QTR-Quadtone RIP

>
> I am having a big problem trying to create a profile for Epson Premium Photo Gloss.
> 
> Every time I set an ink limit, regardless of value, when it comes to measure a 21 step wedge for linearisation, I find that the last two (darkest value) steps appear to have lower density values than the lighter steps.
> 
> It seems that somehow there is a feedback problem within the process I am using, but I can't imagine where this may be.
> 
> For example:
> 
> Printing out the inkseparation6.tiff file via QTR print, with no color management I measured density values which indicated an ink limit of 75%.  I then reprinted the inksearation6.tiff to calcualate the gray value, which was 35%.  I was using Cyan, Cool Photo black and Light Cyan, Dilute cool photo black, to get a cool profile.  
> 
> I then install the profile, without linearisation details.  Next, when printing a 21 step wedge to linearise the profile, I then find that the maximum density value is about 90% and declines for the next two steps.  I have repeated all these steps several times and have even gone down to an ink limit of 45%.  However every time I've tried to create a linearisation file I find that the darkest steps have a density value lower than 90%, which seems to have the maximum value.
> 
> The advice from tutorials suggests to set the ink limit at the point where the initial density values reach a maximum. I.e. if the measured density values are 2.00 at 60%, 2.01 at 65% 2.01 at 70%, then 65% should be the set ink value.  Initially I followed this procedure to set the max ink value.  I now think that instead of aiming for the maximum density value, I should go for the maximum density value reached by steps of .02 instead of 0.01. so if the steps go up such as, 2.00 for 50%, 2.04 for 55%, 2.05 for 60%, 2.06 for 65%, 2.07 for 70% 2.08 for 75%, I should set the ink limit at 60% and no higher.  However, following this rule, when it comes to linearisation, I find that the top one or two density values are still lower than 90 or 95%.
> 
> 
> It is getting beyond frustration point now.  I think the next step is to remove all programmes and start afresh.  I seem unable to get to the point of linearisation, so would appreciate any help.
> 
> Ross
>

>
> rossfmj  wrote:
> 
> > **
> >
> >
> > I am having a big problem trying to create a profile for Epson Premium
> > Photo Gloss.
> >
> > Every time I set an ink limit, regardless of value, when it comes to
> > measure a 21 step wedge for linearisation, I find that the last two
> > (darkest value) steps appear to have lower density values than the lighter
> > steps. ...
> >
> Be sure to read http://www.paulroark.com/BW-Info/UT14.pdf
> 
> Note that the K position is matte black, not glossy photo black.
> 
> The C and M inks are types of PK.  They are what you are going to use to
> generate the black, not the MK that is in the K position.
> 
> I'm guessing that is what is going on.
> 
> The LC and LM are Lk-density inks.
> 
> To the extent it is consistent with the tones you want to achieve, use C,
> M, LC and LM.  You can make a cool and a warm profile and mix them with the
> sliders.
> 
> I hope this helps.
> 
> Paul
> www.PaulRoark.com
> 
> 
> [Non-text portions of this message have been removed]
>

>
> Ross,
>    Your ink limits sound high to me.  I've not used the Epson Premium Photo Gloss, but for the glossy papers that I have profiled, the ink limits were 25-35%.  
> 
> One thing that I do is to print the ink separation file with a 50% ink limit, so that more of the steps provide useful information, and then include this factor in setting the limit. 
> 
> David
> 
> --- In QuadtoneRIP@yahoogroups.com, "rossfmj"  wrote:
> >
> > I am having a big problem trying to create a profile for Epson Premium Photo Gloss.
> > 
> > Every time I set an ink limit, regardless of value, when it comes to measure a 21 step wedge for linearisation, I find that the last two (darkest value) steps appear to have lower density values than the lighter steps.
> > 
> > It seems that somehow there is a feedback problem within the process I am using, but I can't imagine where this may be.
> > 
> > For example:
> > 
> > Printing out the inkseparation6.tiff file via QTR print, with no color management I measured density values which indicated an ink limit of 75%.  I then reprinted the inksearation6.tiff to calcualate the gray value, which was 35%.  I was using Cyan, Cool Photo black and Light Cyan, Dilute cool photo black, to get a cool profile.  
> > 
> > I then install the profile, without linearisation details.  Next, when printing a 21 step wedge to linearise the profile, I then find that the maximum density value is about 90% and declines for the next two steps.  I have repeated all these steps several times and have even gone down to an ink limit of 45%.  However every time I've tried to create a linearisation file I find that the darkest steps have a density value lower than 90%, which seems to have the maximum value.
> > 
> > The advice from tutorials suggests to set the ink limit at the point where the initial density values reach a maximum. I.e. if the measured density values are 2.00 at 60%, 2.01 at 65% 2.01 at 70%, then 65% should be the set ink value.  Initially I followed this procedure to set the max ink value.  I now think that instead of aiming for the maximum density value, I should go for the maximum density value reached by steps of .02 instead of 0.01. so if the steps go up such as, 2.00 for 50%, 2.04 for 55%, 2.05 for 60%, 2.06 for 65%, 2.07 for 70% 2.08 for 75%, I should set the ink limit at 60% and no higher.  However, following this rule, when it comes to linearisation, I find that the top one or two density values are still lower than 90 or 95%.
> > 
> > 
> > It is getting beyond frustration point now.  I think the next step is to remove all programmes and start afresh.  I seem unable to get to the point of linearisation, so would appreciate any help.
> > 
> > Ross
> >
>

