Filamentarity of 6568 structures as a function of filament surface measured by counting filament surface pixels n_S. The dashed blue line shows a model of the filamentarity in the case of a constant width of W = 2.53 pixels, and the red line shows the model for the broadening fit from Fig. 6. Formal numerical 3σ uncertainties from perimeter counts are indicated by the dash-dotted orange lines.