November 2002
Volume 2, Issue 7
Vision Sciences Society Annual Meeting Abstract  |   November 2002
Anomalous contours prevent brightness spreading in phantom illumination displays
Author Affiliations
  • Daniele Zavagno
    NEC Research Institute
Journal of Vision November 2002, Vol.2, 78. doi:
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      Daniele Zavagno; Anomalous contours prevent brightness spreading in phantom illumination displays. Journal of Vision 2002;2(7):78.

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      © ARVO (1962-2015); The Authors (2016-present)

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In the phantom illumination illusion a homogeneous dark background (B) shows two different brightness levels due to the presence of surfaces (S) shaded with a linear luminance gradient ranging from black to white. The spatial distribution of the shaded surfaces is so that all their light ends can be virtually connected with a contour. The portion of the background (B2) facing the light ends of S appears brighter than the rest of the background (B1).

Two experiments are discussed that show that when the distribution of S is so that B2 appears like an anomalous surface, then the brightness spreading that characterizes the illusion disappears. The first experiment was conducted on a CRT and the subject's task was to rate B2 with respect to B1 on a −20/+20 scale. The second experiment was conducted with paper displays using a paired comparison method with a forced choice task between which B2s appeared darker.

While the results strongly suggest that the brightness spreading is subsequent to figure-ground articulation, phenomenal observation of the experimental displays suggests also the presence of a low level component of the illusion which determines local effects for each S element. The formation of anomalous contours cannot overwhelm these local effects but it can prevent their spreading beyond S and its immediate surround (global effect).

The illusion is also discussed in relation to other brightness/lightness effects, such as color neon- spreading, assimilation and the glare effect.

Zavagno, D.(2002). Anomalous contours prevent brightness spreading in phantom illumination displays [Abstract]. Journal of Vision, 2( 7): 78, 78a,, doi:10.1167/2.7.78. [CrossRef]

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