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C. S. Kallie, G. E. Legge, A. M. Y. Cheong, H. Park; Curved Objects May Enhance Visual Accessibility. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4114. doi: https://doi.org/.
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We define visual accessibility as the use of vision to travel efficiently and safely through an environment, to perceive the spatial layout of key features in the environment, and to keep track of one’s location in the layout. The detectability of objects is an important component of visual accessibility. Three important factors interact to determine detectability of objects - illumination, surface characteristics (such as color, contrast and reflectance), and 3D geometry (shape and size). The goal of this study was to examine how the detection of simple convex objects (boxes and cylinders) is influenced by color (gray and white) and lighting condition (overhead room illumination and side illumination from artificial windows). We predicted that white objects in front of a gray background will be more visible than gray objects - unless they are illuminated from the side. Side illumination will cause cylinders to be more visible than boxes (when boxes are positioned frontal-planar), even when cylinders are gray and boxes are white. The curved nature of cylinders provides additional contrast information, in the form of a luminance gradient, providing a basis for the prediction that cylinders are more detectable than (frontal-planar) boxes when illuminated from the side.
Eleven normally sighted college students made detection judgments yielding d’ for the presence or absence of real target objects in a real room. The subjects had simulated acuity reduction produced by blur glasses producing an average monocular acuity of 20/675. The rectangular boxes and curved cylinders had heights of 2, 4 and 6 ft, and were viewed from distances of 10, 17 and 24 ft. There were two lighting conditions: moderately uniform overhead room illumination, and an artificial window illuminating the subject and objects from the side.
Cylinders were more visible than boxes in overhead illumination and window illumination, but the difference was greater with window illumination. In most conditions, white objects were more visible than gray objects; however, gray cylinders were actually more visible than white boxes in artificial window illumination.
Curved surfaces provide reflectance gradients that are helpful in detectability from a wider range of viewpoints in the presence of directional illumination than objects with flat surfaces. This interaction of 3D geometry and illumination may significantly influence the detection of objects by individuals with low vision.
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