Colour expectations across illumination changes
Colour expectations across illumination changes
This study investigates human expectations towards naturalistic colour changes under varying illuminations. Understanding colour expectations is key to both scientific research on colour constancy and applications of colour and lighting in art and industry. We reanalysed data from asymmetric colour matches of a previous study and found that colour adjustments tended to align with illuminant-induced colour shifts predicted by naturalistic, rather than artificial, illuminants and reflectances. We conducted three experiments using hyperspectral images of naturalistic scenes to test if participants judged colour changes based on naturalistic illuminant and reflectance spectra as more plausible than artificial ones, which contradicted their expectations. When we consistently manipulated the illuminant (Experiment 1) and reflectance (Experiment 2) spectra across the whole scene, observers chose the naturalistic renderings significantly above the chance level (>25 %) but barely more often than any of the three artificial ones, collectively (>50 %). However, when we manipulated only one object/ area’s reflectance (Experiment 3), observers more reliably identified the version in which the object had a naturalistic reflectance like the rest of the scene. Results from Experiments 2–3 and additional analyses suggested that relational colour constancy strongly contributed to observer expectations, and stable cone-excitation ratios are not limited to naturalistic illuminants and reflectances but also occur for our artificial renderings. Our findings indicate that relational colour constancy and prior knowledge about surface colour shifts help to disambiguate surface colour identity under illumination changes, enabling human observers to recognise surface colours reliably in naturalistic conditions. Additionally, relational colour constancy may even be effective in many artificial conditions.
Colour constancy, Colour rendering, Hyperspectral images, Lighting, Natural scenes
Karimipour, Hamed
f712f196-cee9-4f9f-bd4e-1621200d5979
Witzel, Christoph
dfb994f1-7007-441a-9e1a-ddb167f44166
September 2024
Karimipour, Hamed
f712f196-cee9-4f9f-bd4e-1621200d5979
Witzel, Christoph
dfb994f1-7007-441a-9e1a-ddb167f44166
Karimipour, Hamed and Witzel, Christoph
(2024)
Colour expectations across illumination changes.
Vision Research, 222, [108451].
(doi:10.1016/j.visres.2024.108451).
Abstract
This study investigates human expectations towards naturalistic colour changes under varying illuminations. Understanding colour expectations is key to both scientific research on colour constancy and applications of colour and lighting in art and industry. We reanalysed data from asymmetric colour matches of a previous study and found that colour adjustments tended to align with illuminant-induced colour shifts predicted by naturalistic, rather than artificial, illuminants and reflectances. We conducted three experiments using hyperspectral images of naturalistic scenes to test if participants judged colour changes based on naturalistic illuminant and reflectance spectra as more plausible than artificial ones, which contradicted their expectations. When we consistently manipulated the illuminant (Experiment 1) and reflectance (Experiment 2) spectra across the whole scene, observers chose the naturalistic renderings significantly above the chance level (>25 %) but barely more often than any of the three artificial ones, collectively (>50 %). However, when we manipulated only one object/ area’s reflectance (Experiment 3), observers more reliably identified the version in which the object had a naturalistic reflectance like the rest of the scene. Results from Experiments 2–3 and additional analyses suggested that relational colour constancy strongly contributed to observer expectations, and stable cone-excitation ratios are not limited to naturalistic illuminants and reflectances but also occur for our artificial renderings. Our findings indicate that relational colour constancy and prior knowledge about surface colour shifts help to disambiguate surface colour identity under illumination changes, enabling human observers to recognise surface colours reliably in naturalistic conditions. Additionally, relational colour constancy may even be effective in many artificial conditions.
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Accepted/In Press date: 19 June 2024
e-pub ahead of print date: 3 July 2024
Published date: September 2024
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Publisher Copyright:
© 2024 The Authors
Keywords:
Colour constancy, Colour rendering, Hyperspectral images, Lighting, Natural scenes
Identifiers
Local EPrints ID: 492161
URI: http://eprints.soton.ac.uk/id/eprint/492161
ISSN: 0042-6989
PURE UUID: 6d3f05b3-2a5b-4d42-a4b5-b357dd4067e3
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Date deposited: 18 Jul 2024 16:45
Last modified: 30 Jul 2024 01:58
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Author:
Hamed Karimipour
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