QTR-Quadtone RIP

Need some help here. Creating a bunch of curves and have gotten the above message when trying to install a handful of them.
In a couple, there are a pair of steps with identical density. The solution for that suggests itself: remeasure or start over.
But on the rest, there IS a "constant increase". What do I do there? Is there a minimal step the software is looking for, such that it would call say, 45.55 and 45.58 the same density and therefore declare those two steps as "not constantly increasing"?
What should I be looking for in general in these numbers? I don't see any documentation on this anywhere. (I am very well acquainted with densities and curves for traditional analog materials, but don't quite know what I am looking for here.)

dk

There is a minimum increase between steps that is needed.  Where you have a
problem like this, it indicates that something in the original ink setup
needs tweaking.

Paul
www.PaulRoark.com


On Wed, Aug 14, 2013 at 5:17 PM, davidkachel <david@...> wrote:

> **
>
>
> Need some help here. Creating a bunch of curves and have gotten the above
> message when trying to install a handful of them.
> In a couple, there are a pair of steps with identical density. The
> solution for that suggests itself: remeasure or start over.
> But on the rest, there IS a "constant increase". What do I do there? Is
> there a minimal step the software is looking for, such that it would call
> say, 45.55 and 45.58 the same density and therefore declare those two steps
> as "not constantly increasing"?
> What should I be looking for in general in these numbers? I don't see any
> documentation on this anywhere. (I am very well acquainted with densities
> and curves for traditional analog materials, but don't quite know what I am
> looking for here.)
>
> dk
>
>  
>


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

From:  Paul Roark

There is a minimum increase between steps that is needed. Where you have a
problem like this, it indicates that something in the original ink setup
needs tweaking.

What is that minimum increase and what kind of tweaking in the original ink
setup?


David Kachel

___________________

Artist-Photographer
Fine B&W Photographs

www.davidkachel.com
david@...

Gallery:
www.reddoorfinephotographs.com
director@...

PO Box  1893
Alpine, TX 79831
(432) 386-5787




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

I forget the minimum, but if you graph the Lab L you'll probably be able to
see where the problem is.  You can compare the Lab L glitch with the graph
of the cross-overs and usually see what ink may need it's ink limit raised
or lowered.

Paul
www.PaulRoark.com


On Wed, Aug 14, 2013 at 5:51 PM, David Kachel <david@...> wrote:

> **
>
>
> From: Paul Roark
>
> There is a minimum increase between steps that is needed. Where you have a
> problem like this, it indicates that something in the original ink setup
> needs tweaking.
>
> What is that minimum increase and what kind of tweaking in the original ink
> setup?
>
> David Kachel
>
> ___________________
>
> Artist-Photographer
> Fine B&W Photographs
>
> www.davidkachel.com
> david@...
>
> Gallery:
> www.reddoorfinephotographs.com
> director@reddoorfinephotographs.com
>
> PO Box 1893
> Alpine, TX 79831
> (432) 386-5787
>
> [Non-text portions of this message have been removed]
>
>  
>


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

The 'minimum increase between steps" that Paul refers to is apparently quite large. After numerous trials to get the "Linearize Data" routine to take my curves, I gave up. 
Instead, I print without linearization, measure the 21 step tablet, plug resulting L* values into excel increasing as %K increases (or highest L value to lowest), then type those values into the Curve at "LINEARIZE=" step, save the curve and install it, then reprint, remeasure, and import  L* values into Excel to measure linearity. Never fails to give me a linear curve. 

If I see that the non-linearized graph of L* values has large bumps or irregular internal slopes, I do have to go back and adjust the ink values. It doesn't have to be straight, but it should be regular (read this to mean without erratic slopes). My setup requires that I use much less LK than most of the sample curves (or the Calibration curve) suggest, so don't hesitate to experiment with the Gray_values for your intermediate blacks.

Good luck.

Jim

I was recently getting the same error message in working up a curve for Eboni6 and Epson Hot Press Bright, with a resulting graph that was anything but linear. I had been attempting to print through Photoshop CS5 with color management turned off. The solution turned out to be simple - QTR Print Tool. If you are not already using it to generate the ink separation print that might be an easy fix.

- Jan



--- In QuadtoneRIP@yahoogroups.com, David Kachel <david@...> wrote:

>
> From:  Paul Roark
> 
> There is a minimum increase between steps that is needed. Where you have a
> problem like this, it indicates that something in the original ink setup
> needs tweaking.
> 
> What is that minimum increase and what kind of tweaking in the original ink
> setup?
> 
> 
> David Kachel
> 
> ___________________
> 
> Artist-Photographer
> Fine B&W Photographs
> 
> www.davidkachel.com
> david@...
> 
> Gallery:
> www.reddoorfinephotographs.com
> director@...
> 
> PO Box  1893
> Alpine, TX 79831
> (432) 386-5787
> 
> 
> 
> 
> [Non-text portions of this message have been removed]
>

From:  janbecket 

"I was recently getting the same error message in working up a curve for
Eboni6 and Epson Hot Press Bright, with a resulting graph that was anything
but linear. I had been attempting to print through Photoshop CS5 with color
management turned off. The solution turned out to be simple - QTR Print
Tool. If you are not already using it to generate the ink separation print
that might be an easy fix."

Thanks.
I finally got it squared away.  I needed more careful measurement (those
squares are tiny!) and to reduce my max point by 5 points on one of them.

David Kachel

___________________

Artist-Photographer
Fine B&W Photographs

www.davidkachel.com
david@...

Gallery:
www.reddoorfinephotographs.com
director@...

PO Box  1893
Alpine, TX 79831
(432) 386-5787





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