David Brainard

David-Brainard.jpg

David Brainard is interested in human vision, machine vision, and computational modelling of visual processing. His primary research is concerned with how the visual system estimates object properties from the information available in the light signal incident at the eye. To study this general problem, He conducts psychophysical experiments to investigate questions such as how object colour appearance is related to object surface properties under a wide range of illumination conditions and how colour is used to identify objects. He also formulates computational models of visual processing. In addition, David is interested in developing machine visual systems that can mimic human performance and in understanding the neural mechanisms of vision.

Colour Group 2006: Understanding the Appearance of Spot Colors

Observers use a wide range of color names, including white, to describe monochromatic flashes with a retinal size comparable to that of a single cone. We model such data as a consequence of information loss arising from trichromatic sampling. The model starts with the simulated responses of the individual L, M, and S cones actually present in the cone mosaic and uses these to reconstruct the L-, M-, and S-cone signals that were present at every image location. We incorporate the optics and the mosaic topography of individual observers, as well as the spatio-chromatic statistics of natural images. We simulated the experiment of H. Hofer, B. Singer, & D. R. Williams (2005) and predicted the color name on each simulated trial from the average chromaticity of the spot reconstructed by our model. Broad features of the data across observers emerged naturally as a consequence of the measured individual variation in the relative numbers of L, M, and S cones. The model's output is also consistent with the appearance of larger spots and of sinusoidal contrast modulations. Finally, the model makes testable predictions for future experiments that study how color naming varies with the fine structure of the retinal mosaic.

This work is published as: Brainard, D. H., Williams, D. R., & Hofer, H. (2008). Trichromatic reconstruction from the interleaved cone mosaic: Bayesian model and the color appearance of small spots. Journal of Vision, 8(5):15, 1-23, http://journalofvision.org/8/5/15/, doi:10.1167/8.5.15.

 

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