UV-cut (In French filtre anti-UV) filter in colorimetric measuring instruments which filters out the UV component from the irradiated light to be measured; application: comparison to measurements with UV component for the purpose of evaluating the optical brighteners in papers and printing inks.
UV curing (In French séchage sous UV) application of the short-wave invisible range of optical radiation for drying printing inks, inkjet inks and varnishes (hardening of the layers); UV-C (280 to 100 nm) starts the radically or cationically induced crosslinking reaction by splitting up the photoinitiators, UV-B (315 to 280 nm) maintains the radical polymerization, UV-A (380 to 315 nm) penetrates thick layers. UV inks are preferably printed on smooth, non-absorbing surfaces (plastics, metalized substrates)…
under-color removal see UCR.
under-color addition (In French ajout de sous-couleurs) see UCA.
Ulbricht sphere spectrophotometer (In French spectrophotomètre à sphère) device whose purely diffuse measuring geometry (di:8° or di:0°) makes it possible to measure colors on high-gloss and curved surfaces as well as surfaces with metal and interference effect pigments, where devices with 45°:0° geometry fail. Color measurement results obtained using different measuring geometries are not comparable.
UCS, Uniform Chromaticity Scale see CIELUV.
UCR, under color removal (In French ajout de sous-couleurs) modified chromatic composition in which the CMY components (tertiary colors) jointly involved in the shadow areas of the image (three-quarter to full tones) are replaced by a “short black”. The purpose is the reduction of the total ink coverage to significantly less than 400% to prevent drying and wet-on-wet ink trapping problems. When this reduction is extended to all areas of the three-color gray, this is…
UCL, Universal Color Language (In French langage universel des couleurs) basis for understanding introduced in 1965 by K.L. Kelly and improved in 1976 concerning color names, compiled in a dictionary; with terms, among others, like bright, pale, strong.
UCA, under color addition (In French ajout de sous-couleurs) process within achromatic composition to compensate for its deficits in brilliance and contrast; in this process, small quantities of the under colors CMY, which had previously been reduced to zero, are increased again in the “under colors” (neutral image depths and three-quarter tones), leading to an improvement in black. This also leads to a smooth transition to the chromatic color separation with UCR.
TVI AVT see dot gain.
truecolor file (In French fichier truecolor) image file with 8 bit per pixel per color channel R, G, B; theoretically, 23×8 = 16777216 hues can be represented.
tritanomaly (In French tritanomalie) color vision deficiency; blue receptor weakness, blue-yellow metamerism.
tristimulus measurement, trichromatic colorimetry (In French mesure trichromatique) see colorimeter.
tristimulus color space, CIE color[imetric] system, CIE XYZ system of color space vectors (color stimuli) that were derived from the color perception primary stimuli RGB in order to bring together physiological color vision and the physical color stimulus causes. X is derived from R (retinal receptors generating red), Y from G (green) and Z from B (blue). The tristimulus color space represents the totality of all perceptible colors, but is purely mathematically constructed and thus…
trichromatic vision (In French trichromasie) normal vision, correct color daytime vision with the 3 fundamental stimuli PDT.
transparent inks (In French encres transparentes) printing inks for multicolor screen printing. The glazing behavior, i.e. the medium covering ability, is a precondition for the functioning of the autotypical color blending in which not only side by side printing but also overprinting of the halftone dots (and solid areas), including paper white, flows into the result. Example: Overprinting the solid areas of yellow on magenta creates red, because yellow lets through radiation elements of magenta.
transparency (In French transparence) property of being able to see through foils, filters and other media which allow a more or less clear view through them. Application: color filter, polarizing filter.
transmitted colors (In French couleurs par transparence) surface colors of clearly transparent objects (e.g. glass, color filter).
transmission (In French transmission) passage of light through a transparent medium; counterpart to remission on opaque surfaces.
translucency (In French translucidité) shine through of light, e.g. translucent paper.
