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FLEXO Magazine : July 2009
DESIGN Revectorized Files Files that were created on a Mac, converted to a high-end system, and then converted back to a Mac are called “revectorized.” If possible, these files should not be used. If these files are used, they should be simplified as much as possible. When a RIP converted the file to raster, the RIP decided which pixels to turn on, using the PostScript information sent by the application. Now another program has processed it, making more decisions about where to place nodes, making this a third-generation image. Some change is inevitable; in the best case, it may be in the range of 0.001” (0.025 mm). For best results, use this image for position and move or adjust the original art to fit. Recreate the art whenever possible; that is, redraw the elements in the program to create new elements that are native to the program. This solves the file size issue and produces elements that are easily incorporated into future designs and changes. 4.5 Blends, Vignettes, Gradations The terms blend, vignette, gradation, fade-away, fountain, and graduated tint are used interchangeably. FIRST uses the term vignette for clarity. Building A Vignette There are several approaches to building a smooth vignette as well as multiple problems in creating vignettes. Some of the approaches concern the way they print, others concern the way they are specified in software programs. Vignettes are subject to unpleasant banding (steps where tints do not transition smoothly) or dropping off (leaving a hard edge). Improvements in software have resulted in improved quality vignettes. Although the algorithms used to create vignettes have improved, they still require skill and careful planning. A thorough understanding of current software applications and the printers’ capabilities are required to create a printable vignette. Generally, the prepress provider is best equipped to create the vignette contained in the final production file. Some of the primary considerations when building a vignette include: Blending One Spot Color Into Another: When blending one spot color into another spot color, two final files should be produced: a file for creating a comprehensive proof (color comp) and a file for production. The production file must contain two separate vignettes, one for each color. Mark up a proof with instructions for how the vignette is to be created in addition to including instructions on the annotation layer. For example, “100% to 20% yellow overprinting 40% to 80% navy.” There is no easy way to create one file that shows this effect and prints the correct tints except with process colors. Another solution is to substitute process colors for custom colors; for example, the magenta channel might print as red, the cyan as reflex blue, the yellow as gold and the black as green, etc. Blending A Spot Color into White: When creating a vignette of a spot color fading to white, specify the minimum dot percentage of the spot color on the lighter end of the vignette. One technique is to use the same spot color for both ends of the vignette. One end should be set to the full tint value while the other end should be set to the printer’s minimum dot size in the same color. Trapping Vignettes: Vignettes are difficult to trap. The lighter color should trap into the darker color, but that relationship changes in a vignette. When placing type or graphics over a vignette, be aware that when the necessary trapping is applied, undesirable results may occur. RIPping Vignettes: Designs that use multiple vignettes will take longer to process. To facilitate processing, consider using a raster program for the continuous tone image – the part of the design that looks like a picture. Use vector files for type and other elements that need hard, clear edges or very fine detail. Some processors will RIP vignettes from drawing programs to a continuous tone and add noise to prevent banding. This allows the prepress provider to separate the art, but requires more time to RIP. Radial Vignette Linear Vignette S. Gilbert 4.5a: Radial & Linear Vignettes: A holding line around a vignette protects the smallest highlight dots and helps to prevent hard edges and dirty print.
Sustainable Spring 2009