Printing & Design Tips: October 2002, Issue #15

Proofing Halftone Patterns

A client of mine recently decided to go back to requesting bluelines instead of digital ink-jet proofs for checking her work. She had scanned a map (previously printed and therefore including a traditional halftone pattern), descreened it, then finally sharpened the photo. The image looked bad but acceptable on the color ink-jet proof and horrible on the final, printed piece. The moire pattern created by descreening, then sharpening, then rescreening the map caused the problem, but it was far less offensive in the ink-jet proof than in the printed piece. So in this case the ink-jet did not function as an adequate proof.

Why? What could my client have done to avoid this? First, understand that the ink-jet proof does not display a traditional, offset printing halftone pattern. An ink-jet proof is composed of tiny dots. This "dithering" process differs from traditional halftoning in the following way: Although tones are composed of patterns of miniscule dots of color, side by side, to create the appearance of all colors, the dots do not conform to an equal-spaced grid and do not vary in size based on the amount of color, in the manner of a traditional halftone.

So what? If you need to see a halftone pattern (to catch possible moire patterns, which are the result of one set of equally-spaced halftone dots conflicting with another set of halftone dots), you need to see a blueline as well as a color inkjet proof. Or, you can ask for a "velox" or "white-print." This process, like the blueline process, shows the traditional, printer's halftone screen pattern. Of course, since a four-color image is just four superimposed halftones set with their dot patterns at specific angles to one another to minimize moire patterns, you might ask for either a matchprint, a cromalin, or a Kodak Approval when proofing a four-color project. The last option is one of the few digital proofs that will actually show the dot patterns (called rosettes in four-color work).

I also reassured my client that a blueline should cost no more than a color ink-jet proof if the job is not a direct-to-plate job. In both cases film must be produced. However, whereas an author’s alteration to a color ink-jet will cost very little (since no film has been run yet), authors’ alterations after a blueline or color laminate proof (matchprint, etc.) has been run will be very expensive. In the former case, proofing and correction are done prior to film output, but in the latter case film is run to make the proof. Therefore, any corrections require running all film a second time. This can be very expensive in a multi-color job.


Unlike offset printing, folding--an aspect of production under the general term finishing--is one of the least precise of the machine processes in the graphic arts. Each step is one of diminished accuracy. If the first fold is slightly off, the second will be worse. Inaccuracy cannot be remedied in the following folds. Industry tolerance is 1/16" either way or 1/8" total. This can wreak havoc with crossovers (especially if they involve type crossing the gutter). This is useful to know while you are designing your printed piece and before it goes to press.

What can you do to avoid problems?

  1. Put crossovers on center spreads of signatures to avoid the need for precise alignment.
  2. Keep type 3/8" from the trim. In this way you can avoid type being cut through or falling too close to the edge of the paper.
  3. In producing saddle-stitched books, discuss "creep" with your printer. In multi-page saddle-stitched publications, type in the centermost pages of the nested signatures will be much closer to the face trim than will type in the same position either to the front or back of the book. This is called "creep" or "shingling," and your printer can help you adjust for it.
  4. Set up your files to allow for slightly shorter interior panels when creating a barrel-fold brochure. (Discuss specifics with your printer.)
  5. When possible, keep folds "balanced" (with edges touching, not with one shorter and one longer).
  6. Avoid designing a printed piece with more than five folds.
  7. To ensure that all pages lie flat, and to avoid cracks and wrinkles, make sure the paper grain lies parallel to the binding edge or spine.
  8. When in doubt, discuss your folding needs with your printer--early in the process.

[Steven Waxman is a printing consultant. He teaches corporations how to save money buying printing, brokers printing services, and teaches prepress techniques. Steven has been in the printing industry for thirty-three years working as a writer, editor, print buyer, photographer, graphic designer, art director, and production manager.]