The following are instructions for preparing low resolution (7 micron minimum feature)
UPDATE MAY 2011: Direct write to 4" soda-lime chrome mask now available
for features down to 3-5 microns ($225 ea), or in a "best effort" mode 2-3 microns ($337). Typical corner radius 2 microns. No more than 3 defects >5 microns per square inch.
UPDATE (Oct 2010): Photoplot store is back, with production by www.fineline-imaging.com. You can use fineline directly or go through photoplot (Richard Sayer is at photoplot is helpful with questions and tips).
photoplot FAQs and minimum feature sizes (this link is useful but may eventually break; photoplot store is no longer in business).
Prepare file in LEDIT