Purchase this article with an account.
Alessandro Soranzo, Carlo Fantoni; Semi-transparent layers enhance the simultaneous lightness contrast. Journal of Vision 2005;5(8):564. doi: 10.1167/5.8.564.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Helmholtz (1866) reported that the redness of a gray target on a red background was enhanced by covering it with a Semi Transparent Layer (S-TL).
We observed a similar effect in the achromatic domain: when a S-TL is superposed on the classic simultaneous lightness contrast display in order to cover both the targets, the lightness difference between the targets enhances compared to the condition without the S-TL. We explored this phenomenon in a CRT experiment using a simultaneous lightness contrast display with a mid gray (corresponding to 6 Munsell units) targets and S-TLs (transmittance = 50%) with different sizes and simulated reflectances. The relative size of the S-TL was varied amongst 5 levels: 1.3, 1, 0.74, 0.5 and 0.3 times the area of the black and white backgrounds. Two levels of the simulated reflectance of the S-TL were used: corresponding to 4 and 8 Munsell units. Observers were asked to select, from a Munsell scale, two patches: one matching the lightness of the target standing on the white background and the other matching the lightness of the target standing on the black background. Results showed that the lightness difference between the targets was enhanced, with respect to the condition without the S-TL, when the relative size of the S-TL was equal to 0.74, 0.5 and 0.3, while the lightness difference was reduced when the relative size was 1.3 and 1. Furthermore, the enhancement of the lightness difference increased as the simulated reflectance of the S-TL decreased. According to Soranzo and Agostini (in press) we suggest that these results could be explained by the relation among the luminance ratios between the Contextual edge (the edge in the surrounding area) and the Mediating edge (the edge in the enclosed area).
This PDF is available to Subscribers Only