QTR-Quadtone RIP

Hi James

One thing I noticed is that your unlinearised stepwedge in step 11 is 
some way from optimum. It gets dark too quickly leaving the 70-100 
shadow areas very compressed. I appreciate that after linearisation you 
are only having problems in the 95-100 range but, if it were me, I would 
be looking to get the initial partitions closer to ideal.

You're using a 50% ink limit and I would hazard a guess that you are 
using a resolution of 2880dpi although you haven't told us that. I would 
try a lower ink limit to get those deeper black values more spread out.

I've not looked at how you've done the partitions but there is 
discussion previously on the list that should help with that.

regards
Howard

--
Howard Shaw
glassman@...
www.howardshaw.org

James Haney wrote:
> I am having a challenge.
> 
> I am in the process of re-creating a set of curves due to some  
> changes in density after a recent service call.
> 
> I have traditionally had difficulty overcoming the below-explained  
> issue but have either dealt with it or "tweaked" around it.
> 
> 
> 
> 
> Bear with me, this is a lot of detail but I think it would be a good  
> exercise to document this for public consumption.
> 
> 
> I am creating two curves, using Cone Piezotone inks.
> Each curve will be a partition of 4 inks
> 
> Carbon Sepia Curve: Museum Black, Carbon Sepia Dark, Carbon Sepia  
> Medium, Carbon Sepia Light
> 
> Selenium Tone Curve: Museum Black, Selenium Tone Dark, Selenium Tone  
> Medium, Selenium Tone Light
> 
> 
> Environment:
> 	- Mac OSX 10.4.8
> 	- QTR version 2.5
> 
> 	- Photoshop CS2
> 
> 	- Epson 7600
> 		Piezotone inks
> 			Museum Black
> 			Carbon Sepia set
> 			Selenium set.
> 
> 	- Hahnemuhle Photo Rag 308
> 
> 
> Process:
> 1) Print the InkSeparation.psd file
> 	No color management when opening
> 	No color management when printing
> 	Printed in Calibration mode
> 	Calibration Ink Density 100%
> 
> 2) Dry the print
> 
> 3) Find the first point in Black scale where we reach total ink  
> coverage.
> 	Visually and with a Densitometer
> 	I determined the Default Ink Density should be 50% (Density 1.7 read  
> with Xrite 810)
> 
> 4) Reprint the InkSeparation.psd file with same settings except  
> Calibration Ink Density set to 50%
> 
> 5) Dry Print
> 
> 6) Determine partitioning values for ink overlap for
> 	a) Point where 100% density of Carbon Sepia Dark intersects with  
> ramp of Museum Black
> 	b) Point where 100% density of Carbon Sepia Medium intersects with  
> ramp of Carbon Sepia Dark
> 	b) Point where 100% density of Carbon Sepia Light intersects with  
> ramp of Carbon Sepia Medium
> 
> 
> The following table displays densitometer reading of every patch.
> 
> Ink 1 - Black - Unlimited    00     05    10    15    20    25     
> 30    35    40    45    50    55    60    65    70    75    80     
> 85    90    95    100
> Museum Black - Unlimited    0.05   0.54  0.88  1.13  1.34  1.48   
> 1.56  1.61  1.66  1.68  1.70  1.71  1.72  1.72  1.73  1.73  1.73   
> 1.72  1.71  1.71  1.72
> 
>      Reprint with Calibration Ink Limit set at 50%
> 
>      Readings from resulting print:
> 
> Ink - 1 Black (limited)  0     5    10    15    20    25    30     
> 35    40    45    50    55    60    65    70    75    80    85     
> 90    95    100   Overlap   Calculated values
> Museum Black (40%)      0.05 0.33  0.54  0.74  0.91  1.02  1.12   
> 1.25  1.35  1.44  1.49  1.53  1.57  1.60  1.62  1.65  1.66  1.68   
> 1.68  1.69  1.70   100.0%      100.0%
> 
> Ink 2 - Cyan             0     5    10    15    20    25    30     
> 35    40    45    50    55    60    65    70    75    80    85     
> 90    95    100
> Carbon Sepia Dark       0.05  0.18  0.29  0.39  0.48  0.56  0.63   
> 0.70  0.77  0.84  0.89  0.95  1.00  1.04  1.08  1.13  1.15  1.20   
> 1.23  1.26  1.28   36.5%      36.50%
> 
> Ink 3 - Magenta          0     5    10    15    20    25    30     
> 35    40    45    50    55    60    65    70    75    80    85     
> 90    95    100
> Carbon Sepia Med        0.05  0.11  0.15  0.20  0.24  0.27  0.32   
> 0.35  0.40  0.44  0.47  0.50  0.54  0.57  0.60  0.62  0.66  0.68   
> 0.70  0.73  0.75   38.0%      13.87%
> 
> Ink 4 - Yellow           0     5    10    15    20    25    30     
> 35    40    45    50    55    60    65    70    75    80    85     
> 90    95    100
> Selenium Light          0.05  0.08  0.09  0.11  0.13  0.14  0.16   
> 0.18  0.20  0.22  0.24  0.26  0.27  0.29  0.30  0.32  0.33  0.35   
> 0.36  0.38  0.38   48.0%       4.92%
> 
> Ink 5 - Light Cyan       0     5    10    15    20    25    30     
