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help! linearization kills dmax

help! linearization kills dmax

2007-06-18 by Daniel Jackson

I'm trying to create a simple QTR curve. When I linearize it, I do
indeed get a much straighter luminance curve, but the dmax at
100% drops dramatically: when plotted in Excel, the curve 
noticeably tips upwards between 95 and 100, reducing the
dmax from 1.62 pre-linearization to 1.53 after.

Why is this happening and how do I fix it? 

--Daniel
PS. Gray overlap is set to zero, so I don't think it's related to the
second ink curve being changed.

Re: [QuadtoneRIP] help! linearization kills dmax

2007-06-18 by Roy Harrington

Hi Daniel,

100% black should stay 100% black in the output.   The most likely reasons for
this not working correctly is the Rendering Intent and Black Point Compensation.
In Photoshop it definitely has to be Perceptual Intent and BPC=On.  Relative
Colormetric often gives reduced dMax.  On Mac's it's simply on the
Print with Preview
page.  But if you use Convert-to-Profile check there as well.  Default
is often set
at Relative.  If you are on a PC and use other editing programs --
Qimage in particular -
it's important to see how it works.

Ernst just mentioned some issues with Qimage so see that thread as well.

Roy
Show quoted textHide quoted text
On 6/18/07, Daniel Jackson <dnj@...> wrote:
> I'm trying to create a simple QTR curve. When I linearize it, I do
> indeed get a much straighter luminance curve, but the dmax at
> 100% drops dramatically: when plotted in Excel, the curve
> noticeably tips upwards between 95 and 100, reducing the
> dmax from 1.62 pre-linearization to 1.53 after.
>
> Why is this happening and how do I fix it?
>
> --Daniel
> PS. Gray overlap is set to zero, so I don't think it's related to the
> second ink curve being changed.
>
>

Re: help! linearization kills dmax

2007-06-20 by Daniel Jackson

Roy,

The post-linearization measurement is of the 21-step target, and I'm printing
it with color management off. 

Am I supposed to turn it on after linearization? And if so, how do I select
an appropriate ICC profile?

--Daniel

--- In QuadtoneRIP@yahoogroups.com, "Roy Harrington" <roy@...> wrote:
Show quoted textHide quoted text
>
> Hi Daniel,
> 
> 100% black should stay 100% black in the output.   The most likely reasons for
> this not working correctly is the Rendering Intent and Black Point Compensation.
> In Photoshop it definitely has to be Perceptual Intent and BPC=On.  Relative
> Colormetric often gives reduced dMax.  On Mac's it's simply on the
> Print with Preview
> page.  But if you use Convert-to-Profile check there as well.  Default
> is often set
> at Relative.  If you are on a PC and use other editing programs --
> Qimage in particular -
> it's important to see how it works.
> 
> Ernst just mentioned some issues with Qimage so see that thread as well.
> 
> Roy
> 
> 
> On 6/18/07, Daniel Jackson <dnj@...> wrote:
> > I'm trying to create a simple QTR curve. When I linearize it, I do
> > indeed get a much straighter luminance curve, but the dmax at
> > 100% drops dramatically: when plotted in Excel, the curve
> > noticeably tips upwards between 95 and 100, reducing the
> > dmax from 1.62 pre-linearization to 1.53 after.
> >
> > Why is this happening and how do I fix it?
> >
> > --Daniel
> > PS. Gray overlap is set to zero, so I don't think it's related to the
> > second ink curve being changed.
> >
> >
>

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