Digital BW, The Print

Antonis,

I ran some density tests.  I used both my densitometer and my colorimeter to 
double check all readings.  Both sets of readings were within 1/100 of each 
other.

First, I wanted to see if the Epson 2200 driver ran the same under Mac and 
Windows.  I ran this test with your 26-step wedge and black-only ink.  
Readings were equal within 1/100th.  My results are linear, again within 
1/100th.

My Epson dmax is 1.66; yours was 1.72.   

But where we differ is in linearity since you dip into dark from 50% to 100%. 
 I rechecked my settings and they are the same as yours.

Second, I made readings of OPM black-only, 26-step wedge.  My dmax is 1.62; 
yours was 1.68.  Readings were pretty much linear (not perfectly linear) 
until patch #22.  I get big jumps from patch #22 through patch #26.  The big 
jumps are linear but about 3-4 times as big as the jumps from patch #1 
through patch #22.  

Up until patch #15, the linearity and readings were equal between the Epson 
driver and OPM.  Then they start to separate up to 100% black.  (If I 
remember correctly, this finding from 0 to 50% is consistent with your 
results.)

Our linearity results are exactly opposite.  My Epson driver is linear and 
OPM is not.  Your OPM driver is linear and Epson is not.  I have no idea what 
to make of any of this.  Do you have any thoughts?

Helene
   

> Helene,
> 
> glad to see you ran the test, so we can compare notes. Some of mine to 
> follow 
> yours:
> 
> 
> >1.  Using the OPM black-only profile, I still get banding in the 100% 
> patch.  
> >My thinking is that if it's ink starvation, a faulty black cartridge, or a 
> 
> >bad black head, I would be seeing banding throughout your 26-step patch.  
> Do 
> >you agree?
> 
> Yes, that seems logical.... The mystery, of course, is that I don't see 
> that 
> behaviour on _my_ 2200. So it remains worth exploring further....
> 
> 
> 
> >1.  You see a herringbone pattern in the Epson driver; I do not.
> 
> That may well be differences in head alignment (since presumably you are 
> using the exact same Epson driver settings). I should re-visit that 
> procedure 
> on my printer, perhaps.
> 
> 
> 
> 
> >
> >2.  My Epson driver has a nice long tonal scale, unlike yours which dips 
> into 
> >dark from 50-100.  Like yours, the dots are most apparent in the midtones.
> 
> 
> Hmm.... that makes no sense: we should be getting identical density results 
> for 
> identical driver settings. Do you mind double-checking that your page setup 
>  
> and other print settings in PS were the exact same as mine?
> As for the dots themselves, we are in agreement.
> 
> 
> >
> >3.  The OPM driver is more compressed.  From 0 to 44, I see white 
> striations 
> >in the top part of the scale.  I see these with my eye but cannot see them 
> 
> >under a loupe.
> 
> We see the same there. The highlight dots are too scattered up close to see 
> 
> the striations under a loupe. The "top" part of the scale, presumably means 
> the 
> continuous gray ramp that appears above the individual patches as they are 
> laid out horizontally. 
> 
> I don't know if these breaks or "striations" are a result of the particular 
> profile, 
> though. I didn't spend time exploring that further. I just made sure the 
> patches 
> came in at the proper densities. Tiny moves in the profile may make a big 
> difference here, don't  know....
> 
> 
> 
> 
> OPM's midtone dots 
> >are less apparent than Epson's.
> 
> We agree on that too.  Hence my conclusion that in a real bw print 
> situation, 
> it's the mid tone dot that matters most for partitioned gray inks.
> 
> 
> Interesting comparisons.... thanks for reporting back.
> 



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