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Lightness constancy: ratio invariance and luminance profile
The term simultaneous lightness constancy describes the capacity of the visual system to perceive equal reflecting
surfaces as having the same lightness despite lying in different illumination fields. In some cases, however, a
lightness constancy failure occurs; that is, equal reflecting surfaces appear different in lightness when differently illuminated. An open question is whether the luminance profile of the illumination edges affects simultaneous lightness constancy even when the ratio invariance property of the illumination edges is preserved. To explore this issue, we ran two experiments by using bipartite illumination displays. Both the luminance profile of an illumination edge and the luminance ratio amplitude between the illumination fields were manipulated. Results revealed that the simultaneous lightness constancy increases when the luminance profile of the illumination edge is gradual (rather than sharp) and homogeneous (rather than inhomogeneous), whereas it decreases when the luminance
ratio between the illumination fields is enlarged. The results are interpreted according to the layer decomposition
schema, stating that the visual system splits the luminance into perceived lightness and apparent illumination
components. We suggest that illumination edges having gradual and homogeneous luminance profiles facilitate
the luminance decomposition process, whereas wide luminance ratios impede it
Illumination control system
Experiment, testing effects of constant light intensity on Arabidopsis growth, utilizes wide-spectrum fluorescent lamps monitored by photocell which controls the power supplied to lamp
Donor binding energy and thermally activated persistent photoconductivity in high mobility (001) AlAs quantum wells
A doping series of AlAs (001) quantum wells with Si delta-modulation doping
on both sides reveals different dark and post-illumination saturation
densities, as well as temperature dependent photoconductivity. The lower dark
two-dimensional electron density saturation is explained assuming deep binding
energy of Delta_DK = 65.2 meV for Si-donors in the dark. Persistent
photoconductivity (PPC) is observed upon illumination, with higher saturation
density indicating shallow post-illumination donor binding energy. The
photoconductivity is thermally activated, with 4 K illumination requiring
post-illumination annealing to T = 30 K to saturate the PPC. Dark and
post-illumination doping efficiencies are reported.Comment: The values of binding energy changed from previous versions because
of a better understanding for the dielectric permittivity. Also, the Gamma -
X donor states are better explaine
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