PURPOSE: In middle-level visual mechanism, the important role of X-junction as one typical visual structure has been discussed in the haze illusion (Adelson, 2000) and typical perceptual transparency studies (Kitaoka, 2005; Koenderink, 2010) respectively. Under the combined effects of X-junctions, we find that there exists typical transparency perception in the haze illusion, but how the two lightness perception phenomena affect each other at the perceived level is still lack of empirical research.
METHODS:Subject: We build the visual experiments in a dark room with a LCD display to avoid the ambient light falling on the display screen. Five subjects all of normal vision participated: two experimenters and three volunteers naive to the experimental task. Procedure: In the typical constructed haze illusion with a changing additive factor, observers were firstly asked to judge the apparent haze state of the central regions from Hazy, Clear, and Paint. Then to determine whether the same region in the larger context with surrounding inducing X-junctions gave rise to perceptual transparency. The determination of apparent haze state with the perceptual transparency state forms the matching pair set.
RESULTS: The matching data shows, under the central and inducing X-junctions’ effects, the perceived state of evaluated regions not only changes from apparent clear to haze but also presents perceptual transparency in the process of additive factor changing. The synergy of both visual phenomena varies from different inducing X-junctions surround: non-reversing X-junctions strengthen effects both of the haze illusion and the transparency perception, single-reversing ones help to affect the haze illusion and support regional transparency depending on the depth-order of layers, while double-reversing ones show no significant effects on both lightness perception phenomena. At the same time, the joint-factor representation map for haze illusion suggests the corresponding perceptual transparency region.
CONCLUSIONS: The haze illusion in synergy with perceptual transparency is more complex than the single X-junction-based transparency perception analyses. It is found that the haze illusion is accompanied by the perceptual transparency which acts on certain effect on the formation and transformation of apparent haze. As the key configuration of perceptual organization, X-junctions play an important role in linking both lightness perception phenomena with mutual influence and distinction between each other.