve 2 are harder to repair.
Linearize and then do the two graphs -- things will be a lot closer but the differences may tell you more.
Roy
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On Tue, Feb 4, 2025 at 08:40 PM, shileshjani wrote:
OK, so I did my experiment:
* Epson P900, OEM inks
* Only used PK, LK, and LLK on Epson Premium Luster
* Calibration printed at 70% density
* Lmin of LK was 55% step of K
* Lmin of LLK was 25% step of K
* Created curve #1, K=100%, LK=55%, LLK=25%. All limits at 70
* Created curve #2, K=100%, LK=55%, LLK=0.55 * 0.25 = ~14.
* Figure of curves below shows differences in Curves 1 and 2. But not
particularly instructive in-itself.
* Figure of printed L vs 5% steps much more decisive. The method of
referencing LLK to LK and reflecting back to K is much closer to linear than
my previous undertanding of the method.
* I kept "Gray Curve" settings at Highlight = 5, Shadow = 5, no Overlap, and
Gamma =1. The highlight and shadow values may impact results.
* I learned something.
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I can also make curve 1 behave like curve 2 by changing Highlight from 5 to 0 in the Gray Curve tab. So, I think there is no right or wrong way, rather there are a lot control variables available to achive the desired output.
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OK, so I did my experiment:
- Epson P900, OEM inks
- Only used PK, LK, and LLK on Epson Premium Luster
- Calibration printed at 70% density
- Lmin of LK was 55% step of K
- Lmin of LLK was 25% step of K
- Created curve #1, K=100%, LK=55%, LLK=25%. All limits at 70
- Created curve #2, K=100%, LK=55%, LLK=0.55 * 0.25 = ~14.
- Figure of curves below shows differences in Curves 1 and 2. But not particularly instructive in-itself.
- Figure of printed L vs 5% steps much more decisive. The method of referencing LLK to LK and reflecting back to K is?much closer to linear than my previous undertanding of the method.
- I kept "Gray Curve" settings at Highlight = 5, Shadow = 5, no Overlap, and Gamma =1. The highlight and shadow values may impact results.
- I learned something.
?
?
?
?
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Hello Paul,
?
I was only referring to K universally as the darkest ink, whether it be MK or PK. LK and LLK as the next lighter shades. In your write-up, you also refer the lighter density inks in relation to K (MK or PK) if only one K is used. This accords with my understanding of how to set ink density of successively lighter inks.
?
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On Tue, Feb 4, 2025 at 10:59?AM shileshjani via <shileshjani= [email protected]> wrote: I did not know about that guidance. That LK is a fraction of K,
Be careful?to distinguish?between MK and PK.? They are different due to the different types of coating on matte paper v. "Photo" (glossy, pearl, semigloss, & satin.? I use PK dilutions in my 9800.
... If input->output is a linear relationship, ...?
...??But we know the relationship is not linear.
They are differing, reduced slope curves.?
That said, the system is flexible enough to deal with the differences, including when the final curve is "linearized"? (and beware that the toe of the curve is the least linear part).
This is the inkset I have used for both "glossy" and matte papers (including Arches, which requires 2 MK positions to reach a good dmax):
?
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I did not know about that guidance. That LK is a fraction of K, and LLK is a fraction of LK (but reflected back in terms of K) . I have made curves from scratch and have not noticed any strange effects of LK and LLK being fraction of K. Mind you, most times I just modify existing curves. If input->output is a linear relationship, it is mathematically the same to use either method. But we know the relationship is not linear. I have to think about this. I may putz around and see what difference (visual smoothness of ramp, and amount of linearization would be needed) the 2 methods yield.
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Dear Shilesh:
Thank you very much for your reply. Very helpful, because it
clarifies the procedure. What you explain is what I was thinking
of, originally. But I was misguided by the descriptions in the QTR
User Guide and in the Calibration Guide (from the QTR website).
