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Boost K

Boost K

2016-08-10 by stefanchristiansen@...

Hi all,



I have questions regarding the "BOOST K" option.

A forum search tells me about the last 10%, or "the end of the slope", but I'd like to know more precisely how it affects the K curve.

- Would the difference between the LIMIT K and the BOOST K values affect where in the curve the boost effect will start, or is it locked to a particular point? Then which point?

I sometimes use curves where the output is set at 100% from the 80% input or so (for 2d layer negatives, cf. screen capture). It seems I mesure on my negatives higher values in the 100% patch than in the 95% patch, though both have the same 100% output values. I never use the BOOST K option and leave it blank.

- Is there a hidden default BOOST K fonction that only apply to the 100% input value, or to the very last values?
- How would the BOOST K apply to my 2d layer negative curve: would it boost all the 100% output values or only those "at the end of the slope"?
- Is it OK to leave the BOOST K blank, or should I make it the same as the K ink limit to get no effect?
- Is there a way to boost the output for the 100% K input values only?
- Does the BOOST K fonction work the same way for all printers (I use a 1430 and a 3880)?

Thanks for your help,


Stefan Christiansen



Re: Boost K

2016-08-10 by stefanchristiansen@...

Screen capture added in "Stefan Christiansen" album in case it doesn't show in the message...

Re: Boost K

2016-08-10 by richard@...

I couln't figure out how to embed an image in the post so I put it in the photos section, but that wasn't showing up either... So I just put it into a blog post that explains this in a little more detail.

Basically, the boost is being applied to the entire scale based on what I now assume is a predefined curve built into the .quad generation program.

Here is a screenshot from the post that should illustrate this: The curve I made used a gamma setting applied to each of the 256 steps times the difference between the boost and the ink limit. The QTR generated one is slightly different which is why I think it is using a predefined curve and not some gamma setting.



To answer some of your more specific questions:

Is there a hidden default BOOST K fonction that only apply to the 100% input value, or to the very last values?

- Not unless it is assigned in the K_boost setting_

- How would the BOOST K apply to my 2d layer negative curve: would it boost all the 100% output values or only those "at the end of the slope"?

- I am not sure I fully understand the question, but the boost is dependent on whatever you Gray_Ink_1= is if you had that set to the yellow ink, the K boost would boost that ink only.

- Is it OK to leave the BOOST K blank, or should I make it the same as the K ink limit to get no effect?

- Leaving it blank will not result in some hidden default k boost setting so if you do not want to use it you can just leave it black.

- Is there a way to boost the output for the 100% K input values only?

- Yes, but you need to open the quad curve in a text editor, change the last value for each of the inks to whatever you want it to be and then save it with a different name and then reinstall the quad curves.

- Does the BOOST K fonction work the same way for all printers (I use a 1430 and a 3880)? Yes, it seems to be consistent for all the printers.

Here is a link to the full post with some of the funny math I did to get there...


Hope that helps,
Richard Boutwell

http://www.richardboutwell.com/


Re: [QuadtoneRIP] Re: Boost K

2016-08-10 by Roy Harrington

Thanks, Richard. Nice demo and graphing of the boost effect.

Also very good demonstration of testing and figuring out what a feature does.

---

For the math inclined it's simply a gamma-like function chosen so that the
left end slope matches the slope of LIMIT_K line and the right end-point matches
the BOOST_K value. It affects the whole range but mostly on the right end.
(formulas are good but seeing it is much more informative :)

Roy
Show quoted textHide quoted text
On Wed, Aug 10, 2016 at 10:05 AM, richard@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:


I couln't figure out how to embed an image in the post so I put it in the photos section, but that wasn't showing up either... So I just put it into a blog post that explains this in a little more detail.

Basically, the boost is being applied to the entire scale based on what I now assume is a predefined curve built into the .quad generation program.

Here is a screenshot from the post that should illustrate this: The curve I made used a gamma setting applied to each of the 256 steps times the difference between the boost and the ink limit. The QTR generated one is slightly different which is why I think it is using a predefined curve and not some gamma setting.



To answer some of your more specific questions:

Is there a hidden default BOOST K fonction that only apply to the 100% input value, or to the very last values?

- Not unless it is assigned in the K_boost setting_

- How would the BOOST K apply to my 2d layer negative curve: would it boost all the 100% output values or only those "at the end of the slope"?

