The Color of Water: Using Underwater Photography to Estimate Water Quality

We describe a model for underwater illumination that is based on how light is absorbed and scattered by water, phytoplankton and other organic and inorganic matter in the water. To test the model, we built a color rig using a commercial point-and-shoot camera in an underwater housing and a calibrated color target. We used the measured spectral reflectance of the calibration color target and the measured spectral sensitivity of the camera to estimate the spectral power of the illuminant at the surface of the water. We then used this information, along with spectral basis functions describing light absorbance by water, phytoplankton, non-algal particles (NAP) and colored dissolved organic matter (CDOM), to estimate the spectral power of the illuminant and the amount of scattered light at each depth. Our results lead to insights about color correction, as well as the limitations of consumer digital cameras for monitoring water quality.