City of lights – city of lighting: Luminance and heterochromatic brightness

Just about a century ago, luminance was established by the C.I.E. as the standard measure of light intensity. I will trace its historic origins in Paris at the turn of the 20th century, the great successes of luminance in standardizing lighting, and its shortcomings in adequately capturing heterochromatic brightness.

This presentation explores advances in modeling heterochromatic brightness, leveraging psychophysical tasks, neural correlates, and real-world lighting experiments. Central to this work is a robust ranking task in which observers evaluated the brightness of diverse color patches. The task reliably captured heterochromatic brightness judgments, revealing that a non-linear model, based on the maximum value of three weighted primaries (MaxRGB), consistently outperformed traditional metrics such as luminance, radiance, and CIE-derived color appearance models.

These findings align with results from steady-state visual evoked potential (SSVEP) experiments, which highlight distinct neural responses to luminance and heterochromatic brightness at different temporal frequencies. Further validation comes from experiments with tunable LED lamps, confirming the model's relevance across real-world lighting conditions. The results also include large-scale online data collection, demonstrating that brightness rankings remain robust even under less controlled environments.

These findings not only refine our understanding of brightness perception but also advocate for models better aligned with human visual experiences, echoing the innovative spirit of Paris’s historic contributions to vision science.

The Cognitive Science Colloquium series is the most attended event of our department, hosting monthly talks by world-renowned experts in various fields of cognitive science, including neuroscience, psychology, linguistics, philosophy and anthropology.

2024-2025 Program