"After two cuts one just sets the guillotine to the width and height of the job - not really aiming for the crop mark (or one hopes the cut lands on it at least!). "
This may be true in most cases, but there are jobs for which an even border all the way around is more important than an exact size. These should of course coincide in theory, but will not always do so in practice due to paper stretch for whatever reason. At that point in production, it will be too late to adjust the water setting.
You're right. But, depending of each guillotine operator, there are two methods to fix this issue:
1- the easy and quick way (as you explain): make the 2 first cuts at the crop marks, and adjust the regularity of the border around by correcting the size.
2- the long way: make the 2 first cuts at the crop marks, the two final cuts at the exact size, and adjust the regularity of the border around by correcting the two first cuts... this method is longer, but has the advantage to keep the exact size.
michaelejahn said:
There is never really any 'standard' answer to such a question, as this entirely depends on the project, how the design might be paginated or imposed.
Yes, right.
As said previously, the marks offset has to match with the bleeds!
... and the bleeds are essential and needed:
• for cutting to allow small corrections of size and to be sure that no white paper is left on the edge of a coloured area or of a photo
• AND for binding to allow variations in the folding and the collating.
Cutting is generaly quite accurate, but binding introduce sometimes "great" variations... so:
• jobs using only ONE sheet of paper, like a simple flat leaflet, or a poster (without any fold), or a "4-pages" (with only one fold) or a 2-folds leaflet, nedding only 4 cuts of a flat paper sheet without any binding are easy jobs that can be cut by a normally competent operator with a less than 1 mm of variation... so for that kind of job a 2 mm bleed and 2 mm marks offset are greatly enough.
(2mm = 5/64" or 0,0787" or 5,66 pt. The defaut setting of offset in XPress is 6 pt)
• for jobs using more than one sheet, needing first to fold some sheets with 2 or 3 or 4 folds, second to collate and bind all the signatures together, and finally to cut 3 sides, there are generally more variations due to the relative imprecision of folding... so, these jobs need more bleed and more offset: the minimum is then 1/8" (about 3 mm) up to 1/5" (5 mm).
The short answer would be: if you are not sure of the needs of the printer, the safety is to have 5 mm bleed and 5 mm offset (1/5") to match with all situations.
But using:
- 1/8" (3 mm) for "one-sheet" jobs
and
- 1/5" (5 mm) for books and booklets, saddle-stitch or perfect-bound
is a better solution.
I have always been dumbfounded as to why 0.0833" is the default setting in many applications.
Before PDF workflow, the default settinf had no real importance, as the marks offset was the printer's job and was set by the printer himself during the film burning process from native files, and the printers knows the good value that he needs depending of the job...
... with PDF, some parts of the job previously done by the printer have now to be done by the designer, who are not fully aware of all the technical needs of printing...
... but obviously nobody by Adobe and Quark had the idea that this new situation could need a new default offset setting.
(ALL the PDF that I receive and that are made by professionnal designer have the 3 or 5 mm bleed, because the need of bleeds are fully "accepted" by designers: all good designers know that bleeds are essential for printers...
... but many of them do not exactly understand/know the exact use of bleeds, and for these reason they don't see the relationship between the bleeds and the mark offset... and ALL PDF that I receive have the 6 pt defaut mark offset!!!)
