Crop Marks – is this how they work?

[Guy Burns]

I haven't had to use crop marks before – my books have been printed on sheets the same size as the InDesign page. Now however, I am about to print a small book, 4-Up, on sheets larger than the page size, so I will need to add crop marks. I want to run my understanding of how to place crop marks on the page and how they will be used by the guillotine man, past some of the experts on this forum.

And before anyone says: "Crop marks are the printer's job. Just let him do it", or somesuch comment – in this case it's not the printer's job, it's mine. I've chosen to do everything: the writing, the layout, purchase of the paper (910 x 650 sheets), the cutting of the paper, the imposition, the printing, arranging the cutting of the sheets, and then the binding. So, I need to know about crop marks. This is what I have discovered, or guessed (please correct me if I'm wrong):

Assume a page size in InDesign of 100 x 200 mm. When you export to PDF and tick Crop Marks and set Offset to a certain dimension, two things happen:

1. The page size is increased to (100 + 2 (Offset + 5.3)) in width, and (200 + 2 (Offset + 5.3)) in height. In the case of an offset of 5 mm, the page dimensions of the PDF become 120.6 x 220.6 mm.
2. Crop marks of 5.3mm in length (5/12"), are placed at the four corners of the new page pointing inwards to the original page size. Thus, in this case, there is a gap of 5mm, the chosen offset, between the end of the crop marks and the original page. This offset allows for movement of the sheets during printing, so that when the crops are made the crop marks won't appear on any of the pages. i.e. the offset is greater than the expected sheet movement.
3. The guillotine man, when he comes to cut the sheets, lines up the narrow beam of light from the guillotine with one of the crop marks – and cuts that edge. Now there are only two crop marks left because two have been cut off in this first cut.
4. The guillotine man then rotates the sheets 90º and cuts again. Now there is only one crop mark left.
5. The sheets are again rotated, the beam of light lined up with the remaining crop mark, and the third cut is made. There are no more crop marks left.
6. For the final cut, the sheets are rotated 90º, but as there are no crop marks left, the appropriate dimension has to be entered into the guillotine (or marked out on the top sheet), and the cut is made.

I have yet to confirm with my guillotine man that steps 3-6 describe how he will do it. That's simply how I imagine it would happen. And in the case of 4-Up, a couple of extra cuts will be needed in the centre, depending on how the imposed pages are positioned.

Is the above an accurate description of how crop marks are inserted and how they are used?

[Stix_Hart]

Good on you for doing the whole thing yourself!  But I can imagine if I was the printer doing it I might get a little bit frustrated so be patient with them!  I used to be a printer and you've got it pretty much right.  However in points 3-6 there are a few things* that an experienced guillotine operator can do to get it better.  Most guillotine operators though (in my experience) have their own method and don't like to change.

Personally if adding Crop marks in InDesign (I prefer to use an imposition program) I like to make them even numbers, e.g. 3mm offset and 7mm long crop marks, whoch give a PDF size that is bigger by 10mm on each side.

* to start to list them:

1. you don't just go by them beam of light.  You make a cut 3mm out and them measure it on each side of the sheet (most guillotines are perfectly straight).  Then you creep it in by say 2.7mm and you've got it much more accurate.
2. When you do that first cut you can do it precisely 5mm out, then you can still keep using the crop marks.

[Silkrooster]

That was always my understanding. which is why when I have to do any cutting, I create my own crop marks and invert the shapes, that will leave a line on the remaining side. In other words the marks are pointing inwards instead of outwards. Yeah I know its not proper, but it works for me. Another option is to create a border and assign it a dashed pattern. But I prefer the inverted crop marks. Just so I can feel a little bit professional, even though, well you get the idea.

[Jongware]

Take out your straight ruler and draw the final page size on the top sheet only. That's how we used to do it. (Not me personally, I was mortally afraid of that 300 lbs razor sharp piece a metal hanging above my hands.)

[Colin Flashman]

@OP:

So far as your observations about the guillotine, I generally agree with steps 1-6, but stress that guillotining flat sheets is something that I would do for letterheads, business cards... things that are a single page, NOT a book.

Most guillotines normally have programs too so that all necessary measurements can be plotted in so that measure by sight is only used for the first test cuts. Guillotinists don't normally cut one stack, but dozens, if not hundreds using the same cuts - they will get their measurements right once, plot in the measurements, and then cut using the program.

Also, so far as I am concerned, cropmarks in InDesign aren't necessary as my imposing software (Creo Preps) puts my cropmarks on the artwork, as well as colour bars, fold marks, registration crosshairs, etc. Is the OP imposing this artwork in InDesign, or using something like Preps or Dynastrip?

I work for a printer in the prepress section and it is my job to prepare impositions for press not only for guillotining, but FOLDING as well, and that appears to have been overlooked. What generally happens is a book that size (which is an unusual finished size) would be imposed onto the 910x650mm IPS sheet in such a pattern that once printed, would be passed through a folding machine which would perform conventional folds so that the pages would be in sections. These sections are then gathered together on a binding line, have a cover attached to it, and get cut with a device called a three-knife (two blocks - one with one knife to remove the foredge, and another block with two knives to cut the head and tail from the book).

Or is the OP going to impose each sheet with 24 pages to view (what I've calculated will fit on the sheet, assuming there is no bleed) and impose so that the pages get cut out as single pages and then hand-collated? How many pages are in the book? How many copies of the book are required? Why is the OP handling this and not the printer? I'm sure there are good answers to all of these questions but they are not in the opening post.

