Active manipulation of surface orientation under directional illumination improves color discrimination

Abstract

Two surfaces that appear different colors under one illumination might appear the same color under another illumination. This phenomenon is known as illuminant metamerism and is thought to limit surface color discrimination. However, real-world lighting environments are not directionally uniform. In theory, surfaces that appear the same color at one tilt might not appear the same color at another tilt where they sample a different illumination spectrum. We tested whether human observers could use this directional variation to improve surface color discrimination. Our results confirm that human color discrimination is improved when observers are able to tilt surfaces to sample directional lighting. Observer sampling motions were spatiotemporally structured and appeared to be directed towards the general lighting geometry rather than systematically maximizing color discriminating information for specific surface pairs.

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BibTeX RIS

BibTeX

@misc{mohiddin2026active,
  title = {{Active manipulation of surface orientation under directional illumination improves color discrimination}},
  author = {S. N. Mohiddin and T. Morimoto and F. Coupette and H. E. Smithson},
  howpublished = {bioRxiv},
  year = {2026},
  month = nov,
  doi = {10.64898/2026.11.03.763965},
  url = {https://www.biorxiv.org/content/10.64898/2026.11.03.763965v1},
  note = {CC BY},
}

RIS

TY  - UNPB
TI  - Active manipulation of surface orientation under directional illumination improves color discrimination
AU  - S. N. Mohiddin
AU  - T. Morimoto
AU  - F. Coupette
AU  - H. E. Smithson
PY  - 2026
DA  - 2026/11/03
PB  - bioRxiv
DO  - 10.64898/2026.11.03.763965
UR  - https://www.biorxiv.org/content/10.64898/2026.11.03.763965v1
AB  - Two surfaces that appear different colors under one illumination might appear the same color under another illumination. This phenomenon is known as illuminant metamerism and is thought to limit surface color discrimination. However, real-world lighting environments are not directionally uniform. In theory, surfaces that appear the same color at one tilt might not appear the same color at another tilt where they sample a different illumination spectrum. We tested whether human observers could use this directional variation to improve surface color discrimination. Our results confirm that human color discrimination is improved when observers are able to tilt surfaces to sample directional lighting. Observer sampling motions were spatiotemporally structured and appeared to be directed towards the general lighting geometry rather than systematically maximizing color discriminating information for specific surface pairs.
ER  -

Abstract

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