Glossary of terms

Technical terms simply explained

Abney’s law loi d’Abney the luminance L of a displayed RGB color shade is composed of the primary valences R, G, B with their respective luminance coefficients: In the standard CIEXYZ valence system, for reasons of mathematical simplicity, the standard chromatic values X and Z make no contribution to brightness, but only Y, so that Y itself can be interpreted there as brightness.

abrasion/rub resistance résistance à l’abrasion abrasion resistance of the dried printing ink layer or the overprint coating; necessary property of uncoated folding boxes and magazine covers.

absolute white standard/reference étalon blanc ceramic sample with completely matt white surface, whose known colorimetric values are used during calibration as a reference for spectral measuring devices; each color measurement by the device is then placed in relationship to the absolute white standard; the absolute white standard must be protected from dirt.

absorption, absorptive attenuation absorption 1) lat. “suck in”; weakening (going as far as removal) of certain spectral components of the radiated light as it passes through a medium or strikes a brightly colored surface; through a., colored inks, printing inks and toners develop the desired colored effect; a. is responsible for “subtractive color mixing”; 2) absorption of ink by the substrate, leading to the drying of suitable printing ink layers.

absorption factor, absorptance, absorptivity coefficient d’absorption, absorptivité ratio of absorbed to total incident radiant energy; may be applied as a curve α(λ) over the wavelength λ (spectral a.).

absorption-to-scattering ratio, A/S coefficient d’absorption et de diffusion, K/S basic equation developed in the 2-component theory of Kubelka and Munk in 1931 for the mixture of opaque color layers; ratio of A (concentration-dependent absorption degree of the color layer) to S (scatter behavior of the color layer, depending on the reflection degree R), calculated across the entire visible spectrum: For the Kubelka-Munk equation to be used for the development of recipes for transparent inks as well, there must be sufficiently thick color layers of the components to be mixed so that a spectrophotometric measurement can be carried out without any influence being exercised by the substrate. Color mixing and developing software using refining algorithms determine the concentrations c of the basic inks to be mixed, and any other remaining inks to be used

additive color mixing Example of superimposing red, green and blue spots. Pairwise superposition generates the secondary colors CMY, complete superposition leads to an achromatic shade (maximum: white).

additive color mixture/synthesis synthèse additive mixing principle of superimposing light colors through the addition of their components to form a color shade with greater brightness; primary colors Red-orange, Green), Blue-violet; secondary colors R+G=Yellow, R+B=Magenta, G+B=Cyan; maximum possible mixing result with sufficiently bright equal components is white, which is created by the addition of the primary colors W=R+G+B or of the two respective complementary colors  W=R+C=G+M=B+Y; light colors are mixed for example with spotlights from light sources with colored filters placed in front of them, with light dots placed close to each other (monitor RGB pixels), but also with a rotating circle with different-colored surfaces; the spectral characteristics of the individual light colors cannot be inferred from the mixing result (Grassmann’s 3rd Law).

additives additifs, adjuvants substances to influence the properties of printing inks, e.g. drying substances, antioxidants, waxes (for greater abrasive strength), plasticizers, flow agents (viscosity), anti-foam agents (for screen rollers), antistatic roller agents etc.

adjacent juxtaposition typical arrangement of two color matching samples in the field of vision to carry out the color comparison without the influence of contours and other surrounding colors.

adjustment ajustement the implementation of basic settings in measuring devices through exact positioning and internal value matching.

after-image contrast contraste successif after-image appearing in the respective complementary color which color stimuli leave on the retina for some seconds (perceptible by closing the eyes) and which have an adverse effect on the ability to evaluate colors. Consideration in practice: When matching different pairs of colors, the eyes should be given longer relaxation breaks between the color comparisons by
having them look at a gray surface – comparable with white bread during wine tasting.

ageing vieillissement 1) Property of light sources to lose brightness with increasing service life, with its spectrum also shifting; bulbs and fluorescent lamps are more severely affected than LEDs, which is why the latter are being used more and more as steady standard light sources (see Just). 2) Long term process of chemical decomposition of layers of ink through external influences, e.g. solar radiation, rainwater,

alpha channel canal alpha in image editing programs, besides the color channel, additional channels (1 or more) in which transparency information is defined with 8 bits per pixel (RGBA); the values range from 0 (transparent) to 1 (opaque).

anilox roller rouleau/cylindre anilox designation for ink and varnish feed rollers whose origin is in former flexo printing with “aniline dyes”; the screen-type engraved ceramic surface (“screen roller”) has also proved to be advantageous in water-less offset short inking units (KBA Gravuflow/Newsflow, KBAMetroPrint), since the ink key control of inking is implemented through the viscosity-dependent ink transfer quantity with the help of a tempering device.

anilox screen trame aniloxe dot structure on inking roller in flexo printing and waterless offset printing with short inking units (KBA technology).

ANSI US standards institute; developed the IT8 targets in color management, among other things.

appraisement, appraisal évaluation technical or visual comparison between reference and sample; the result is a color difference Delta E.

approved press sheet, OK sheet BAT, bon à rouler, bonne feuille, épreuve acceptée sheet printed at the end of the setup of the production printing press, approved as a visual and metrological production print reference. assessment appréciation the Delta E detected is assigned to categories by means of predefined tolerance intervals, e.g. “unnoticeable”, “small” or “large”.

ASTM American Society for Testing Materials US institution, which among other things develops test methods for inks, e.g. D387:2008 (standard test for the color and strength of pigments) or WK20008 (block resistance).

automatic/closed-loop color density control régulation de l’encrage automatic control of color density in printing presses, integrating color measurement or color density measurement in a closed signal flow circuit, e.g. KBA QualiTronic ColorControl.

autotypical color mixture, halftone color synthesis synthèse autotypique optical effect combination of additive and physical color mixtures of transparent to opaque inks when they are printed adjacently or partly overlapping, in the form of periodical (AM) or non-periodical (FM) screens. The additive mixing effect (preferably adjacent printing) diminishes as the absorptive mixing effect (preferably superimposed printing) increases. The basic colors in the standard process are the additive secondary colors Cyan], Magenta] and Yellow plus drawing black Key and paper white White – described for the first time in the “Neugebauer equations” (see History); standard process mixed colors are M+Y=Red orange, C+Y=Green and C+M=Blue violet, C+M+Y=Gray. The effect is also displaced by effects of light diffusion (absorptionto-scatter ratio).