luminous energy (In French quantité de lumière) light energy times time in lumen seconds [lm·s]

luminous efficiency/yield (In French efficacité lumineuse) the minimum relationship between radiated and received luminous flux required for successful color measurement.

luminous efficiency function (In French courbe d’efficacité lumineuse) describes the spectral luminous efficiency of the human eye in daylight for the 2° standard observer. The maximum in green is 555 nanometers. The luminous efficiency function also explains why human beings can distinguish more green color shades than red or blue, why “green” is good for the eyes and why green coats are usually worn in the operating theater.

luminescent diode (In French diode électroluminescente) see LED

luminescent colors (In French couleurs luminescentes) color stimuli of self-luminant bodies (lamps, monitors, data projectors); see also additive color blending; opposite: surface colors.

luminescence scanner (In French détecteur de luminescence) detector for the presence of fluorescent pigments in printing inks and optical brighteners in paper, e.g. from Leuze, Sick.

luminescence (In French luminescence) the ability of solids, liquids or gases to emit light of a certain wavelength spectrum during the transition from a stimulated state to a basic state. The emission of light always requires an internal or external stimulation: through electric current (LEDs, OLEDs), light particles (phosphorescence: afterglow; fluorescence: real-time luminescence), chemical reactions (luminol in forensic medicine, luciferin in glowworms), heat input (embers), X-rays (projection screen), amplification through stimulated emission (laser) etc.

luminance factors (In French facteurs de luminance) standardized values for brightness signal formation in color television; the following applies for the 3 color channels RGB: “luma -red” = 0.299, “lumagreen” = 0.587 and “lumablue” = 0.114.

luminance factor (In French facteur de luminance) value A for marking the brightness of a surface color, independent of the color ordering system and thus comparable between systems; in CIEXYZ A is equated with the Y stimulus (green).

luminance (In French luminance) SI unit: candela per square meter [cd/m²]; non-SI units: Apostilb (asb), Blondel, Bril, Lambert (la), International Stilb (isb), Skot (sk), Stilb (sb); see also brightness

lumen (In French lumen) see luminous flux

lpi, lines per inch (In French lignes par pouce) see definition

low-migration ink (In French encre à faible migration) classification of a printing ink when the permissible SML values (“specific migration limit”, in mg material per kg food) of all substances that have an adverse effect on the smell/taste/appearance of the packed substance (test substance: modified polyphenylene oxide, Tenax) fall below permissible limits (DIN EN 14338/1186-13).

look-up table (In French table de correspondance) see CLUT

long key/black (In French noir long) in the UCR-modified chromatic composition with gray component replacement GCR, the use of the achromatic process color black instead of the three chromatic colors CMY, in a wide section of the tone value range, that is, with a low starting point.

long color (In French encre longue) see ink stringing

LMS color space (In French espace LMC) see fundamental stimulus

liquid-crystal color display (In French écran à cristaux liquides) see active matrix display

linearization (In French linéarisation) procedure in the calibration of digital printing systems and inkjet digital proof printers. Here, with the help of a spectrodensitometer, e.g. Techkon Spectro- Dens/SpectroJet, a control strip provided for the linearization, e.g. ECI Gray Control Strip, is recorded on a printed sheet in order to be able to adapt the actual values to the target values. This option is also available on offset-print copies printedunder PSO/ISO-standardized conditions; there, the “GrayCon strips”…

line work , LW (In French dessin au trait) monochrome pixel graphics file with 1 bit color depth, i.e. binary status “hue” and “no hue”.