Prototypes

Practical Multispectral Lighting Reproduction

2016 - Present
Project Leader: Chloe LeGrande

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We present a practical framework for reproducing omnidirectional incident illumination conditions with complex spectra using an LED sphere with multispectral LEDs. For lighting acquisition, we augment standard RGB panoramic photography with one or more observations of a color chart. We solve for how to drive the LEDs in each light source to match the observed RGB color of the environment and to best approximate the spectral lighting properties of the scene illuminant. Even when solving for non-negative intensities, we show that accurate illumination matches can be achieved with as few as four or six LED spectra for the entire ColorChecker chart for a wide gamut of incident illumination spectra.

A significant benefit of our approach is that it does not require the use of specialized equipment (other than the LED sphere) such as monochromators, spectroradiometers, or explicit knowledge of the LED power spectra, camera spectral response curves, or color chart reflectance spectra. We describe two useful and easy to construct devices for multispectral illumination capture, one for slow measurements of detailed angular spectral detail, and one for fast measurements with coarse spectral detail.

We validate the approach by realistically compositing real subjects into acquired lighting environments, showing accurate matches to how the subject would actually look within the environments, even for environments with mixed illumination sources, and demonstrate real-time lighting capture and playback using the technique.