> Howard
>
> I plotted your density values to have a look and the values are fairly
> linear (i.e. they are fairly far from the LAB curve). One thing you might
> try is to increase the gamma value of the gray curve. I'm not sure if you've
> changed it yet, but assuming it's at its default value of 1, you could try
> something in the 1.5 to 2 range. That would bring the curve closer to the
> target LAB values before linearizing and might make it easier for the
> linearizer to work its magic.
>
> I'm not sure what others do, but I go through several iterations for each
> curve adjusting the highlight, shadow and gamma values to bring the curve as
> close as I can (reasonably close anyway) to LAB, before linearizing. The
> curveeval spreadsheet I posted makes it convenient to save and plot curves
> over several iterations and gives you a sense for the effect of changing
> values. It's set up for the 21 step wedge, but that's a lot more convenient
> to use until you get the curve close anyway.
>
> At some point early on with QTR Roy told me that it was better to bring the
> curve closer to the target profile using the shadow and highlight (and gamma
> if necessary). This way the linearization would be a small adjustment of the
> curve rather than a major move. I've not seen much discussion of this
> recently, but I still do it out of habit. It's fairly quick once you get a
> feel for what the numbers do. The main thing to remember is that larger
> numbers make the density curve lower. That's true for all three values,
> although the gamma changes have larger effect.
>
> Tom Moore
>
> > -----Original Message-----
> > From: QuadtoneRIP@yahoogroups.com [mailto:QuadtoneRIP@yahoogroups.com] On
> > Behalf Of Howard Shaw
> > Sent: Friday, October 28, 2005 12:12 PM
> > To: QuadtoneRIP@yahoogroups.com
> > Subject: Re: [QuadtoneRIP] Error message: Invalid linearize curve - not
> > constantly increasing
> >
> > I have ink limit at 90%, boost at 95%, shadow at 12 & overlap at 16. The
> > paper is Permajet Alpha. The limit is quite high so I'm not sure how
> > much effect black boost is having anyway. I chose the high limit as the
> > dmax was at its greatest (1.72 absolute) on the 90% patch.
> >
> > I'm using x-rite 810 for measurements and I've re-checked them and they
> > are consistent.
> >
> > I'll have a play around with reducing the boost & the overlap as I don't
> > seem to get quite the dmax I did on the calibration strip.
> >
> > Howard
> >
> >
> >
> >
> >
> > John Moody wrote:
> > > The last step has a much higher density increase than all others,
> > > effectively asking the linearization to fix a sharp bend at the end of
> > > the curve.
> > >
> > > Do you have black boost at a fairly high level? If so, you may get
> > > smoother results cutting back on black-boost, and upping the ink limit
> > > to achieve the 1.69 Dmax you are getting. A high shadow value can bend
> > > the curve like that as well, but since it's only the last step, I'm
> > > guessing black boost.
> > >
> > > Also, if you scanned the patches with an i1, you might go back and
> > > re-read the last several in patch mode to see that you get consistent
> > > values. I have a hypothesis that the dark patch accuracy degrades with
> > > increasing scan speed, but I have not seen others corroborate that.
> > >
> > >
> > >
> > > Best regards,
> > >
> > > John Moody
> > >
> > >
> > >
> > > -----Original Message-----
> > > *From:* QuadtoneRIP@yahoogroups.com
> > > [mailto:QuadtoneRIP@yahoogroups.com]*On Behalf Of *Howard Shaw
> > > *Sent:* Thursday, October 27, 2005 5:51 PM
> > > *To:* QuadtoneRIP@yahoogroups.com
> > > *Subject:* [QuadtoneRIP] Error message: Invalid linearize curve - not
> > > constantly increasing
> > >
> > >
> > >
> > > I was making a linearisation today with the following values from a
> > > 51-step and got the above error message and the curve was not created:
> > > 0.06
> > > 0.08
> > > 0.1
> > > 0.12
> > > 0.15
> > > 0.17
> > > 0.2
> > > 0.23
> > > 0.26
> > > 0.29
> > > 0.33
> > > 0.36
> > > 0.41
> > > 0.45
> > > 0.48
> > > 0.53
> > > 0.57
> > > 0.61
> > > 0.65
> > > 0.69
> > > 0.72
> > > 0.75
> > > 0.79
> > > 0.83
> > > 0.87
> > > 0.91
> > > 0.95
> > > 0.98
> > > 1.01
> > > 1.04
> > > 1.09
> > > 1.12
> > > 1.14
> > > 1.18
> > > 1.19
> > > 1.22
> > > 1.24
> > > 1.28
> > > 1.31
> > > 1.34
> > > 1.37
> > > 1.4
> > > 1.42
> > > 1.46
> > > 1.49
> > > 1.52
> > > 1.55
> > > 1.57
> > > 1.6
> > > 1.62
> > > 1.69
> > >
> > > All the values are increasing albeit not "constantly". If I change the
> > > penultimate value from 1.62 to 1.63 the curve creation works. Any
> reason
> > > this should be so?
> > >
> > > Howard
>