Printing question (was Re: [netatalk-admins] PPD files on server)

[PayPC System Mail Subscriber]

Thanks Jeremy, for the excellent summary of how to setup LPR printers under 
LaserWriter 8.5.1-8.6.1

I myself have used that technique, but you spared me the hassle of writing 
how to do it for my other users! :)

I have a question the printer gods on the list can probably answer (I'm sorry 
it's not netatalk-specific, but I have no other people I can ask within easy 
reach).

It's such an annoying little problem too, I'm sure someone has a ready answer 
that's super-obvious to the DTP guys.

Environment:

OS 8.5.1, ColorSync 2.5.1, Viewsonic G810, configured for 9300 K white point, 
1.8 gamma, LaserWriter 8.6, with HP's Laserjet 8.6 PPDs.  Printer is an HP 
Laserjet 4M [PostScript Rev 2011.110, 6MB RAM] 600 dpi.

Application:

Adobe Photoshop 5.0.2, properly informed of my ColorSync profile.

Here's what I do:

I take an image [it's just like a driver's licence photo -- medium light 
background, head-shot, brightness and contrast corrected on my Viewsonic 810 
display.  It's 100 dpi and is Grayscale.

Problem:

When I print it using "default printer screens" as-is, I get a "correct" 
looking printout, but it's "grainy" like a cheap newsletter picture.... I 
suspect it's because it's using 83 lpi screen or something worse.

Now, the real problem comes when I try to be "clever" and do the bitmap 
conversion myself.   I've tried probably 80 different ways....  

from Diffusion Dithering [which seems to do a correct job of converting the 
levels to perceptual "levels" look at as a whole] but alas it prints out 
HORRIBLY dark.  And the "medium light" background [even though the diffusion 
dither is also "medium light" in overall tone, gets printed out as SOLID 
BLACK!

OK, so then I try doing my own screens, however, aside from the 83 lpi 
setting, I can't find one that doesn't leave "tartan plaid" artifacts in the 
image.  I'm using diamond shaped, 45 degree, and yes, I've done the Sqrt(2) 
conversion factor, etc....  Theoretically, 141 lpi should be the optimal lpi 
for my image, no?  (100 dpi input, 600 dpi resulting bitmap).  

Does anyone have any advice for screen angles/lpi or a program to calculate 
these quickly and optimally for: 1) image dpi, 2) target device dpi, etc.  I 
am quite sure this is a blacker "art" than SCSI, but I imagine the print guys 
have figured out the basics.

When I MASSIVELY adjust the "Levels" of the image prior to using Diffusion 
Dithering, (making the image almost totally washed out white), the printout 
just STARTS to get close to be overall recognisable, but it's still quite 
poor in quality.

What am I missing here?  Is my PPD bad?   In all of my tests, I have "Smooth 
Graphics OFF" and HP's Resolution Enhancing Technology OFF.  I also have 
Black & White Colour Matching (as opposed to Colour/Grayscale).

I am almost tempted to write a PCL raster test program to see if it's 
something the printer engine is doing [unlikely] or some weird-ass 
interaction with PostScript and/or the LaserWriter driver [more likely].

Thanks for any help you guys can share,
=Rob=