Offset presses tend to run in two primary sizes, either 28” or 29” for half-sheet sizes, or 40” or 41” for full sheet sizes. The thing to remember is that most presses have a maximum image area corresponding to the press sheet, and the margin is anywhere from ⅛” to ½”, depending on the sheet size and the printer’s own preference. Solid colors are better run on a 40” press, since the rollers are bigger and the ink distribution is better. The thing to remember when designing for press is what the flat size of your piece is, and how it may run through the press. Don’t hesitate to call your printer and ask that question, because your design could succeed or fail if you design it in a way that won’t print well. For example, if you have a flat piece that’s 28.5” wide, and has bleeds, it can’t run on a 29” sheet, so it’ll run on a 40” sheet, and printers have a higher hourly rate for 40” presses. Also keep in mind that PMS colors are manufactured with specific colors as the "base", such as reflex blue, transparent white, or rhodamine red. The issues with these colors is that they do not reproduce well in the CMYK model, and you may have slight to great difficulty in having those colors come out correctly unless you pay for the extra cost of running them as PMS colors. Pantone has excellent tools for seeing how a spot color will reproduce in CMYK, which can impact whether you run the color as 4-color process or as a PMS.
Digital presses are excellent for short runs, for mailers, for anything that has multiple continuous tone images, or just copy. Photographs reproduce very well on digital presses, which has led to explosions in the photo book and self-publishing industries. Digital presses come in limited sheets sizes, though, and also have thickness minimums and maximums that don’t apply to offset presses. For example, most digital presses can manage either a max sheet size of 13 x 19” or 14 x 20”, and a few presses can do 14 x 26”. The HP Indigo has a model that can handle a 29” sheet size, and soon Kodak and Xerox will have 36” capabilities. The non-image margin is small on these—only about ⅛”—but most digital press operators would prefer a minimum of ¼”. They also cannot handle a great range of thickness, with 20 lb. bond pretty much the minimum, and 14 pt. board the max. The drawback to digital presses is the way the image is transferred to the sheet, which is not done by ink rollers but by transferring toner to the sheet where it’s fused by extreme heat. HP Indigo uses a liquid toner, which allows for a better image transfer, but also is more costly. Subsequently, cracking along folds can be an issue, and solids are particularly challenging and can be susceptible to streaking. Don’t let the digital press impact how you design, but do keep it in mind when you design. Digital presses cannot run PMS colors, but can have excellent results in reproducing the spectrum of PMS colors. The key there is to set up your file as the PMS color—do not convert it to CMYK. The RIP on the digital press will render the color much more accurately than if you save it out as CMYK.
Large format printing is imaged in three ways: high-quality inkjet, like Epson digital printers; UV inks like the VUTEk; or dye-sublimation. All of these processes allow for vivid reproduction of continuous tone images, but the main thing to remember when designing is to keep the copy simple, have large, readable fonts, and no heavily contrasting colors.
Knowledge of the press or imaging device can be very beneficial in ensuring that your design will print or image successfully. It never hurts to be in contact with the printer so that you can determine the best design possible for your client.
Next month, in the last installment, we will discuss paper and how it can impact your design, how to work with your printer on paper selection, and getting paper dummies made.
by John Prothero