>
> Dave, thanks again
> 
> I'd noticed how high my ink limits were, particularly in relation to those in your own profiles, however these are the figures I'm currently getting at the calibration stage.  I've also been setting an initial calibration value of 50% (depending on circumstances), but I've had to use a higher value for this paper combination, due to the high numbers I'm getting.
> 
> See my post in reply to Paul regarding some of my thoughts on this.
> 
> I'm now wondering if the inkseparation image and 21step images have had their colour space overwritten by Elements, and that's causing issues.  I've now trashed QTR and done a clean install to refresh the files, maybe that'll improve things.  I have now moved to using QTR print for these images as this allows printing with no colour management.  Adobe and Apple between them have made this practically impossible through Elements.  I think Elements also has the habit of overwriting unrecognised colour space on opening images.  I thought I'd prevented this up to now but maybe hadn't.
> 
> Ross
> 
> --- In QuadtoneRIP@yahoogroups.com, "David"  wrote:
> >
> > Ross,
> >    Your ink limits sound high to me.  I've not used the Epson Premium Photo Gloss, but for the glossy papers that I have profiled, the ink limits were 25-35%.  
> > 
> > One thing that I do is to print the ink separation file with a 50% ink limit, so that more of the steps provide useful information, and then include this factor in setting the limit. 
> > 
> > David
> > 
> > --- In QuadtoneRIP@yahoogroups.com, "rossfmj"  wrote:
> > >
> > > I am having a big problem trying to create a profile for Epson Premium Photo Gloss.
> > > 
> > > Every time I set an ink limit, regardless of value, when it comes to measure a 21 step wedge for linearisation, I find that the last two (darkest value) steps appear to have lower density values than the lighter steps.
> > > 
> > > It seems that somehow there is a feedback problem within the process I am using, but I can't imagine where this may be.
> > > 
> > > For example:
> > > 
> > > Printing out the inkseparation6.tiff file via QTR print, with no color management I measured density values which indicated an ink limit of 75%.  I then reprinted the inksearation6.tiff to calcualate the gray value, which was 35%.  I was using Cyan, Cool Photo black and Light Cyan, Dilute cool photo black, to get a cool profile.  
> > > 
> > > I then install the profile, without linearisation details.  Next, when printing a 21 step wedge to linearise the profile, I then find that the maximum density value is about 90% and declines for the next two steps.  I have repeated all these steps several times and have even gone down to an ink limit of 45%.  However every time I've tried to create a linearisation file I find that the darkest steps have a density value lower than 90%, which seems to have the maximum value.
> > > 
> > > The advice from tutorials suggests to set the ink limit at the point where the initial density values reach a maximum. I.e. if the measured density values are 2.00 at 60%, 2.01 at 65% 2.01 at 70%, then 65% should be the set ink value.  Initially I followed this procedure to set the max ink value.  I now think that instead of aiming for the maximum density value, I should go for the maximum density value reached by steps of .02 instead of 0.01. so if the steps go up such as, 2.00 for 50%, 2.04 for 55%, 2.05 for 60%, 2.06 for 65%, 2.07 for 70% 2.08 for 75%, I should set the ink limit at 60% and no higher.  However, following this rule, when it comes to linearisation, I find that the top one or two density values are still lower than 90 or 95%.
> > > 
> > > 
> > > It is getting beyond frustration point now.  I think the next step is to remove all programmes and start afresh.  I seem unable to get to the point of linearisation, so would appreciate any help.
> > > 
> > > Ross
> > >
> >
>

> OK.  The next thing to consider is that an LK density ink will often
> actually have a higher dmax than PK.  But, it will do so with such a high
> load that the paper will be too wet, causing other problems, like increased
> pizza wheel marks.
> 
> So, measure the LC (a neutral LK) densities on the 100% calibration mode
> print and set an ink limit for the LC that is such that the density is
> about 50% of the PK ink limit density.  This should stop the combined LC +
> C from being higher than the C density at it's dmax.
> 
> Basically, you may need a much lower ink limit on the LC.
> 
> Paul
> www.PaulRoark.com
> 
> 
> [Non-text portions of this message have been removed]
>

>
> Ross,
>     As an example, I have just uploaded an image of a graph of densities I measured with UT-14 cyan on Ilford GFS:
> 
> http://groups.yahoo.com/group/QuadtoneRIP/photos/album/499015501/pic/list
> 
> These were printed with a 50% ink limit, but the numbers on the horizontal axis are corrected to a maximum of 100%.  As shown in the graph, there is a nice smooth increase up to about 32% ink density, and then a more erratic increase.  In my experience, it is counter productive to try to use anything beyond the smooth part of the curve.
> 
> David

>
> Thanks David, that's been very helpful, I've now made a chart and can see what you mean.  I'll try and post the chart.
> 
> I think I made the mistake of chasing the numbers way beyond any useful limit and picked the high point of the curve, a fair way along the section with little increasing value.  Looking at the chart I can see the useful point should be around the 30%-40% mark.  I'll set to this and see where it gets me.
> 
> Ross
> 
> --- In QuadtoneRIP@yahoogroups.com, "David"  wrote:
> >
> > Ross,
> >     As an example, I have just uploaded an image of a graph of densities I measured with UT-14 cyan on Ilford GFS:
> > 
> > http://groups.yahoo.com/group/QuadtoneRIP/photos/album/499015501/pic/list
> > 
> > These were printed with a 50% ink limit, but the numbers on the horizontal axis are corrected to a maximum of 100%.  As shown in the graph, there is a nice smooth increase up to about 32% ink density, and then a more erratic increase.  In my experience, it is counter productive to try to use anything beyond the smooth part of the curve.
> > 
> > David
>