Tips for Preparing a Book for Print-on-Demand Printing
The digital press that a printer uses to produce Print-on-Demand books is fundamentally different from an offset printer. Print-on-Demand presses use electrostatic imaging technology and wet or dry toners rather than ink from a printing plate. For this reason some adjustments and accommodations must be made in the creation of the digital file to avoid unexpected results. The following tips will help produce a book which conforms to expectations.
Talk to your printer. Find out what file types the printer accepts. Most will accept Quark and InDesign files. Some will take PostScript files with no trapping. Be sure to include all fonts and graphics. Many will accept PDF files; however, often the files must be in the PDF/X-1a:2001 setting. Discuss this with your printer. Templates for the interior layout and the cover should be downloaded from your printer. They usually provide templates which are based on the number of pages, your selection of paper and binding all of which govern where the margins and bleed space occur.
Picking the binding. Toner is not absorbed into paper and the toner is prone to cracking when folded. To minimize the cracking choose a laminated cover (the lamination will hold the toner in place) and a perfect-bound spine. If you use saddle stitching with toner, you will get cracks in any toner near the spine. Keep illustrations on one page rather than running them through the gutter space. Create the look of a continuous illustration by using two separate illustrations aligned to the gutter margin. Unless a reader breaks the spine, it is unlikely the break in the illustrations will be highly noticeable.
Selecting the paper. Digital presses can not run all the papers used by ‘offset’ presses. To get the best results choose a smooth white paper. It is best to avoid colored papers. Images will reproduce more accurately on a white paper. Some ivory papers may also produce satisfactory results. Textured and rough, recycled papers do not work well because the toner does not stick to them evenly. Matte- and gloss-finished papers give very different results. Ask your printer for advice.
Choosing the right software. Choose software designed to handle images for the layout (i.e. Quark, InDesign, Photoshop, Illustrator, etc). These programs are intended to support digital presses as opposed to word processing or slide production software (i.e. Word, PowerPoint) which are intended to produce overheads and slides. Word processing and slide production programs work best in the RGB color space. Conversion to CMYK colors is usually muddy and flat or the program crashes. Additionally, these programs have file size limits which are sorely pressed by the intensive use of graphics.
Artwork. Usually the biggest variances from the expected design occur in the artwork. This is largely due to the difference between what is displayed on the screen and what is subsequently printed on the page. Digital presses print in CMYK colors rather the RGB colors which are displayed on a computer monitor. Interestingly each program designed to handle graphics uses a different ‘engine’ to convert RGB colors to CMYK colors. Extra care must be taken to produce a satisfactory result.
Color in general. The monitor is capable of showing many colors which can not be duplicated precisely by ink or toner on a page. The computer will attempt to convert the RGB color into a CMYK color but it is rarely completely accurate. Expect a shift in color. The amount of shift depends on the printing equipment being used and the software program used to manipulate the artwork. The greatest amount of shift occurs when using computer colors in an image editing program. Scanning an original work of art produces the best results. The only computer color which is accurate is pure white. The other factor which helps create an unsatisfactory result when using computer-applied colors is the flatness. Flat color results in banding as explained next.
Large blocks of color. Toner-based devices do not print large blocks of solid color well. Due to variations in the strength of the electrostatic charge, they tend to leave streaks or bands of uneven color. To mitigate this problem add ‘noise’ to flat areas of color. Use image editing software to add texture or variation to the area. Another approach is to scan cloth or paper at 300 dots per inch (dpi) of the color desired. The cloth or paper adds texture and variation to the color block which reproduces well. If there is a large area of black, work with the printer. Most digital press operators suggest a ‘rich’ black which is a mixture of cyan, magenta, yellow, and black. The recommendation will vary depending on the equipment used, but it will involve all four colors instead of the addition of just cyan which is commonly used with offset devices.
Skip metallic looks. Toner-based presses do not produce metallic looks well at all. It is best to avoid them.
Avoid gradations. Digital presses print dots rather than continuous images. Normally the resolution is between 400 to 600 dots per square inch. In order for gradations to look acceptable with a digital press they need to be confined to relatively little shift from dark to light and benefit from the addition of ‘noise’ to smooth the edges. Shifts from very dark to very light usually result in banding.
Proof the work. The images of the book on a computer screen and the output of an inkjet printer are both capable of more subtlety than a digital press. Both are showing the image with more dots per inch than the digital press will produce. Additionally the monitor is showing the colors in RGB rather than CMYK. It makes sense to get a print out of the work (a proof run) or at least a print out of the colors in the work to ensure you get your desired colors in your final product.
Photographs. Digital presses reproduce photographs well. Photographs can be entered in the tiff format or scanned at 300 dpi on a good quality scanner. Space-saving file formats (i.e. jpeg and gif) do not reproduce as well. Use only photographs taken with high resolution. Grainy, sepia, crumpled, and stained photographs will reproduce poorly.
Now you know the strengths and weaknesses of digital presses and understand how to coax the best possible performance from them to produce a quality book.