Upper panel: percentage of occupied pixels (distance to a filament smaller than 30 Mm) versus the number of PIL pixels. Each dot corresponds to a daily value. The solid line is a second degree polynomial fit on the 676 points. Lower panel: filament coverage (in ppm of the solar hemisphere) versus the number of occupied pixels (distance to a filament smaller than 30 Mm). The solid line is a second degree polynomial fit to the 676 points.