Dave Pawson wrote:
> For the non print house aware amongst us,
> Any chance of a very quick thumbnail of what goes on
> with this pre-flight idea please?
> I won't ask where the silly name came from :-)
> AFAIK the bottom line is to present the printer
> with n documents, each containing a single color,
> which are duly overprinted (which is why you need those line up marks).
"preflight" is a general term of art refering to any processing or
preparation need to make the files you deliver to the print house ready
for printing. Most print workflows are PDF based, although some are
still PostScript based.
Preflight actions can be many and varied, but include:
- Color conversion (e.g., from RGB to CMYK or process colors
- Adding registration and printers marks
- Normalizing rule weights
- Adding or adjusting page boxes (trim, etc.)
- Checking that fonts are correctly embedded or not embedded as the case
- Creating color separations (one copy of each page, rendered in black
and white, for one of the four CMYK colors)
See Web sites like PDFZone and PlanetPDF for more information about
PDF-based preflight workflows and tools.
Most preflight processing is necessitated by the use of various word
processing and desktop publishing tools that give wide latitude in the
details of how they produce PDFs. With a more controlled system like
XSL-FO, it should, in theory, be possible for an XSL-FO implementation
to produce PDFs that require no additional preflighting in order to be
printer ready. However, that is not the case today, at least with the FO
implementations I've worked with, and also varies depending on what your
print vendor's requirements are. For example, many print vendors prefer
to do color conversion and separations themselves, others do not.
W. Eliot Kimber