lightness, luminance (In French clarté, luminance) luminance L in candela per square meter [cd/m²], strength of a light perception. Each color sensation is also associated with a lightness sensation, i.e. the luminance channel light–dark supplements the two chrominance channels red–green and blue–yellow, e.g. L* in the CIELAB/CIELCH color space model.
lighting conditions (In French conditions d’éclairage) technical conditions prevailing during a color stimulus; these include the illuminant of the source, the influence of the surroundings (neutral or colored, stray light) and the angle of observation (glare and reflection-free).
light source (In French source lumineuse) any self-luminant body
light scattering (In French dispersion de la lumière) on rough/matt surfaces the effect of diffuse reflection, which causes a chaotic distribution of the radiated light. In the measurement of color and color density, only the share of scattered light is registered.
light gathering/trap (In French captage de la lumière) phenomenon in halftone printing in which incident light, in its reflection in the upper layers of the substrate, is prevented from leaving the substrate, because the printing ink layer of the halftone dot blocks the way; this occurs mainly in substrates with low opacity and increases the tonal value increase of the halftone print. The strength of the effect is also dependent on the screen ruling (screen…
light fastness (In French solidité à la lumière) ageing stability of pigments and dyes vis-à-vis UV rays in natural daylight (simulated with xenon high-pressure lamps in accordance with ISO 12040, determined as fade resistance (résistance à la décoloration) of the Blue Wool Scale in accordance with DIN EN ISO 105-B01).
light (In French lumière) wavelength range of the visible radiation of the electromagnetic spectrum, approx. 380 to 780 nanometers.
LED, light-emitting diode (In French DEL diode électroluminescente) semiconductor light source which, depending on its design, can emit narrow to broadband wavelength ranges. Examples of applications: Imaging of photoconductive drums in digital printing systems, light source in spectral measuring devices as an alternative to the gas-filled light bulb, simulation of random illuminants in color-matching booths (patent: Just Normlicht), backlighting of LCD monitors and television sets.
LCH, lightness–chroma–hue (In French clarté) – chroma – teinte see CIELAB
LCD, liquid-crystal display (In French écran à cristaux liquides) see active matrix display
laser diode, LD (In French diode) laser semiconductor radiation source related to the LED, with emission ranges in the infrared, red, and violet ranges; applications include the illustration of printing plates.
laser, light amplification by stimulated emission of radiation (in French laser) technical light source with special properties of the emitted rays: 1. monochromatic (extremely narrow-band wavelength range, to be limited exactly to 0.1 nanometers), 2. coherent (predictable route and interference properties through high constancy of the wavelength, important for example in distance measuring, holography); 3. parallel (ideal bundling capacity for high energy densities); thus numerous possible applications, including printing forme illustration, laser printing (photoconductive drum),…
Kubelka-Munk see absorption-to-scattering ratio
Küppers’ color theory (in French théorie des couleurs de Küppers) theory of color perception and color rendering developed by Harald Küppers, not based on CIE recommendations or DIN standards and for this and other reasons controversial; Küppers redefined the maxima of the 3 cone sensitivity levels, unlike the CIE values 1931, namely 448 nm for blue (V, “violet blue”), 518 nm for green (G) and 617 nm for red (O, “orange red”). On this he…
What is after-image contrast? After-image contrast (In French 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…
What is keyless inking, short ink-train technology? Keyless inking, short ink-train technology (In French technologie d’encrage court) process group adapted by KBA from flexoprinting for offset printing and optimized for waterless offset (sheet-fed offset: Gravuflow and MetroPrint, coldset: Newsflow) for non-ghosting print forme coloring; features: keyless blade chamber instead of ink duct, temperature-adjustable screen roller instead of fountain roller, ink forme roller(s) with blanket instead of ductor roller, distributor drum (except Newsflow) and rubber rollers, temperature-adjustable plate cylinder.
What is Kelvin? Kelvin (In French kelvin) SI unit of measure K (without ° symbol) named after the British physicist William Thomson Kelvin of Largs for the absolute temperature T. With color temperatures, conversion into °C or °F is not permissible. Learn more about kelvin and the index of natural and artificial light.
What is “K?” “K” international abbreviation for the achromatic process printing ink black (“key”). Learn more about the CMYK color model.
What is just covering ink quantity? Just covering ink quantity (In French seuil de couverture ink quantity) (in g/m²) required to create a solid film of printing ink on the substrate; indirect measure for substrate smoothness, for the lower the just covering ink quantity, the greater the smoothness.
What is JPEG, Joint Photographic Expert Group? JPEG, Joint Photographic Expert Group CCITT/ISO group of experts that developed the compressible pixel graphic format JFIF (JPEG File Interchange Format, .jpg) and a related video procedure (Motion JPEG, MJPEG, MP4). The greater the compression, the greater the information loss, which becomes apparent through annoying artefacts in the image; even when the JPEG file is available in RGB, it is internally coded according to the YCC color model in the color…
