{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T01:23:59Z","timestamp":1777339439597,"version":"3.51.4"},"reference-count":26,"publisher":"Public Library of Science (PLoS)","issue":"3","license":[{"start":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T00:00:00Z","timestamp":1773360000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002241","name":"Japan Science and Technology Agency","doi-asserted-by":"publisher","award":["SPRING Grant Number JPMJSP2180"],"award-info":[{"award-number":["SPRING Grant Number JPMJSP2180"]}],"id":[{"id":"10.13039\/501100002241","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"publisher","award":["KAKENHI Grant Number 23K28174"],"award-info":[{"award-number":["KAKENHI Grant Number 23K28174"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001691","name":"Japan Society for the Promotion of Science","doi-asserted-by":"publisher","award":["KAKENHI Grant Number 21KK0203"],"award-info":[{"award-number":["KAKENHI Grant Number 21KK0203"]}],"id":[{"id":"10.13039\/501100001691","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:p>Luminosity thresholds define the luminance boundary at which a surface color shifts in appearance from being perceived as an illuminated surface to appearing self-luminous. Previous research suggests that the human visual system infers these thresholds based on internal references of physically realizable surface colors under a given illumination, referred to as the physical gamut. A surface is perceived as self-luminous when its luminance exceeds the upper limit of this empirically internalized gamut. However, the precise structure and boundaries of these gamuts remain uncertain. Optimal colors, which represent theoretical surface reflectances under specific illuminants, have been shown to provide an effective model for visualizing and computing the physical gamuts. In prior studies, optimal colors have successfully predicted luminosity thresholds; however, these findings were limited to highly simplified, abstract stimuli. Whether this framework generalizes to more naturalistic viewing conditions has remained an open question. In the present study, we demonstrate that the theory of an internal reference in the form of an empirically constructed physical gamut, visualized through optimal colors, remains valid under more natural conditions. Our results confirm that optimal colors can still accurately predict luminosity thresholds in such settings. Moreover, our findings suggest that the luminosity thresholds encompass both self-luminosity and naturalness concepts. Consequently, this may imply that the notion of physical gamut could encompass both concepts as well and could be defined as \u201call physically possible colors in a scene for an object that does not emit light.\u201d These insights have profound potential implications for applied fields (e.g., XR or projection mapping). For example, they provide a theoretical framework that specifies the luminance and color boundaries virtual objects should not exceed to remain realistically integrated into AR\/MR scenes. In fundamental science, these findings can improve our understanding of the perception of naturalness in images.<\/jats:p>","DOI":"10.1371\/journal.pone.0343984","type":"journal-article","created":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T17:48:11Z","timestamp":1773424091000},"page":"e0343984","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":1,"title":["Optimal colors can predict luminosity thresholds in natural scenes"],"prefix":"10.1371","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0009-0009-4526-8063","authenticated-orcid":true,"given":"Killian","family":"Duay","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Takehiro","family":"Nagai","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"340","published-online":{"date-parts":[[2026,3,13]]},"reference":[{"key":"pone.0343984.ref001","doi-asserted-by":"crossref","DOI":"10.4324\/9781315009285","volume-title":"The world of colour","author":"D Katz","year":"2013"},{"issue":"13","key":"pone.0343984.ref002","first-page":"3","article-title":"Luminosity thresholds of colored surfaces are determined by their upper-limit luminances empirically internalized in the visual system.","volume":"21","author":"T Morimoto","year":"2021"},{"issue":"11","key":"pone.0343984.ref003","doi-asserted-by":"crossref","first-page":"1049","DOI":"10.1364\/JOSA.49.001049","article-title":"Fluorescence and Gray Content of Surface Colors","volume":"49","author":"RM Evans","year":"1959","journal-title":"J Opt Soc Am"},{"issue":"11","key":"pone.0343984.ref004","doi-asserted-by":"crossref","first-page":"1319","DOI":"10.1364\/JOSA.57.001319","article-title":"Chromatic strength of colors: dominant wavelength and purity","volume":"57","author":"RM Evans","year":"1967","journal-title":"J Opt Soc Am"},{"issue":"4","key":"pone.0343984.ref005","doi-asserted-by":"crossref","first-page":"580","DOI":"10.1364\/JOSA.58.000580","article-title":"Chromatic strengths of colors. II. The Munsell system","volume":"58","author":"RM Evans","year":"1968","journal-title":"J Opt Soc Am"},{"issue":"5","key":"pone.0343984.ref006","doi-asserted-by":"crossref","first-page":"628","DOI":"10.1364\/JOSA.59.000628","article-title":"Chromatic strength of colors. 