[ Pobierz całość w formacie PDF ]
.What is meant is the expression"opposite color", since it refers to the colors that areopposite each other in the color circle.Strictly speaking, pairs ofcolors which produce white as an additive color mixture arecomplementary. Contrast gradeThe contrast grade (gradation) describes the level of contrast of aphotographic material.A material with flat gradation converts highcontrasts in the subjekt (marked differences in luminance) into lowimage contrasts.In this way it is possible, for example, to photographthe broad range of tonal values of a sunlit landscape.The slope angleof a flat gradation curve is less than 45°.A material with steepgradation, on the other hand, can translate low brightness contrasts inthe subject (e.g.misty landscapes) into higher image contrasts.Theslope angle of a steep gradation curve is greater than 45°. Cross castcolor shifts become apparent either as a color cast or as a cross cast.A color cast results from one of the three color density curves (oncondition they have been standardized to gray* being flatter or steeperthan the other two curves.A color cast can be eliminated by suitablecorrection filtering.A cross cast is the result of one of the threecolor density curves being intersected by one of the others, with theresult that one of the three curves is higher in the area of minimumdensity and, at the same time, lower in the area of maximum densitythan the other two curves (it can also happen the other way round witha lower minimum density and a higher maximum density).This can mean,for example, that the highlights - with neutral filtering of the mediumtones - can have a complementary color cast to the shadows (complementary colors).Unlike acolor cast, a cross cast cannot be eliminated by correction filtering,since color correction filtering of the highlights would lead to anintensification of the complementary color cast in the shadow areas.* Contrary to common opinion thatnon-parallel color density curves or different gamma values for yellow,magenta or cyan always lead to color casts (color defect of the firstorder) or to cross casts (color defect of the second order), it shouldbe pointed out that the integrally measured color density curves of acolor negative film, for example, merely state that the film printsneutrally on a defined positive printing material under suitablelighting and with suitable filtering in the highlights and shadows.Thegrey-equivalent values for the color density curves of a color negativefilm are thus not related to the human eye, but are neutral from aprinting point of view (grayequivalence). Crystal technologyThe basis of all photography are the silver halide microcrystals, whichare often smaller than 1/1000 mm.They are photosensitive and are thesmallest elements for storing the optical information.The silver halide crystals of the very latest generation as used byAgfa - they are also called structured twin crystals - measure between0.2 and 0.3 thousandth of a millimeter.Because of their specialstructure (core shell crystals)they absorb more light than conventional crystals.Some light isinevitably scattered on the crystals and produces halos (= loss ofsharpness), but the effect is much reduced with the new silver halidecrystals, minimizing the loss of sharpness.Flat, thin crystals can also be packed more densely.This enables theemulsion layers to be made thinner without sacrificing any of theirsensitivity: the thinner the emulsion layer, the better the sharpnessof the film.On the other hand, many more crystals can be accommodatedin the emulsion layer without increasing the layer thickness.Thismakes the film very much faster without having any negative influenceon the graininess.Summarizing, structured twin crystals bring about animprovement in sharpness and grain in relation to the film speed. 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
[ Pobierz całość w formacie PDF ]