Examine my process and give me advice (very detailed example of partitioning)
2007-05-04 by James Haney
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
[Non-text portions of this message have been removed]