[Guy Burns]

Thanks for the responses.

Stix: Personally if adding Crop marks in InDesign (I prefer to use an imposition program) I like to make them even numbers, e.g. 3mm offset and 7mm long crop marks, whoch give a PDF size that is bigger by 10mm on each side.

• Yes, it would make it easier if numbers were whole integers. But how do you tell InDesign to make a certain-length crop mark? I assumed it was fixed at 30 point (5/24" = 5.292 mm).

cdflash: I'm sure there are good answers to all of these questions but they are not in the opening post.

• I tried to keep my question as simple as possible, hence I didn't elaborate. But to answer some of your queries…
• Or is the OP going to impose each sheet with 24 pages to view?… I am imposing using only InDesign using a method I developed. It's a very flexible method and works beautifully for 2-Up and 4-Up. Some of the imposition software I trialled several years ago was highly sus and not capable, for example, of generating variable-length signatures. I suppose the up-market programs would be okay, but I can't justify spending thousands on a program I might only use a few times.
• Out of interest: can the software you suggested, Creo Preps, impose with these signature lengths: 6,6,4,4,4,8 (numbers of sheets per signature; total 128 pages)?
• How many pages are in the book? How many copies of the book are required?… Size of Coracina is 148.5mm x 191 mm, 128 pages, 50 copies. The figures I gave for page size were examples only.
• … and impose so that the pages get cut out as single pages and then hand-collated?… Printed sheets are 4-Up on SRA3. I chose SRA3 late in the piece when the printer told me that the click-charge was the same no matter what the paper size. Prior to that I was intending to print on A4. Printing costs are now halved.
• Why is the OP handling this and not the printer?… I like a challenge, I like to be in control of the process, I like to learn, and I like to save money.

Tanksinker

Check out the images at the bottom of https://sites.google.com/site/tanksinker/Home/max-burns-tanksinker if you'd like to see how I make a book. Doing it all myself results in huge savings. Tanksinker cost me about $10,000 all up, only half of which I got back in sales. It's a hobby. I don't expect or want to profit from it. To print 50 copies of Tanksinker commercially, judging by what a local offset printer told me, would have cost $50k-100k for the plates alone (2 proofs, 400x4 plates each proof, $20-30/plate).

Coracina

I have been to see the guillotine man after reading all the posts above, and he confirmed that the crop marks I was using would be suitable (I just drew them on a piece of paper; I didn't show him the real thing). He did make a useful suggestion: he would trim the SRA3 sheet along the top and bottom of each book-spread (4 horizontal trims), but not trim to the left and right crop marks (vertical trims) because that would be done anyway when trimming the fore-edge after the book was sewn and glued.

A sample page of Coracina, with crop marks ready for printing, can be downloaded here: http://www.mediafire.com/?5eidx1c61o7jrjx

Printing of the first three copies is tomorrow morning, Tasmania time. If the crop marks on the sample, or any other aspect of the layout looks in any way sus or likely to cause problems, please let me know.

Oh, and I should add that Coracina is my partner's book. Way too girly for me. I'm just the technical consultant, shall I say.

[Peter Spier]

Guy Burns wrote:

Thanks for the responses.

Stix: Personally if adding Crop marks in InDesign (I prefer to use an imposition program) I like to make them even numbers, e.g. 3mm offset and 7mm long crop marks, whoch give a PDF size that is bigger by 10mm on each side.

• Yes, it would make it easier if numbers were whole integers. But how do you tell InDesign to make a certain-length crop mark? I assumed it was fixed at 30 point (5/24" = 5.292 mm).

Well, it's not easy to change the length of the mark, but you can still change the offset to make the total outset whatever you want.  My printer uses a custom .joboptions file that adds enough outset to leave exacly half an inch (we're in the US) all around. That's their margin of choice on press. They have another set for the digital copier that leaves only 3/8" so they can print letter-size two-up with bleed on 12 x 18 and still see the outside marks.

[Colin Flashman]

OK, I see what is going on now. What I would term short run digital printing.

The OP may be interested to know that my employer does this kind of work, and won a major national award and local state award at the PICAs (Printing Industry Craftsmanship Awards) for a similar project. A link can be found here: http://tinyurl.com/74hrm4b

There are definitely huge savings printing a short-run book digitally as compared to with offset printing which requires plates to be made. In terms of digital printing, the competition is fierce and there is plenty of digital printers about. For a book like the OP has, I would choose one that has a reputation for quality rather than quantity. Not all printers concentrate on specialised case-bound bindery though, but the third party that we use has consistently performed excellent work. The competition for this kind of bindery though is few and far between, and probably the most costly item.

However, I am still of the opinion that the imposition should be handled by the printer. This lets designers concentrate on the creative side rather than the mechanical, and also puts the onus back onto the printer in case the imposition is incorrect or has complications. On books like the one the OP has, we would typically print the book as single leaves 4-up on SRA3, print the text as complete sets, and then hand that onto a third party to complete the bindery. Single pages do not allow for section sewing, but DO allow for a similar technique called stab sewing.

In terms of the Preps question, for a job like this it would be overkill.

If the OP insists on preparing the imposition himself, I would  get the printer to draw  an imposition diagram so that you can see how HE wants the imposition prepared. It should contain instructions such as head directions, gutter measurements, and marks he needs such as crop marks, fold marks and collation marks.