Per-pixel radiometric calibration to silux

In 2023, Richards and Hübner proposed silux as a new standard unit of irradiance for the full 350-1100 [nm] band, specifically addressing the mismatch between the photopic response of the human eye and spectral sensitivity of new low-light, Silicon, CMOS sensors with enhanced NIR response. This spectral mismatch between the response of the human eye and the spectral sensitivity of the sensor can lead to significant errors in measuring the magnitude of the signal available to a different camera system with the traditional lux unit. In this correspondence, we demonstrate a per-pixel calibration of a camera to create the first imaging siluxmeter. To do this, we developed a comprehensive per-pixel model as well as the experimental and data reduction methods to estimate the parameters. These parameters are then combined to an updated NVIPM measured system component that now provides the conversion factor from device units of DN to silux, lux, and other radiometric units. Additionally, the accuracy of the measurements and modeling are assessed through comparisons to field observations and validating/transferring calibration from one low light camera to another. Following this process, other low-light cameras can be calibrated and applied to scenes such that they may be accurately characterized using silux as the standard unit.