In the Calibration Guide it is stated on page 4: "But it's necessary to have all the relative
densities to a common value". So far so good. It is
logical and in line with what you explain. But on the same page it
is written: "Since the LLK will be
transitioning to the LK ink in the profiles the comparison is
most accurate by comparing the LLK ink to the LK ink not to
the K ink." Thereafter, a calculation is made in
which the relative density of LLK to LK is multiplied by the
relative density of LK to K, suggesting that the result of this
product would yield a more accurate relative density of LLK to K.?
- I am not convinced that the result is more accurate, because
for 3 gray inks the multiplication of fractions involves the
determination of 4 data points compared to the involvement of
only 2 data points for direct determination of the density ratio
of LLK to K. But it may depend on the method used to measure the
curves.
- More importantly, the multiplication of fractions only yields
the desired ratio of LLK to K if the functions L(K) for all inks
would be linear, i.e. if L(K) = a + b*K with some constants a
and b for all inks. But in our case the functions are
exponential of the form L(K) = a + b*exp(-c*K) with a>0,
b>0, c>0. For such functions the above multiplication of
fractions will NOT relate the gray densities to the common K
reference curve. Rather, in the example plot in my
original post for HFA-PR-308 and GCVT inks the multiplication of
fractions yields densities given by the abscissas of the
diamonds. The densities of the gray inks (all inks are gray
except for the toner) relative to the common reference ink K are
given by the abscissas of the squares (confirmed by you).
For an example, below I show part of my previous plot. C, LK and
K denote the cartridge slots. The carts are filled as follows.
C: 50%MK, LK: 100%PK, K: 100%MK. The LK cart with 100%PK prints
dark gray on matte paper. From the fits (thin curves) of the
data (circles) one obtains
- LK to K: fraction = 0.4821 (vertical red line)
- C to LK: fraction = 0.4786 (blue X)
- The product of these fractions is = 0.2307
(vertical blue dotted line)
- Compare this to the 'correct' value of the C to K density
(vertical blue line): 0.3307.
Concerning the global ink limit, you are correct. I was thinking
of using the Black Boost, because the slope of the L(K) curve for
the K channel is already very small at K=100% (with global ink
limit of 50%) and already L(K=100%) < 20 for the black ink.
You are correct regarding the toner. For the toner curve (open
blue squares on the dashed blue line in my original plot) I have
not calculated its relative density, because it requires a
separate curve in the Ink Setup to neutralize the print for all
gray values.
Thank you very much again!
Hendrik
Am 04.02.2025 um 04:35 schrieb shileshjani via groups.io:
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Hello Hendrick,
I hope this helps.
- First, I am not familar with dual K inkset described by Paul
Roark. But you mention that you printed at 50% limits on HPR
308, which is a coated MK paper, and as-such should yield Lmin
of approximately 17.7 to 16 (Dmax ~ 1.6 to 1.7) using single
MK. So you may want to look into, perhaps increase ink limit
to >50% or use "Black Boost" ~70%
- Please refer to picture below on how to set the density of
lighter shade of grey inks. Mind you this is only for 3 shades
of grey (K, LK, and LLK) as an example. Toner inks utilize the
density numbers also, but rely on "Limit" to determine how
much of the toner gets used. You that either visually, or
ideally with a spectro.
- Say at the calibration ink density, the solid blue line
represents density of K in 5% step file. Solid orange line
represnts LK ink, and solid green line is LLK ink. What you
want to do is to find Lmin of LK and LLK (dashed orange and
green lines respectively), and find the patch of K which
prints at the same density. In the case of LK (orange vertical
dash) gives you ~25%, and LLK (green vertical dash) gives you
~15%. These are the numbers you input into "Density." If I
undersand your graph, it seems you are looking at these
numbers from succesive lower density inks. That would not be
correct. All densities should be relative to K.
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Hello Hendrick,
I hope this helps.
