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.0 nm (red).On the basis of comprehensive statistical investigations, these valueswere established as representing the color perception of the"standard colorimetric oberserver".The standard colorimetric system describes colors as vectors in athree-dimensional model (color space).A radius vector originating fromthe zero point (or black point) is assigned to each chromaticity.Eachchromaticity thus has its own direction in the color space.The radiusvector of a given color in the color space is called the colorstimulus.A color stimulus is the equivalent, expressed numerically, ofthe physiological sensation of color of a "standard observer"with normal color vision.The mathematical simulation of the assessmentof a radiation stimulus through the eye and brain converts thisstimulus into a color stimulus, which can be unambiguously described bythree factors, e.g.hue, saturation and brightness.The vectorproperties of color stimuli enable colors with two or more vectors tobe additively combined from three fixed primary color stimuli(according to the principles of vectorial addition).The CIE system is an important scientific method of coloridentification because it is so close to the human perception of colorand because of the possibilities it offers for accurate mathematicaltreatment of spectrophotometric data.The complex vectorial representation in the color space is replaced inpractice by a simplified, two-dimensional representation of the colorse.g.in CIELAB diagrams. Core shell crystalsAgfa-Gevaert began researching core shell silver halide crystals backin 1960 and recently developed them a stage further.The core and theshell have different halide compositions.One special form is termed"structured twin crystal".As a rule, these are silver halide crystals consisting of a core with ahigh silver iodide content and an exterior shell of silver bromide witha low silver iodide content.Such crystal structures, which aremanufactured both in flat platelet form (like the T grains from Kodak)and in compact form, intensify the developable silver blackening perunit of incident light (it is therefore also possible to talk of"increased quantum efficiency").Special manufacturing methods reduce the formation of excessively smallcrystals, which would impair the sharpness due to light scattering(fine grain is not necessarily equivalent to high sharpness, and oflarge crystals, which would result in the grain becoming coarser (crystal technology).Fig.5: Example of a special core shellcrystal. ColorColor is not an absolute characteristic of an object, but a humanperception.The color stimulants registered by the retina of the eyeare made up of the energy distribution and the spectral properties ofthe visible light passing through or reflected by an object.Thesensation of "color" only comes about after a complexoperation in which the brain processes the information relating to theincoming stimuli.The photoreceptors of the retina (rods and cones) convert light intonerve impulses.Three kinds of cones with different sensitivities fordifferent wavelengths are responsible for color vision, i.e.respondingto stimuli in the visible spectrum.The ability to see colors is, overa broad range, independent of the brightness of the visible light(range of photopic vision).In the case of radiation-sensitive systems, e.g.measuring devices,photographic films, printing materials and the human eye, we talk notof "color sensitivity", but of spectral sensitivity. previous alphabetic indexnext Photohome- Agfa Library - Technical Terms - "C" <-- you'rehereAboutAgfa | Agfa Arcade | Agfahome | PhotohomeSearch | News | FeedbackAgfa Photo Gallery | Advanced Photo System | Trends & Experiences | Products©1996 by Agfa-Gevaert AG, Copyright and TrademarkInformation
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