printing to Docutek issue ... rasters looking 300dpi (pixelly)

[Dov Isaacs]

Repeat after me ...

	"Write White is Never Quite Right!"

Most likely the problem is that the Docutech is not
properly adjusted. Many of the Xerox Docutech high speed
monochrome digital presses are direct descendents of
high speed analog copy machines. As such, unlike most
laser printers in which the "laser on" condition results
in toner being applied to the imager and then paper 
(technology known as "write black"), in this older 
technology, the "laser off" condition results in
toner being applied to the imager and then paper
(technology known as "write white"). The problem with
"write white" technology is that to avoid gray casts
on the output, the width of the laser beam is much wider
than the unit of resolution. For example, on a 600dpi
Docutech, the width of the laser is closer to 1/300" 
than 1/600". As such, single pixel lines and fine 
detail in halftones may effectively disappear. To
counteract this, Xerox does have some interesting
features within the Docutech to try to recognize
such situations and "fatten up" the lines or halftones.

In your situation, it is possible that the Docutech
is actually over compensating for thin lines and
especially fine detail in halftones. Have Xerox
service the Docutech!

________________________________

>	Sent: Wednesday, December 28, 2005 1:17 PM
>	To: framers at lists.frameusers.com
>	Subject: printing to Docutek issue ... rasters looking 300dpi
(pixelly)
>
>	Hi,
>	
>	 Printing to a Xerox Docutek from a PDF (version 1.4
compatibility created created in Acrobat 7) from FrameMaker 7, the
screen captures look low-res, 300-dpi-ish (a bit pixelly).
>	
>	 The Job options are set as follows:
>	
>	 Resolution on the main tab = 600dots per inch
>	
>	 On the Images tab:
>	 For Color and Grayscale Images Downsampling is turned Off and
Compression is set to ZIP.
>	 For Monochrome Images (which I assume does not apply to screen
captures), Downsampling is set to 1200 ppi for images above 1800 and
Compression is CCITT Group 4, with Anti-alias to gray turned Off.
>	
>	 The images in the FM chapters are generally set to a resolution
to fit the text column, between 120 and 216 dpi with very few, if any,
above that.
>	
>	 These PDFs print fine off a variety of office laser printers
(Kyocera and HP) and ink jets (mixed brands), etc. The Docutek in
question prints text and line art fine and has a printing resolution of
600dpi.
>	
>	 Anyone offer any advice?
>	
>	 Thanks,
>	
>	 Sean