Digital BW, The Print

Nick,

you don't mention the printer or OS you use, so the following may be 
somewhat generic troubleshooting advice :

-First you want to isolate issues that are built into the 2 drivers you are
comparing vs the profiles/curves you use with them.

- Then you may explore the profile further (though you seem to have done
a lot already). 

An efficient way to go about it is to make a half-inch square file of 100% black.
You can quickly print this on a sheet and keep repositioning it as you go. 
Keep notes to make sure you know what settings produced what print.

-  To find out if OPM produces less black than the Epson driver, you may print
through both drivers using only black ink. Using the profile you have for EEM in IJC,
turn off the other inks, then go up or down the limits while leaving the shape
of the black-ink curve as it originally was in the profile. Make several prints and
read them to see if the limits had any effect. Verify that the black ink curve is in
fact all the way up to the top right corner of the graph.
Likewise, turn the Epson driver to black only, leaving other settings 
(where possible) as you used them. Compare this to a similar print with the
Epson driver set to color and the black patch going through Paul's RGB
workflow - etc etc

You can further explore this with a 26step grayscale file (such as the one 
that I believe ships with IJC) and using a profile that has a straight diagonal 
"curve" for the black ink only (and a limit of 26), read the patches and determine 
which is darkest. This is the same as the built in Test Patches, but without the 
black squares meant to offer a visual way to determine the darkest patch. 
This way you can take actual readings and compare. You can also try the 
same exercise but with the black ink having an actual curve as it would 
in the final profile. You won't get a full scale to print, but you'll see
exactly what the black ink does in the profile.  Is the 100% patch still the same ?.... 

You pretty much get the idea of what I'm suggesting here: Try to isolate the
variables using a test file, not a real photo, and taking each component by itself.

It's possible that you'll find that the Epson driver produces a better black under
certain circumstances and there is nothing you can do with profiling. Or you may
find that OPM in fact could produce a black equal to or better than the Epson
driver if only the profile was tweaked. This may vary from printer to printer.

As has been suggested in this thread, a classic reason for loosing black density is 
too much liquid hitting the paper. This typically happens if too much of the dark 
gray (usually "cyan" position) or other inks print alongside the black. The same
can happen if the black level is too high.  

Not uncommon is the possibility that there is a difference between the dmax
you can achieve with a straight diagonal curve vs the one that really prints when
you apply the typical steep curve of the black ink. In that case you have to cheat
the limit that was determined by Test Patches (or the diagonal ink "curve"), 
but only enough to produce a "readable" improvement in density. You go any further 
and you start loosing density again because you flood the paper.

Antonis

 



--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Nick Nugent 
<nick_h_nugent@y...> wrote:
...

> It's not the the IJC/OPM image is flat, it's very nicely rendered. Smooth gradients with 
good details in both shadow and highlights. But measurements of darkest patches show 
the one printed using Paul's curve has the expected high DMax of 1.67 or somewhere 
about there. The one rendered by OPM yields about 1.59. This is enough to show the first 
one has significantly more punch when they are placed side by side.
>  
> Can someone explain?