Kompenzacija metamerije promjenama vrijednosti R, G I B kanala kod portretnih fotografija s točno definiranom pozadinom

Željko Bosančić1, Ivana Pavlović1, Mile Matijević1

zeljko.bosancic@grf.hr, ivana.pavlovic@grf.hr, mile.matijević@grf.hr
1Sveučilište u Zagrebu Grafički fakultet, Getaldićeva 2, Zagreb, Hrvatska

Sažetak

Portret je od početka fotografije do danas jedan od najčešćih fotografskih motiva. Kroz povijest, a i danas aktivno potiče razvoj fotografskih sustava i tehnika. Danas se fotografski portreti konzumiraju u različitim svjetlosnim uvjetima definiranim, uz ostalo, temperaturom svjetla, što bitno utječe na njihov doživljaj. Niz ispitivanja je pokazao kako čak i malene promjene vrijednosti (unutar 10%) R, G i B kanala (crveni, zeleni i plavi kanal) pri reprodukciji ljudske kože uvelike utječu na doživljaj portreta. Tako i promatranje u različitim uvjetima, također utječe na percepciju, odnosno poruku koju portretna fotografija prenosi. U ovom radu se ispituje mogućnost kompenzacije, tako nastalih metamerijskih promjena boja kože kod portretnih fotografija sa standardnom pozadinom, uz standardne izvore svjetla točno određenim promjenama R, G i B vrijednosti digitalnog zapisa fotografije.
Ključne riječi: portretna fotografija, RGB kanali, metamerija, izvori svjetla

Compensation of metamerism by changing RGB channels in portrait photography with a predefined background

Abstract

Since the beginning of photography portrait was on of the most frequent photographic motives. Throughout history but also today it encourages development of photographic systems and techniques. Photographic portraits are today consumed in various lighting conditions defined by the temperature of light which significantly affects the experience. A set of previous tests has shown that even a slight change in values (within 10%) of R, G, B channels (red, green and blue) in reproduction of skin colors affects the experience of a portrait. In such a way different lighting conditions can affect perception and the message of a portrait photography. This paper examines the possibility of compensation metameric changes of skin color in portrait photography with a standard background, standard light sources using specific changes in R, G, and B values of the digital photographic images.
Keywords: portrait photography, RGB channels, metamerism, light sources

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