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Copyright and Use of This Thesis This Thesis Must Be Used in Accordance with the Provisions of the Copyright Act 1968 COPYRIGHT AND USE OF THIS THESIS This thesis must be used in accordance with the provisions of the Copyright Act 1968. Reproduction of material protected by copyright may be an infringement of copyright and copyright owners may be entitled to take legal action against persons who infringe their copyright. Section 51 (2) of the Copyright Act permits an authorized officer of a university library or archives to provide a copy (by communication or otherwise) of an unpublished thesis kept in the library or archives, to a person who satisfies the authorized officer that he or she requires the reproduction for the purposes of research or study. The Copyright Act grants the creator of a work a number of moral rights, specifically the right of attribution, the right against false attribution and the right of integrity. You may infringe the author’s moral rights if you: - fail to acknowledge the author of this thesis if you quote sections from the work - attribute this thesis to another author - subject this thesis to derogatory treatment which may prejudice the author’s reputation For further information contact the University’s Copyright Service. sydney.edu.au/copyright The Computation of Surface Lightness in Simple and Complex Scenes Alexandra C. Schmid School of Psychology The University of Sydney A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) 2016 Declaration of Originality This thesis is submitted to the University of Sydney in fulfilment of the requirements for the Degree of Doctor of Philosophy. The work presented in this thesis is, to the best of my knowledge and belief, original except as acknowledged in the text. I hereby declare that I have not submitted this material, either in full or in part, for a degree at this or any other institution. Alexandra C. Schmid SYDNEY, October 2015 Abstract The present thesis examined how reflectance properties and the complexity of surface mesostructure (small-scale surface relief) influence perceived lightness in centre- surround displays. Chapters 2 and 3 evaluated the role of surface relief, gloss, and interreflections on lightness constancy, which was examined across changes in background albedo and illumination level. For surfaces with visible mesostructure (“rocky” surfaces), lightness constancy across changes in background albedo was better for targets embedded in glossy versus matte surfaces. However, this improved lightness constancy for gloss was not observed when illumination varied. Control experiments compared the matte and glossy rocky surrounds to two control displays, which matched either pixel histograms or a phase-scrambled power spectrum. Lightness constancy was improved for rocky glossy displays over the histogram-matched displays, but not compared to phase-scrambled variants of these images with equated power spectrums. The results were similar for surfaces rendered with 1, 2, 3 and 4 interreflections. These results suggest that lightness perception in complex centre-surround displays can be explained by the distribution of contrast across space and scale, independently of explicit information about surface shading or specularity. The results for surfaces without surface relief (“homogeneous” surfaces) differed qualitatively to rocky surfaces, exhibiting abrupt steps in perceived lightness at points at which the targets transitioned from being increments to decrements. Chapter 4 examined whether homogeneous displays evoke more complex mid-level representations similar to conditions of transparency. Matching target lightness in a homogeneous display to that in a textured or rocky display required varying both lightness and transmittance of the test patch on the textured display to obtain the most satisfactory matches. However, transmittance was only varied to match the contrast of targets against homogeneous surrounds, and not to explicitly match the amount of transparency perceived in the displays. The results suggest perceived target-surround edge contrast differs between homogeneous and textured displays. Varying the mid-level property of transparency in textured displays provides a natural means for equating both target lightness and the unique appearance of the edge contrast in homogeneous displays. i Acknowledgements First and foremost I would like to thank my supervisor Professor Bart Anderson for his guidance and support throughout my PhD candidature. I have been lucky to have a supervisor who responds to emails almost instantaneously at any time of day, and provides exceptionally quick feedback on chapter drafts. I would also like to thank Bart for inspiring me to become a better thinker and writer, and giving me the opportunity to learn many valuable skills working as an RA in the years leading up to my PhD. Above all, you have imparted your extensive knowledge and passion for the field of material perception, which I hope to carry into my future research career. Thank you to past and present members of the Anderson lab for creating a great working environment. I would particularly like to thank the post-docs in the lab Phil Marlow and Juno Kim for helping me whenever I was stuck with a programming problem. Thank you Kai for being one of the few people I could talk to about the lightness literature, and whiz kid Scott for learning to program Blender in his first week of honours, and inadvertently motivating me to do the same. Thank you Siva for your company in the lab towards the end. I would like to thank my family and friends, especially my parents Rennie and Robyn for their constant encouragement and support of my educational pursuits. You have taught me that as long as I try hard I can achieve anything I put my mind to. Thank you Danielle for being a great and supportive friend, and willing research participant. Finally, I would like to express my love and gratitude to my partner Marios for going through both my honours and PhD theses with me, while simultaneously finishing his own PhD thesis. Your integrity as a researcher and constant enthusiasm for learning is an inspiration to myself and others. ii List of Publications Peer-Reviewed Articles Schmid, A. C., & Anderson, B. L. (2014). Do surface reflectance properties and 3-D mesostructure influence the perception of lightness? Journal of Vision, 14(8):24, 1-24. Oral Presentations Schmid, A. S., & Anderson, B. L. (2015). Surface lightness in complex centre- surround displays: The important role of interreflections. 42nd Australasian Experimental Psychology Conference (EPC), Sydney, NSW, Australia. Schmid, A. S., & Anderson, B. L. (2014). How does the brain represent surface lightness for simple versus complex centre-surround displays? 41st Australasian Experimental Psychology Conference (EPC), Brisbane, QLD, Australia. Schmid, A. S., & Anderson, B. L. (2013). How does the brain represent surface lightness? Psychology Postgraduate Conference, Sydney, NSW, Australia. Schmid, A. S., & Anderson, B. L. (2013). Lightness perception in scenes that are 3D and naturalistic versus 2D and impoverished. University of Sydney Faculty Heats for the Three Minute Thesis Competition (3MT), Sydney, NSW, Australia. Schmid, A. S., & Anderson, B. L. (2013). We are living in a material world: Lightness perception is more consistent in natural scenes that have real material properties such as rockiness and gloss. 1st Inaugural University of Sydney’s School of Psychology Day of Research (PsychFest), Sydney, NSW, Australia. Conference Proceedings Schmid, A. S., & Anderson, B. L. (2014). Linking low-level and mid-level accounts of lightness perception. 14th Annual Vision Sciences Society Conference (VSS), St. Pete Beach, FL, USA. iii Contents Abstract ....................................................................................................................................... i Acknowledgements .................................................................................................................... ii List of Publications .................................................................................................................... iii List of Figures ............................................................................................................................ vi List of Tables ........................................................................................................................... viii Chapter 1. Determining how the Visual System computes Surface Lightness in Complex Scenes .............................................................................................................................. 1 Classes of Lightness Theories ................................................................................................. 4 Brightness Models ........................................................................................................................... 5 Framework models ....................................................................................................................... 10 Decomposition models ................................................................................................................. 11 Relating Existing Lightness Theories to Real-World Scenes ................................................. 17 Potential Information about Lightness Available in Real-World Scenes ............................. 19 Shading, cast shadows and specular highlights ............................................................................ 19 Texture caused by complex mesostructure
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