Chromatic and spatial processing is tightly linked in the visual system. The S-cone system is generally poor at resolving fine spatial detail due to the paucity of S cones in the retina. The other two pathways, the chromatic (red-green) and achromatic (luminance) channel, both of which receive input from the L and M cones, also exhibit different spatial characteristics due to post-receptoral spatial processing. The spatio-chromatic properties of these channels have been studied extensively in detection and discrimination tasks [1-6] but much less is known how the different spatial characteristics affect the appearance and how the different channels interact at different spatial scales.
The importance of understanding and modelling spatial interactions between chromatic and luminance channels is easily demonstrated in the figure below: only when the luminance plane is blurred, do we see a loss of sharpness and also slight changes in colour appearance.
As a consequence of these spatio-chromatic interactions, appearance models based on the perception of spatially uniform colour patches are not able to predict the appearance of complex spatio-chromatic images. This is likely a contributing factor to the fact that none of the current spatio-chromatic appearance models for high dynamic range (HDR) have achieved the same status and level of universality as uniform colour patch CAMs (e.g. CIECAM02).
The aim of our new project is to create a spatio-chromatic model of colour vision, capable of robust predictions across the luminance range from 0.02 to 10000 cd/m2. One of our applications will consist of developing a retargeting model for different age groups by taking into account the age-related changes in the optics of the eye and age-related changes in post-receptoral processing. Updates, data and code are available on https://www.cl.cam.ac.uk/research/rainbow/projects/hdr-csf/
Dr. R Mantiuk, Computer Science, University of Cambridge
Dr J Martinovic, Psychology, University of Aberdeen
Prof. G Finlayson, Computer Science, University of East Anglia
 Wuerger, S.M. and Morgan, M.J. (1999). The input of the long- and medium-wavelength-sensitive cones to orientation discrimination. Journal of the Optical Society of America A, 16(3), 443-454.
 Wuerger, S.M., Morgan M.J., Westland, S., and Owens, H. (2000). The spatio-chromatic sensitivity of the human visual system. New Journal of Physics: Physiological Measurements, 21(11), 505-513.
 Wuerger, S.M., Owens, H, and Westland, S. (2001). Blur Tolerance for luminance and chromatic stimuli. Journal of the Optical Society of America A, 18(6), 1231-1239.
 Wuerger, S.M., Watson, A.B., and Ahumada, A. (2002). Towards a spatio-chromatic standard observer for detection, in Human Vision and Electronic Imaging VII, ed. B. E. Rogowitz and T.N. Pappas, Proceedings of SPIE, San Jose, CA, USA, Vol. 4662, pp. 159-172.
 Martinovic, Mordal, Wuerger (2011). Event-related potentials reveal an early advantage for luminance contours in the processing of objects, Journal of Vision, 11(7), p. 1-15.
 Kosilo, M., Wuerger, S. M., Craddock, M., Jennings, B. J., Hunt, A. R., & Martinovic, J. (2013). Low-level and high-level modulations of fixational saccades and high frequency oscillatory brain activity in a visual object classification task. Frontiers in Psychology, 4.
 Sophie Wuerger, Maliha Ashraf, Minjung Kim, Jasna Martinovic, María Pérez-Ortiz, Rafał K. Mantiuk; Spatio-chromatic contrast sensitivity under mesopic and photopic light levels. Journal of Vision 2020; 20(4):23. doi: https://doi.org/10.1167/jov.20.4.23
Acknowledgement of Support
EPSRC EP/P007503/1 (2017-2021)