Imposition is essentially the placement of more than one image on your camera ready artwork to take best advantage of the sheet size or press size your job is going on. For example, if you were printing a 5.5" x 8.5" flyer, you would likely output the art with 2 flyers side by side on an 8.5"x11" so that you could print two flyers at a time on an 8.5" x 11" sheet. With more complicated jobs, you will also have to ensure that appropriate crop marks and registration marks are included with the imposition. See Creating Output Ready/Camera Ready Art for more information on registration and crop marks.
Typically, designers and desktop publishers supply artwork for print in one of two ways: either "one-up" or "imposed." One-up is great in situations when you don't know how your job will be imposed for the press. In this case the printer takes the image and imposes it as appropriate. Imposing your artwork is great if you know exactly how the job needs to be imposed. In this case, the printer doesn't have to modify your supplied file and you will not have to worry about extra charges for imposition.
There are a few different criteria for deciding whether you should impose your jobs before sending them to the printer. Generally, if you're confident you can do it properly by yourself, go for it! If your printer isn't sure exactly how they are going to impose a job or if it is complicated imposition, you'll likely be better to leave the imposition to them. This is particularly true in situations that involve multipage documents such as books or manuals. In these cases, the imposition may be quite complicated as the printer will carefully plan how best to place the pages to make efficient use of the sheet AND to ensure that the pages are in order after the binding process.
We'll look at how some typical jobs are imposed to illustrate some of the concepts you need to know.
Business Cards are typically imposed either 4 -up or 10-up. The 10-up imposition is usually done with cards that are printed on 8.5"x11" sheets and do not require super-tight registration (lining up of multiple colours). 4-up imposition is often used with cards where excellent registration is required as it reduces the total area that has to be "in-register" and makes it easier to ensure perfect registration. Also, for custom stocks, the size of sheet (5"x8") that is often used is a very effective cut from larger sheets of stock.
Let's look at the earlier example of a 2-up 5.5"x8.5" flyer being printed on an 8.5" x 11" sheet. This requires fairly straightforward registration unless the flyer has "bleeds." If the flyer had a photo in the background that bled off all four sides, the image would need to extend past the 5.5"x8.5" edges to ensure that there would be no risk of having unprinted white edges left on the edge of the flyer when the job was cut. This would mean that two flyers would no longer fit on the 8.5" x 11" sheet (particularly after the necessary crop marks were added). In this case, there would be a couple of choices. You could either print the flyer 1-up on the 8.5"x11" or use a slightly larger sheet and still print two up, with a "gutter" between the two imposed flyers to leave room for the bleed and the crop marks. In this situation it's definitely best to consult with your printer before performing the imposition.
Longer Publications - Newsletters, Books, Catalogues
For this example, let's use a 32 page newsletter with two 8.5"x11" pages printed on each 11"x17" sheet, folded and saddle stitched to a final size of 8.5"x11." If you were printing the newsletter on a press or copier that had a maximum size of 11"x17", the imposition would be quite straightforward. The signatures (the 11"x17" sheets) would have page 32 placed next to page 1, page 2 placed next to page 31, etc. By doing this, the pages would be in the proper sequence after the pages were collated, folded and bound. Software packages such as Adobe InDesign or Quark Express have built in features that will perform this imposition for you.
If you have a publication, however, that is going to be printed on a much larger press sheet (or on a web press), you not only have to worry about which pages are placed next to each other on the press sheet, you also have to worry about which signatures are place next to each other. This is further complicated by the fact that way the publication is bound may impact the way it needs to be imposed. In this case, you're better to have your printer perform the imposition. Printers specializing in this type of work will usually have special software to perform these complicated impositions.
While imposition is certainly not the most exciting area of desktop publishing and graphic design, its essential to have an understanding of it so that you can have jobs quoted properly (i.e. by specifying bleeds if they're going to be used in your job). Because imposition can get quite complicated, it's a good idea to consult with your printer on their imposition process before setting up a job.
We strive to be as accurate and current with our information as possible. Due to the infinite number of scenarios that occur in print & desktop publishing, we can not guarantee that the above information will be correct in all situations.