[cups.general] Postscript Printing Problem

[Ian Brace]

Hi,

In my CUPS setup I have two HP printers configured.  The HP5 is a B&W
laser and the HP4100 is a colour laser.  They are both spooled off a
remote unix host, so the URI is

lpd://server/HP5  and
lpd://server/HP4100

HP5 works perfectly.  However, when I send a postscript file to the
HP4100 it prints out the raw postscript instead of a formatted page.

I have worked out that what is happening is that my postscript files are
being "processed" again by CUPS into ....postscript!  This "double
handling" causes the printer to then see the file as text.  The log file also 
shows the filter "pstops" being used.  If I use

lpr -o raw filename

then it prints perfectly because it goes straight to the printer, and
since it is already postscript the printer recognises it and prints it.

So, my question is WHY??  The B&W printer has no such problem, but was
setup/installed the same way.  How do I turn off filtering in the
printer setup for the colour machine?

Thanks,

Ian.