High-resolution time series of the dark outputs (top) and their difference (bottom) for two different wavelength bins offering different qualities of combination, leading to different mean leakage and correlation levels. Correlation within each pair is the effect leading to self calibration in the differential output. Correlation between spectral channels is what motivates the data whitening approach. The time series shown here are only indicative, because in practice integrations are made over longer times and are contaminated by sensor noises before they can be numerically subtracted.