The Very Last Designer's Guide to Digital, On-Demand, and Variable-Data Color Printing

1. Printing Issues
   1. Adjust your Expectations – digital presses will not reproduce images the same way that a conventional offset press will. Digital printing is a different technology. Its main purpose is to perform variable imaging and short run printing. Each piece can be different.
   2. Four types of digital presses in current use:
      1. Webfed dry toner
      2. Sheetfed dry toner
      3. Webfed liquid toner
      4. Sheetfed liquid toner
   3. DI presses are NOT digital presses. They are direct imaging presses. They do not recreate the piece each time like a true digital press.
   4. Digital presses will have a much lower resolution. You are much more likely to see spots, dots, and pixels. HP Indigo 3000 prints from 145 - 180 lines with no dot gain.
   5. Toner behaves differently on paper than ink does and usually sits on the surface.
   6. Liquid ink digital presses print very clean and takes on the quality of the paper.
   7. Blends, vignettes, and gradients are a challenge because of the limitations in the half toning process. Banding is likely to occur because of the limited resolution. To avoid problems, use tint values with a fairly wide range and "add noise".
      
      
2. Image Issues
   1. Avoid using JPEGs and GIFs.
   2. Colors should be converted into CMYK TIFF or EPS format. EPS files made from QuarkXpress do not save the fonts. Black-and-white images that have a tint in them should be saved as "grayscale".
   3. All scaling and rotating of images should be done prior to the file going to the printer.
      
      
3. Color Issues
   1. Convert all colors to CMYK.
   2. Total ink coverage of any given area on the sheet should not exceed 300%.
   3. Reduce the amount of dot gain in the file to 10%.
   4. Metallic inks cannot be used.
      
      
4. Paper Issues
   1. Coated papers generally print best.
   2. Uncoated papers can be used but will greatly exaggerate the deficiencies of a toner system (dry or liquid) in areas of heavy coverage or large areas of solids or screened tints.
   3. Trapping is not usually an issue with digital presses.
   4. Digital presses require a bleed of 1/8 inch.
   5. Toner may crack or flake when the paper is folded because the paper does not absorb it. It sits on top.
   6. Liquid ink digital press has less of a problem with cracking.
   7. Heavy toner coverage on both sides may cause the paper to curl. May also cause the toner to appear glossy.
   8. Liquid ink digital press does not tend to curl.
   9. Typically uses a slightly heavier weight paper.
      
      
5. Text Issues
   1. Always include the fonts used.
   2. Type that is reversed out of a colored background, or type that requires high resolution for maximum clarity will not look good when printed digitally.
   3. Do not use any type smaller than 6 points. Reversed type should not be any smaller than 9 points and then only if it is a sturdy sans-serif typeface like Futura or Universe. Serif type should never be set in a reverse for digital printing unless it’s over 12 points.
   4. Very thin, fine lines may disappear or may appear slightly jagged on curves.
      
      
6. Variable-Data Issues
   1. All images must be at the right size, orientation, and crop.
   2. All files for variable images must exist in TIFF or EPS format and all variable files use the same format.
   3. The difference between variable-data printing and a simple mail merge is the ability to use images and artwork as variable elements in addition to the text.
      
      
7. Ten Rules of Digital Printing Design
   1. Utilize Strengths and stay away from its weaknesses.
   2. Pick your paper from papers available for the specific digital press. Characteristics for good paper match include acid free and ph balanced sheets. Typically archival stock types work for electro static printing.
   3. Watch for registration front to back. Be aware of the specifications of the output device. Many digital presses do a good job duplexing.
   4. Use of spot color. Most toner based digital presses use CMYK for spot colors. HP Indigo 3000 includes 6-color option that includes PMS colors and customer color match.
   5. Watch flat colors and gradients. Blends, vignettes, and gradients are a challenge because of the limitations in the half toning process. Banding can occur because of the resolution. To avoid problems, use tint values with a fairly wide range and “add noise”.
   6. Watch your monitor closely. Understand the equipment’s limitations. Color corrections done on the press are global changes done all across the entire sheet, front and back. Spot corrections are best corrected on the file. Color proofs provided before the project is printed will be key.
   7. Choose the right software. Check with your vendor on the specific requirements. Create items with Illustrator, FreeHand and Photoshop then import them all into QuarkXPress. Convert all artwork to CMYK.
   8. Package for output. Be sure to include all fonts and linked graphics files (and don’t embed the graphics by cutting and pasting). Save file in the proper format. Digital printing companies prefer to use PostScript Type 1 fonts and that you set the trapping to none. PDF files are fine for static projects. Variable data file projects prefer Quark files.
   9. Finishing Options. Toner unlike liquid ink sits on top of the paper and tends to crack on folds. Liquid ink has less of a problem. Options are to avoid printing across folds, use light coverage in fold areas and watch grain direction of the paper. Cover grain is short and text grain is long. Coating the final piece is effective in dealing with cracking issues.
   10. Know the target output device. Each digital printer and press has unique characteristics. Contact the vendor to find out specifics. Variable data files require special set up over a static piece.