3. Chromatic surrounds and discussion","volume":"59","author":"RM Evans","year":"1969","journal-title":"J Opt Soc Am"},{"issue":"4","key":"pone.0343984.ref007","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1007\/BF00344165","article-title":"On visual detection of light sources","volume":"21","author":"S Ullman","year":"1976","journal-title":"Biol Cybern"},{"issue":"9","key":"pone.0343984.ref008","doi-asserted-by":"crossref","first-page":"991","DOI":"10.1068\/p230991","article-title":"The perception of luminosity on different backgrounds and in different illuminations","volume":"23","author":"F Bonato","year":"1994","journal-title":"Perception"},{"issue":"3","key":"pone.0343984.ref009","doi-asserted-by":"crossref","first-page":"436","DOI":"10.1364\/JOSAA.13.000436","article-title":"Luminosity thresholds: effects of test chromaticity and ambient illumination","volume":"13","author":"JM Speigle","year":"1996","journal-title":"J Opt Soc Am A Opt Image Sci Vis"},{"issue":"4","key":"pone.0343984.ref010","doi-asserted-by":"crossref","first-page":"737","DOI":"10.1364\/JOSAA.18.000737","article-title":"Brightness, not luminance, determines transition from the surface-color to the aperture-color mode for colored lights","volume":"18","author":"K Uchikawa","year":"2001","journal-title":"J Opt Soc Am A"},{"issue":"11","key":"pone.0343984.ref011","doi-asserted-by":"crossref","first-page":"361","DOI":"10.1364\/JOSA.25.000361","article-title":"Maximum Visual Efficiency of Colored Materials","volume":"25","author":"DL MacAdam","year":"1935","journal-title":"J Opt Soc Am"},{"issue":"8","key":"pone.0343984.ref012","doi-asserted-by":"crossref","first-page":"249","DOI":"10.1364\/JOSA.25.000249","article-title":"The Theory of the Maximum Visual Efficiency of Colored Materials","volume":"25","author":"DL MacAdam","year":"1935","journal-title":"J Opt Soc Am"},{"issue":"2","key":"pone.0343984.ref013","doi-asserted-by":"crossref","DOI":"10.1364\/JOSAA.29.00A133","article-title":"Estimating illuminant color based on luminance balance of surfaces","volume":"29","author":"K Uchikawa","year":"2012","journal-title":"J Opt Soc Am A Opt Image Sci Vis"},{"issue":"4","key":"pone.0343984.ref014","doi-asserted-by":"crossref","DOI":"10.1364\/JOSAA.31.00A239","article-title":"Color constancy in a scene with bright colors that do not have a fully natural surface appearance","volume":"31","author":"K Fukuda","year":"2014","journal-title":"J Opt Soc Am A Opt Image Sci Vis"},{"issue":"3","key":"pone.0343984.ref015","doi-asserted-by":"crossref","DOI":"10.1364\/JOSAA.33.00A214","article-title":"Effects of surrounding stimulus properties on color constancy based on luminance balance","volume":"33","author":"T Morimoto","year":"2016","journal-title":"J Opt Soc Am A Opt Image Sci Vis"},{"issue":"3","key":"pone.0343984.ref016","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1167\/jov.21.3.7","article-title":"Human color constancy based on the geometry of color distributions","volume":"21","author":"T Morimoto","year":"2021","journal-title":"J Vis"},{"issue":"8","key":"pone.0343984.ref017","doi-asserted-by":"crossref","first-page":"4","DOI":"10.1167\/15.8.4","article-title":"Effect of material perception on mode of color appearance","volume":"15","author":"I Kuriki","year":"2015","journal-title":"J Vis"},{"issue":"8","key":"pone.0343984.ref018","doi-asserted-by":"crossref","first-page":"1622","DOI":"10.1364\/JOSAA.13.001622","article-title":"Limitations of surface-color and apparent-color constancy","volume":"13","author":"I Kuriki","year":"1996","journal-title":"J Opt Soc Am A Opt Image Sci Vis"},{"key":"pone.0343984.ref019","volume-title":"Color science: concepts and methods, quantitative data and formulae","author":"G Wyszecki","year":"2000"},{"issue":"1967","key":"pone.0343984.ref020","first-page":"20212483","article-title":"Colour constancy failures expected in colourful environments","volume":"289","author":"DH Foster","year":"2022","journal-title":"Proc Biol Sci"},{"key":"pone.0343984.ref021","author":"D Foster","year":"2022"},{"issue":"10","key":"pone.0343984.ref022","doi-asserted-by":"crossref","first-page":"2359","DOI":"10.1364\/JOSAA.23.002359","article-title":"Frequency of metamerism in natural scenes","volume":"23","author":"DH Foster","year":"2006","journal-title":"J Opt Soc Am A Opt Image Sci Vis"},{"issue":"1","key":"pone.0343984.ref023","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1002\/col.5080140107","article-title":"Calibration of a computer controlled color monitor","volume":"14","author":"DH Brainard","year":"1989","journal-title":"Color Research & Application"},{"key":"pone.0343984.ref024","first-page":"2","article-title":"Display characterization","volume":"80","author":"DH Brainard","year":"2002","journal-title":"Signal Process"},{"issue":"397","key":"pone.0343984.ref025","first-page":"198","article-title":"Better Bootstrap Confidence Intervals: Rejoinder","volume":"82","author":"B Efron","year":"1987","journal-title":"Journal of the American Statistical Association"},{"issue":"2031","key":"pone.0343984.ref026","first-page":"20240909","article-title":"Effects of visual diet on colour discrimination and preference","volume":"291","author":"AE Skelton","year":"2024","journal-title":"Proc Biol Sci"}],"container-title":["PLOS One"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0343984","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T17:48:16Z","timestamp":1773424096000},"score":1,"resource":{"primary":{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0343984"}},"subtitle":[],"editor":[{"given":"Stephen D.","family":"Ginsberg","sequence":"first","affiliation":[],"role":[{"role":"editor","vocabulary":"crossref"}]}],"short-title":[],"issued":{"date-parts":[[2026,3,13]]},"references-count":26,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2026,3,13]]}},"URL":"https:\/\/doi.org\/10.1371\/journal.pone.0343984","relation":{},"ISSN":["1932-6203"],"issn-type":[{"value":"1932-6203","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,3,13]]}}}