A 360° Omnidirectional Photometer using a Ricoh Theta Z1

Color and Imaging Conference (CIC30) 2022


Spot photometers measure the luminance that is emitted or reflected from a small surface area in a physical environment. Because the measurement is limited to a “spot,” capturing dense luminance readings for an entire environment is impractical. In this project, preliminary results are provided which demonstrate the potential of using an off-the-shelf commercial camera to operate as a 360° luminance meter. The method uses the Ricoh Theta Z1 camera, which provides a full 360° omnidirectional field of view and an API to access the camera’s minimally processed RAW images. Working from the RAW images, a calibration method is described to map the RAW images under different exposures and ISO settings to luminance values. By combining the calibrated sensor with multi-exposure high-dynamic-range imaging, a cost-effective mechanism to capture dense luminance maps of environments is provided. Early results show that using the Ricoh Theta as a luminance meter performs well when validated against a significantly more expensive spot photometer.

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