[Scribus] Re: Crop mark
Sun Sep 18 22:07:18 CEST 2005
On Sun, 2005-09-18 at 21:56 +0200, Christoph Sch?fer wrote:
> Hi Asif,
> > All of it flew past over my head! I don't understand anything about
> > crop marks. Would you elaborate more on it please? Further, what is
> > "Bleeding" stuff? Just out of learning and curiosity.
> all these features are necessary for professional printing, which is
> quite different from printing on your inkjet.
> In most professional printing processes, content is printed on larger
> sheet than the page with the content. To get the best results and to get
> around some inaccuracies of printing machines, lots of different marks
> need to be printed on these sheet, which have nothing to with content:
> 1) Crop marks: Since the sheets are larger than the intended page size,
> they need to be cut (cropped) after printing. Crop marks tell the
> printer exactly where to cut.
> 2) Centre marks/fold marks: In most cases, the printed sheets will be
> folded, and the printer needs to know exactly where.
> 3) Registration marks: These marks allow the printer to control if the
> content has been placed accurately on both sides of a sheet.
> Other things might also need to be printed, such as a colour scale, a
> densitometer scale or backup registration. All these things are
> neccessary for the highest degree of control in the printing process.
Many preflight tools and/or RIPs generate these automatically now, so
you should generally check what your printer requires you to add. It's
increasingly common to simply be required to provide a PDF with a
(usually 10mm) border for bleed.
The printer my work uses rejects jobs with marks added. Their tools do
it automatically, adding marks that their press and post-printing gear
will recognise and handle. They use this for adjusting ink flow during
printing, automatically trimming pages, monitoring registration during
printing, and more. It's all rather impressive, actually - and
customer-added marks just get in the way.
> As for bleed, this has also to do with little inaccuracies of printing
> machines. Imagine you want to have a photo on a page that is to end
> exactly at the page margin. For that reason, you add additional space
> (mostly defined by the printer) and drag the photo a bit over the "real"
> page margin. That way, you can be sure that the photo really ends at the
> page margin and there is no white space left, due to inaccuracies of
> printing machines. Most professional graphics and layout programmes have
> a "bleed" function that lets you enter the values required by the
> printer. Scribus doesn't have this feature yet, so you need to follow
> Louis' advice on the Wiki.
This also helps ensure that there's no tapering off of the colour at the
edges, printing inaccuracy aside. Here's my (probably rather limited)
With many printing technologies, ink "bleeds" into a page - each dot
expands from where it's printed. With newspaper litho printing this is
as much as a 30% expansion, so it's pretty significant. If the printer
was to stop exactly at the edge of your page, you might get a frayed
looking edge from where dots didn't quite make it onto the page, but
they would have expanded well onto it. By printing a small amount
outside the borders where the page will be cut, this problem is
eliminated. My understanding is that it only matters for edge-to-edge
printing (flyers, gloss magazines, brochures, etc).
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