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Proceedings Paper

Deep shadows in a shallow box
Author(s): Xiang Huang; Ankit Mohan; Jack Tumblin
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Paper Abstract

We present a fast, low-cost technique to gather high-contrast 'relightable' photographs of desktop-sized objects. Instead of an elaborate light stage, we follow Mohan et al.; we place the object and a digitally steered spotlight inside a white cardboard box, aim the spotlight at the box interior, and move the spot to light the object from N repeatable lighting directions. However, strong ambient lighting from box interreflections causes 'shallow' shadows and reduces contrasts in all basis images. We show how to remove this ambient lighting computationally from the N images, by measuring an N ×N matrix of coupling factors between lighting directions using a mirrorsphere light probe. This linear method, suitable for any light stage, creates physically accurate 'deep shadow' basis images, yet imposes only a modest noise penalty, and does not require external light metering or illumination angle measurements. Results from our demonstration system support these claims.

Paper Details

Date Published: 12 February 2008
PDF: 9 pages
Proc. SPIE 6810, Computer Image Analysis in the Study of Art, 681003 (12 February 2008); doi: 10.1117/12.766949
Show Author Affiliations
Xiang Huang, Northwestern Univ. (United States)
Ankit Mohan, Northwestern Univ. (United States)
Jack Tumblin, Northwestern Univ. (United States)

Published in SPIE Proceedings Vol. 6810:
Computer Image Analysis in the Study of Art
David G. Stork; Jim Coddington, Editor(s)

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