- First, I am not familar with dual K inkset described by Paul Roark. But you mention that you printed at 50% limits on HPR 308, which is a coated MK paper, and as-such should yield Lmin of approximately 17.7 to 16 (Dmax ~ 1.6 to 1.7) using single MK. So you may want to look into, perhaps increase ink limit to >50% or use "Black Boost" ~70%
- Please refer to picture below on how to set the density of lighter shade of grey inks. Mind you this is only for 3 shades of grey (K, LK, and LLK) as an example. Toner inks utilize the density numbers also, but rely on "Limit" to determine how much of the toner gets used. You that either visually, or ideally with a spectro.
- Say at the calibration ink density, the solid blue line represents density of K in 5% step file. Solid orange line represnts LK ink, and solid green line is LLK ink. What you want to do is to find Lmin of LK and LLK (dashed orange and green lines respectively), and find the patch of K which prints at the same density. In the case of LK (orange vertical dash) gives you ~25%, and LLK (green vertical dash) gives you ~15%. These are the numbers you input into "Density." If I undersand your graph, it seems you are looking at these numbers from succesive lower density inks. That would not be correct. All densities should be relative to K.
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Dear all:
I am a beginner and I have a question regarding the determination
of the ink densities to be used under the 'Ink Setup' tab when
using multiple gray inks.?
O.k., Paul Roark calls it a 'judgement call'. With my very
limited experience I fully agree. But regardless of that I would
like to better understand the procedure which I found in several
documents. Accordingly, the ink density to be entered under 'Ink
Setup' should be the result of the product of the fractions of the
respective next darker ink which would yield the same density (or
Lab L) as the ink at 100%.
I measured the Lab L values from a print of the calibration image
for Hahnemühle Photo Rag 308, the GCVT ink set of Paul Roark,
resolution 2880-super and 50% global ink limit. The results for
each ink are shown as circles in the image below.? All data can be
well represented by exponentially decaying functions (lines).
If I follow the above mentioned standard procedure, the fractions
are indicated by the labelled plusses and the densities to be
entered under 'Ink Setup' are represented by the K values below
the full diamonds (they do not lie on the K-curve, because the ink
curves are not linear). Am I correct that these densities, i.e.
products of fractions, should be used? I am asking, because the
products of the fractions, although they certainly carry relevant
information, have no obvious meaning which would help to visually
understand the resulting ink curves.
Hendrik
PS: From the curves in my ink separation plot, is the global ink
limit I selected (50%) adequate? The lighter inks still have a
significant slope at 100%.
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Thought you would appreciate
Thought this group would appreciate this comparison. Started the classic cyanotype unit a week ago and several students’ prints came out as the one on the left so I ASSUMED the P900 profile I translated
to the P5370 would not work. I scrambled to make a new profile on the fly. ?BEFORE I saw their negatives.
?
Then I looked at the negative (and Print-Tool settings) and realized the student had not pulled down the profile so printed the negative with None (no profile) and so did the students after him, since Print-Tool
defaults to last used settings, did the same.
?
There’s always something in a gang lab. The classic cyanotype P900 on the P5370 profile works fine. And I bet those students will pay more attention next time.
?
Of course, they now have a detailed handout.
Chris
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Re: Piezography Pro Inks- UV densities
Perfect!
Thanks Richard!!
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Re: presets, settings and illusions
Thanks for this. Very informative. ?[BTW the current version DXO Photolab 8 creates four presets for the Epson 3880, but gets the names reversed for matte and photo papers.]
*
A question for those of you who are more knowledgeable than I am regarding Sequoia /Print panel/ Printer Options/ Printer Settings:
What does “Finest Detail” actually do?
I usually turn it on except for impressionist or atmospheric images, since it just sounds like a good idea for detailed images.
But, I’m don’t think I can see any difference when Output Resolution is set at 1440 or 2880. ?Seeing is, of course, what it’s all about, but still I wonder whether it actually
does?anything to what ends up on the paper at these resolutions.
Myron
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Hendrik Kuhlmann
