Even after color calibration, we still require further color corrections when we edit, as seen in these before and after images. You can see how much red is missing in the top image. This is due to the shorter distance that red light travels through water. By doing the daily calibration, we have a calibrated starting point to compare and work from. Image courtesy of the NOAA Office of Ocean Exploration and Research, Discovering the Deep: Exploring Remote Pacific MPAs.