The contribution of luminance and chromatic channels to color assimilation

Luminance; Chromatic channelsLuminancia; Canales cromáticosLluminància; Canals cromàticsColor induction is the phenomenon where the physical and the perceived colors of an object differ owing to the color distribution and the spatial configuration of the surrounding objects. Previous works studying this phenomenon on the lsY MacLeod–Boynton color space, show that color assimilation is present only when the magnocellular pathway (i.e., the Y axis) is activated (i.e., when there are luminance differences). Concretely, the authors showed that the effect is mainly induced by the koniocellular pathway (s axis), but not by the parvocellular pathway (l axis), suggesting that when magnocellular pathway is activated it inhibits the koniocellular pathway. In the present work, we study whether parvo-, konio-, and magnocellular pathways may influence on each other through the color induction effect. Our results show that color assimilation does not depend on a chromatic–chromatic interaction, and that chromatic assimilation is driven by the interaction between luminance and chromatic channels (mainly the magno- and the koniocellular pathways). Our results also show that chromatic induction is greatly decreased when all three visual pathways are simultaneously activated, and that chromatic pathways could influence each other through the magnocellular (luminance) pathway. In addition, we observe that chromatic channels can influence the luminance channel, hence inducing a small brightness induction. All these results show that color induction is a highly complex process where interactions between the several visual pathways are yet unknown and should be studied in greater detail.Supported through the research projects: Grant PID2020-115734RB-C21 funded by MCIN/AEI/10.13039/501100011033 and Grant DPI2017-89867-C2-1-R funded by MCIN/AEI/10.13039/501100011033/ and FEDER Una manera de hacer Europa, by the Secretaria d'Universitats i Recerca del Departament d'Empresa i Coneixement de la Generalitat de Catalunya through 2017-SGR-649, and CERCA Programme/Generalitat de Catalunya

Estudi comparatiu del comportament perceptual de diferents algorismes Tone Mapping

D'experiments diferents per avaluar "tone mapping operators" se n'ha fet de molts tipus diferents i amb molts objectius diferents. Nosaltres, en aquest treball, hem realitzat experiments psicofísics sobre 15 algorismes "tone mapping" diferents per tal d'obtenir un ranking des del punt de vista de la percepció humana. Per aconseguir aquest ranking, hem realitzat dos experiments diferents: un per estudiar la relació de tonalitats de grisos en la imatge "tone mapped" i en l'escena HDR real i un "pairwise comparison" dels 15 algorismes, observant l'escena HDR real just al costat del monitor CRT calibrat. Els resultats dels experiments han demostrat que, pel primer experiment, iCAM és el millor amb diferència, mentre que pel segon experiment, els millors han estat Kraw i KimK.There are a lot of different experiments to evaluate tone mapping operators. In this work, we performed psycophysics experiments with 15 different tone mapping algorithms to obtain a human perceptual ranking. To achieve this ranking, we performed two different experiments: one to study the relationship between gray tones, and the other performed a pairwise comparison of these 15 algorithms. In the first one, we matched the gray tones in the tone mapped image and in the HDR real scene. In the second one, we performed a pairwise comparison of tone mapped images, while watching the HDR real scene next to the CRT calibrated display. We built a ranking from the pairwise comparison results using the Balanced Rank Estimation method implemented by Wauthier et al.(2013). The results of the experiments showed that iCAM is the best tone mapping operator for the first experiment, while Kraw and KimK are the best for the second one