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Jan J. Koenderink, Andrea J. van Doorn, Astrid M. L. Kappers, Sylvia C. Pont, James T. Todd; The perception of light fields in empty space. Journal of Vision 2005;5(8):558. doi: 10.1167/5.8.558.
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© ARVO (1962-2015); The Authors (2016-present)
Question: The “Light Field” denotes the radiance as a function of position and direction in space. It generally varies from point to point. The light field is implied by the appearances of objects in a scene, since radiation itself remains invisible. Do human observers “perceive” the light field in the empty space between objects?
Rationale: The “perception” of the light field at a location in empty space can be operationalized as the expectation of what a test body would look like when introduced at that location. Expectations can be “measured” via answers to questions that depend upon the existence of such expectations.
Method: A physical scene was set up and stereophotographs were made under a variety of illumination conditions. Photographs were presented stereoscopically and an illuminated spherical gauge figure was introduced at various locations in the scene. Observers were free to adjust intensity, direction and diffuseness of the light field used for rendering the gauge figure. Their criterion was the “fit” of the illuminated gauge figure in the scene. This allows us to quickly “probe” the perceived light field at various locations in the perceived scene.
Result: Observers do perceive at least the intensity, direction and diffuseness of light field throughout the scene with remarkable veridicality. A marked exception is the fact that observers completely fail to perceive the volume-shadows of objects.
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