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FLEXO Magazine : July 2009
DESIGN Factors Influencing Banding Many factors that influence banding in a vignette relate to the construction of the vignette. There is a mathematical relationship between the length, range, and the number of steps in a vignette. The length refers to the physical length of the vignette and the range refers to the difference in color across or down the vignette. For example, a vignette of 30% to 50% has a range of 20%. The longer the vignette, the more likely it is to show banding. The shorter the range of the vignette, the more likely it is to show banding. The fewer steps used, the greater the potential for banding. Banding is more visible with darker inks. Lower screen rulings are less likely to show banding. Higher output resolutions may also help reduce banding that may appear on some low-resolution printers and computer monitors. Professional film and direct-to-plate output devices usually run at a resolution of least at 1,200 dpi, which also helps minimize banding. If objectionable banding is observed when creating the file, make a notation on the annotation layer of the file, transferring the final inspection responsibility to the party outputting the file. Factors Influencing Hard Edges & Dirty Print To avoid hard edges and dirty print, it is important to maintain the printer’s minimum dot and not fade to zero. The printer specifies the minimum dot used along the edge of any vignette. The lightest area of the vignette should adjoin a holding line or the edge of a graphic window; this will ensure that hard edges or dirty print do not appear across the vignette when the dot fades to the printer’s minimum. When vignettes are made of more than one color, all colors must stop at the same place in order to prevent rainbowing and dirty print throughout the vignette. 4.6 Imported Images – Follow the Links File names are a critical reference link between the document and the image file. After placing an image, do not rename the files. All images placed in the document must travel with the document for output. Most layout programs treat imported images as electronic “pickups” and refer back (by following the link) to the image file at output. Always make certain that all links are updated properly before sending files. If an imported image is modified, always update it in the final document to make sure that it has not shifted position. FIRST recommends working with the appropriate packaging application. Problems, such as nested files, can be encountered when working outside of those applications. In many programs, it is an option to embed the placed image data with the EPS file. This is not recommended because some editing may be required downstream. Sending the native application files enables future changes. 4.5b: Building a Vignette: There are several approaches to building a smooth vignette as well as multiple problems in creating vignettes. 4.6: Imported Images: After placing an image, do not rename the files. File names are a critical reference link between the document and the image file.
Sustainable Spring 2009