- I am not sure I fully understand the question, but the boost is dependent on whatever you Gray_Ink_1= is if you had that set to the yellow ink, the K boost would boost that ink only.

- Is it OK to leave the BOOST K blank, or should I make it the same as the K ink limit to get no effect?

- Leaving it blank will not result in some hidden default k boost setting so if you do not want to use it you can just leave it black.

- Is there a way to boost the output for the 100% K input values only?

- Yes, but you need to open the quad curve in a text editor, change the last value for each of the inks to whatever you want it to be and then save it with a different name and then reinstall the quad curves.

- Does the BOOST K fonction work the same way for all printers (I use a 1430 and a 3880)? Yes, it seems to be consistent for all the printers.

Here is a link to the full post with some of the funny math I did to get there...









--
Roy Harrington
roy@harrington.com
www.harrington.com

Re: [QuadtoneRIP] Re: Boost K

2016-08-10 by Stefan Christiansen

More to learn and understand that I thought…

My profiles are very basic, all channels following one curve, no gray partition.
I tested two profiles, with and without a BOOST K value (LIMIT_K=20 ; BOOST_K=30).
There is no difference showing in the quad curves observed either with "QTR Curve" or with a text editor.

From Richard's answer, my guess is that for the BOOST K to be active, the profile must have a gray partition. Is this correct?

Editing and reinstalling a quad curve is a finer option I will try.

Thank you.


Stefan Christiansen

Re: [QuadtoneRIP] Re: Boost K

2016-08-11 by Stefan Christiansen

Richard,

If something isn't right, it might be due to the over-simplification of my profiles. To much info delated?
They work anyway, except for the boost feature that I want to be sure is not taking place without my permission…
The curve here is just for testing how the flat 100% output portion would be affected. I guess a boost that works would not keep it flat?

The .quad texts are awfully long, and it's easier to compare them (K curve values) in side by side windows. Hope the files will be attached in the post.

Stefan Christiansen


Test3.txt file:

N_OF_INKS=8
DEFAULT_INK_LIMIT=

LIMIT_K=20
BOOST_K=
LIMIT_C=20
LIMIT_M=20
LIMIT_Y=20
LIMIT_LC=0,5
LIMIT_LM=0,5
LIMIT_LK=0,5
LIMIT_LLK=0,5

N_OF_UNUSED=0

CURVE_K="0;0 50;90 100;100"
CURVE_LK="0;0 50;90 100;100"
CURVE_LLK="0;0 50;90 100;100"
CURVE_C="0;0 50;90 100;100"
CURVE_M="0;0 50;90 100;100"
CURVE_Y="0;0 50;90 100;100"
CURVE_LC="0;0 50;90 100;100"
CURVE_LM="0;0 50;90 100;100"

With boost, Testboost3.txt file:

N_OF_INKS=8
DEFAULT_INK_LIMIT=

LIMIT_K=20
BOOST_K=30
LIMIT_C=20
LIMIT_M=20
LIMIT_Y=20
LIMIT_LC=0,5
LIMIT_LM=0,5
LIMIT_LK=0,5
LIMIT_LLK=0,5

N_OF_UNUSED=0

CURVE_K="0;0 50;90 100;100"
CURVE_LK="0;0 50;90 100;100"
CURVE_LLK="0;0 50;90 100;100"
CURVE_C="0;0 50;90 100;100"
CURVE_M="0;0 50;90 100;100"
CURVE_Y="0;0 50;90 100;100"
CURVE_LC="0;0 50;90 100;100"
CURVE_LM="0;0 50;90 100;100"

Re: [QuadtoneRIP] Re: Boost K

2016-08-11 by richard@...

This is what I expected. The individual ink curve settings at the bottom are overriding the boost setting. 

For the boost setting to work you need to let QTR build the gray curve using at least one partitioned gray ink (usually K). 

With your ink curves the 100;100 point is being mapped to your limit, and all the gray curve stuff is being ignored/overridden. If you want to make the 100;100 point be 30 like your boost setting but everything else be the same as it is now, you need to open the .quad file in a text editor, go down to the lay number directly above # C Curve and change it to 19660.  (Which is just 0.3 * 65535 instead of 0.2 * 65535 )

RB

Re: [QuadtoneRIP] Boost K

2016-08-11 by Stefan Christiansen

I won't go into partitioning, my ink set is not designed for that.
Modifying the .quad file is the route I will go.
Thanks for showing it.


Stefan Christiansen

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