Light and Spectra in the Wild - Spectral Structures of Light Fields: Measurement, Simulation and Visualisation

The study of the light field has become a valuable framework for capturing and analysing the complex distribution of light in natural environments. The directional, spatial, temporal and spectral structure of light, collectively influence the optical information available to an observer and thus impact our perception of the surrounding world. The extended definition of the light field, which is equivalent to the plenoptic function in perceptual studies, incorporates radiance as a function of spectral energy, position, direction, and time in space, quantifying all the optical information available to an observer. However, there is a considerable gap in measuring, describing, and visualizing the properties of the light field in the chromatic domain, which this thesis aimed to address. The thesis focuses on the research question of how to effectively describe, measure, simulate, and visualize the spatiotemporal dynamics of the spectral structure of light fields. To address this research question, We outlined four main objectives in the thesis, which are addressed in separate chapters. The first objective is to investigate the interplay between the colours of surfaces and light sources in 3D indoor scenes, and its effects on the spatial and angular distribution of light. The second objective was to quantify the directional and spatial variations of chromatic light field effects on correlated colour temperature and colour rendering. The third objective was to explore the objective measurement, description, and visualization of the 7D light-field properties of outdoor illumination. Finally, the fourth objective was to examine the relationship between image statistics and perceived time of day in Western European paintings from the 17th to 20th centuries to determine if the representation of lighting in paintings serves as a contextual cue for the time of day.