Xerox P8EX Spire CXP8000 Color Server - User Guide - Page 444

430 Linework Metamerism Midtones Misregistration Moiré Newton's rings OPI Output resolution Spire CXP8000 Color Server User Guide Linework graphics are characterized by sharply defined lines and very clear transitions from one color to another. Linework is stored in the computer as a series of geometric (vector) drawing instructions. Metamerism occurs when two colors match under one light source, but appear different under another light source. Those two colors are called a metameric match. A metameric match might cause problems when trying to match proofs to press-sheets under different lighting conditions. Density values of an image (original or reproduction) between the highlights and the shadows. In the reproduction, midtones are printed with dot areas between approximately 40% or 60%. See also Highlights and Shadows. A situation common during printing where one or more of the color separations is slightly misaligned with regard to the others on press. Misregistration shows up as white gaps or tinted overlaps at the borders of color pairs. Colors containing such files are trapped to compensate for this possibility. On Continous Tone images, misregistration can lead to blurring. See also Overprint and Trapping. An interference pattern caused by differences in halftone screen angles or rulings. In process color printing, screen angles are selected to minimize this pattern. If the angles are not correct, a pattern that distracts the eye from the picture may be produced. Small concentric circles that can appear on film when two surfaces are closed together but not in perfect contact. Abbreviation of Open Prepress Interface. A prepress convention established by Aldus Corps. OPI refers to tags or place holders in source PostScript that point to TIFF or EPS images that have not been embedded in the PostScript. These images reside in other locations and are merged with the PostScript file when processed. Normally used for performing high res/low res image substitution (alternative to Creo APR). The number of laser dots per unit of linear measurement (millimeter, inch etc.) on film or paper.