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.
> 



[Non-text portions of this message have been removed]

The subtle black banding has returned in my 2200 after getting 
rid of it by changing black ink carts last week.  Now that the  
current black cart is getting emptier, it is banding in deep, deep 
shadows.  I don't know if it is a cart problem, an inkjet head 
problem or an OPM issue.  I am keeping track of Antonis' and 
Helene's research on this, but I don't see any answers yet.  
Please keep me in the loupe.

Frank

http://www.photoeye.com/frankward