Digital BW, The Print

Hi Didzis,

 

>The 51-step wedge might just be the answer.

> the resulting ICC is better in terms of dark tones separation. . 

 

I was just pondering the easiest way to accomplish this goal.  The problem
is, I suspect, that the 95 - 100%  black ramps are not very linear.  The
responses of the ink-paper combinations become very non-linear there.  But
our 21-step curves just don't have the information in them that is needed.
This makes Create ICC just assume something - probably linear or a smooth
exponential curve - and that assumed ink response is just not close enough
to what we're actually getting. 

 

Good 51-step test strips give more data points there.  Some of the high end
rips have even more test patches.

 

The very large test strips, however, are not the easy to use with desktop
printers and spectros that are not strip readers.  Roller marks and other
problems distort the information.  I found that vertical printing helps.
Unfortunately, a letter size sheet is not enough room for a straight line of
51 test patches large enough to read.  If there are 2 columns, then one has
to watch out for a difference introduces by a roller. 

 

I use a 21-step but then also do a 90-100% 1% test strip.  In fact, I do it
as part of setting up a printer.  It helps me nail the dmax.  

See http://www.paulroark.com/BW-Info/Fine%20Tuning%20the%20Dmax.pdf  

 

I've found the highlights and even midtones (with the workflows I mostly use
now) are usually not a problem.  There I think the 5% steps of the 21-step
test strip are enough. 

 

I'm not sure where the "sweet spot" is in terms of time and effort,
cost-benefit with respect to the darkest 5%.  If the dmax is "correctly" set
by the original profile, or the ink matches the existing driver assumptions
(testing the 260 at the moment), then it may be that the 21-steps is enough.
However, I think that some of the older profiles with steep cross-overs and
curves may be sensitive to printer and inkset variations.  

 

Paul

www.PaulRoark.com <http://www.paulroark.com/>  

 

 

 

 

  _____  

From: DigitalBlackandWhiteThePrint@yahoogroups.com
[mailto:DigitalBlackandWhiteThePrint@yahoogroups.com] On Behalf Of dizpark
Sent: Sunday, September 09, 2007 1:57 PM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] create-icc problem

 

Hi, Paul!

> >I will give the 51-step wedge a try. Can I use the one that is 
> >included with the Quadtone RIP Eye-One folder?
> 
> It's worth a try. I recommend printing vertically and in the 
middle of the
> page. Try to avoid any area that is going to be touched with a 
roller.
> 

The 51-step wedge might just be the answer. I used the one that is 
in the eye-one folder and I believe the resulting ICC is better in 
terms of dark tones separation. I made an ICC from the carbon curve. 
Then I printed your grey gamma 2.2 21-step wedge using this ICC.

Here are the figures.

96.73 0.94 -0.44
92.77 1.21 1.14
88.23 1.56 2.86
83.90 1.88 4.38
80.10 2.07 5.42
75.68 2.35 6.34
71.21 2.54 6.91
66.93 2.69 7.26
62.71 2.78 7.53
58.27 2.92 7.50
53.77 2.90 7.36
48.58 2.74 6.74
43.84 2.50 5.84
39.09 2.20 4.19
34.31 1.92 2.63
29.58 1.56 1.46
25.83 1.16 1.10
22.95 1.17 1.13
19.54 0.83 0.88
17.02 0.72 0.38
16.35 0.60 0.18

Looks better to me. The separation between 95 and 100% is not big, 
but it is much better than before, and also the whole 90-100% range 
is better separated now. What do you think? Are these kinds of 
figures to be expected in the 90-100% range? Visually the new step 
wedge has better shadow separation, howver I still have a hard time 
distinguishing 95% and 100%. 

For the sake of completnesss I here include also the measurement of 
the 51-step wedge (with carbon curve applied), from which the ICC was 
made.

96.73 0.95 -0.41
94.84 0.98 0.23
92.62 1.07 1.05
91.22 1.26 1.61
89.68 1.39 2.24
87.99 1.50 2.87
86.86 1.68 3.35
85.26 1.73 3.94
84.32 1.86 4.24
82.84 1.94 4.59
80.87 2.03 5.11
79.76 2.11 5.41
78.60 2.20 5.64
77.70 2.18 5.83
76.57 2.32 6.09
74.96 2.40 6.36
73.52 2.46 6.61
71.99 2.58 6.85
70.50 2.63 6.98
68.56 2.56 7.13
67.52 2.72 7.23
66.01 2.72 7.20
64.51 2.81 7.47
63.43 2.85 7.39
62.31 2.87 7.35
60.96 2.84 7.40
59.80 2.89 7.38
58.79 2.90 7.35
57.39 2.93 7.35
56.13 2.94 7.27
54.02 2.90 7.12
52.55 2.86 6.97
50.89 2.85 6.73
49.32 2.73 6.39
47.54 2.62 6.12
46.04 2.59 5.78
44.44 2.51 5.45
42.99 2.44 5.22
41.14 2.32 4.53
39.38 2.30 3.92
37.70 2.27 3.52
36.05 2.11 3.05
33.98 1.92 2.52
31.49 1.78 1.93
29.19 1.55 1.43
27.40 1.50 1.24
23.83 1.28 1.21
20.88 1.16 0.92
18.07 0.85 0.66
16.88 0.63 0.42
16.48 0.53 0.26

Best regards

Didzis

 



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