Digital BW, The Print

Ok here are the results from the tests mentioned below ­ L measurements
first then density:

     
 Step Image L QTR L Epson L BO 2.2 L BO 1.8 L  QTR D    Epson D      BO 2.2
D    BO 1.8 D
 0      100     97.09   97        97.04     96.98         0.033
0.034       0.034       0.034
 5       95      92.02   92.8     93.31     94.38         0.093
0.083       0.077       0.065
 10     90      87.08   87.87    88.72    91.04         0.154         0.144
0.133        0.105 
 15     85      82.46   83.22    84.69    87.36         0.214         0.204
0.184        0.15  
 20     80      77.76   78.72    80.47    84.11         0.277         0.264
0.24          0.192
 25     75      73.35   74.46    76.77    80.93         0.34           0.324
0.291        0.234 
 30     70      68.67   69.65    72.49    77.57         0.41           0.395
0.353        0.28  
 35     65      64.1     65.67    69.27    73.76         0.482         0.457
0.401        0.334 
 40     60      59.7     61.86    65.19    70.52         0.556         0.519
0.465        0.382 
 45     55      55.82   57.5      61.97    66.97         0.625         0.594
0.518        0.437 
 50     50      51.98   53.05    58.03    62.87         0.696         0.676
0.585        0.503 
 55     45      47.68   48.43    54.89    59.53         0.781         0.766
0.642        0.559 
 60     40      43.54   44.3      51.33    55.5           0.869
0.852       0.709       0.63
 65     35      39.66   39.76    47.99    51.42         0.957         0.954
0.775       0.707  
 70     30      36.76   35.93    44.91    48.45         1.026         1.047
0.84         0.766 
 75     25      33.96   32.26    41.69    43.97         1.097         1.143
0.91         0.86  
 80     20      31.12   29.06    38.24    40.38         1.174         1.232
0.991        0.94  
 85     15      28.72   25.18    35.06    36.37         1.242         1.35
1.069       1.036  
 90     10      26.41   22.99    30.6      32.17         1.311         1.42
1.188       1.145  
 95      5       23.69   19.04    22.21    23.71         1.397         1.559
1.447       1.397  
 100    0       18.32   18.1      16.86    16.93         1.587         1.595
1.644       1.64

(hopefully the formatting will stay there)

Some observations:

QTR and the Epson colour profile are very close but with some separation,
particularly we approach the darkest steps.

The Epson colour profile may be affected by the fact that I formulated the
profile for post spraying of Lascaux fixitive which I did not apply in this
case.

BO with gamma 1.8 is way off ­ as expected since we have used a Same as
Source workflow and chose a gamma quite different from the workspace.  BO
users would be advised to use gamma 2.2 rather than 1.8 particularly if
prepping their grey scale images in Adobe RGB, Lab QTR Grey Lab or Grey
Gamma 2.2.

BO 2.2 is better but still quite off and will generally print ³light² - note
the mid grey value of 58 vs a file value of 50.

QTR prints mid grey the best ­ QTR is actually less ³flat² than the others.

Remember that linearity for the Epson and QTR prints will be overridden
somewhat by the perceptual rendering.



> From: Steve Kale <stevekale@...>

> 
> David et al
> 
> Last night I printed a Lab step wedge four times on EEM on my 2100
> (workspace QTR Grey Lab).  Once with the Epson driver using an Eye-One made
> colour profile for my printer and perceptual intent etc, using Black Only
> with gamma 1.8, then Black Only with gamma 2.2, and finally using the canned
> QTR profiles 50:50 warm/cool (which would have had linearised Lab values and
> hence a rough gamma of 2.2) using the perceptual intent workflow.  I will
> read the results with my Eye-One later today when I get the chance and post
> them.  Visually, though, the QTR and the Epson colour print look very
> similar in density distribution (I won't comment on hue as we know the BO
> will be off).  The BO step wedges, I suspect, are going to show a real
> bunching of density up around 90-100.
> 
> I don't have the Epson inks installed but rather MIS' UC equivalents with
> Eboni in the K position.  This should provide, though, a more accurate
> comparison of the various workflows.  In no case did I apply a "contrast
> curve" to the step wedge ie it is a straight out of the box print.
> 
> Steve
> 



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