> 35    40    45    50    55    60    65    70    75    80    85     
> 90    95    100
> Selenium Dark           0.05  0.16  0.23  0.31  0.38  0.45  0.51   
> 0.58  0.64  0.69  0.74  0.79  0.83  0.87  0.90  0.93  0.97  1.00   
> 1.02  1.04  1.07   27.0%      27.00%
> 
> Ink 6 - Light Magenta    0     5    10    15    20    25    30     
> 35    40    45    50    55    60    65    70    75    80    85     
> 90    95    100
> Selenium Med            0.05  0.10  0.13  0.17  0.20  0.23  0.27   
> 0.30  0.33  0.36  0.39  0.42  0.44  0.47  0.49  0.51  0.54  0.56   
> 0.58  0.60  0.62   38.0%      10.26%
> 
> Ink 1 - Light Black      0     5    10    15    20    25    30     
> 35    40    45    50    55    60    65    70    75    80    85     
> 90    95    100
> Carbon Sepia Light     0.05  0.08  0.10  0.12  0.14  0.17  0.19   
> 0.22  0.23  0.26  0.28  0.30  0.32  0.34  0.35  0.38  0.40  0.42   
> 0.43  0.44  0.46    48.0%       6.66%
> 
> 
> 7) Create a new Ink Descriptor file for Museum Black plus the three  
> Carbon Sepia inks
>     - I am not currently at the computer that has the file on it to  
> include all of the data, but I inserted the proper VAL= entries in  
> the proper inks.
> 
>     For reference I used the following other values
> 
>     GRAY_HIGHLIGHT=10
>     GRAY_SHADOW=10
> 
>     GRAY_OVERLAP=
>     GRAY_GAMMA=1
>     GRAY_CURVE=
> 
> 8) Created curve via "Drop-Quad-Profile"
> 
> 9) Print a 21 Step file
> 	- Opened without color managing
> 	- Printed without color management
> 	- Selected the proper Curve file
> 	- Made sure I was using 100% of the curve
> 	- No other curves were selected
> 
> 10) Dry Print
> 
> 11) Read 21 patches from resulting print
> 
>      Readings shown below
> 
>        0    05    10    15    20    25    30    35    40    45     
> 50    55    60    65    70    75    80    85    90    95    100
>      0.05  0.33  0.54  0.74  0.91  1.02  1.12  1.25  1.35  1.44   
> 1.49  1.53  1.57  1.60  1.62  1.65  1.66  1.68  1.68  1.69  1.70
> 
> 
>      Notice the flat spot between 85% and 95%
> 
>      These values prevent a successful linearization
> 
> 
> 11) Just for grins I "tweaked" the 85% reading to 1.67 to create  
> enough difference to process the linearization.
> 
> 
> 12) Print a 21 Step file
> 	- Opened without color managing
> 	- Printed without color management
> 	- Selected the proper Curve file
> 	- Made sure I was using 100% of the curve
> 	- No other curves were selected
> 
>     (Should I be choosing a document profile and a Printer Profile  
> here?)
> 
> 12) Analyze print
> 
> 	The result was unacceptable.
> 	Everything looks great except between 95 and 100% there is a sudden,  
> hard drop to max density
> 
> 
> 13) I re-did the Linearization process using an Eye-One with the 51- 
> Step-Random file and MeasureTool
>      I kept getting "Linearization failed - values do not..." (I  
> can't recall the exact verbiage, but you know the one.)
>      I opened the file in Excel and did some hunting.
>      I sorted the data by L-density and found two lines that seemed  
> out of whack
> 
> 14) I re-read the values from the print again to rule out user error  
> in the patch-reading process.
>      Again, I got the "Linearization failed - values do not..." error
>      I opened this new file in Excel.
>      I sorted the data by L-density and this time found FOUR lines  
> that were out of whack (not the same ones as the first time)
> 
> 15) I decided to try to "tweak" the density L values in the first  
> file to make them conform and got the "QTR-Linearize-Data" process to  
> work.
> 	I then dropped the file on "QTR-Create-ICC" and successfully created  
> a profile
> 
> 16) I printed the 21 step file, choosing my freshly minted profile.
>      This time everything looked very good.
> 
> Sooooo....
> 
> 17) I followed the same Eye-one Process for Museum Black and the  
> three Selenium inks
>      New Print of 51 step Random
> 	Dry Print
> 	Read in MeasureTool
> 	Save file
> 	Drop on "QTR-Linearize-Data"
> 	Again, I got the "Linearization failed - values do not..." error
> 	However, when I opened the file in Excel to analyze, I noticed that  
> the value for 100% was quite a bit different than the 95% patch. So  
> different that I cannot tweak it in good conscience.
> 
> Given that the highest density of the darkest Selenium ink is 1.07  
> versus 1.28 for the darkest Carbon Sepia, should I set the ink limit  
> for the Selenium inks to 100% and re-partition, or is there an error  
> somewhere in my process?
> 
> Any advice is gladly accepted.
> 
> James Haney
> 
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