Copyright 2001 Society of Photo-Optical Instrumentation Engineers

This paper was published in the Proceedings of the SPIE Conference on Human Vision and Electronic Imaging (part of Electronic Imaging 2001, San Jose, CA) and is made available as an electronic reprint with permission of SPIE.  One print or electronic copy may be made for personal use only.  Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.