Impact of the photometric errors (x-axis) on the distribution of retrieved time-lag measurements. Upper panel: μ = 0.5. Three different values of f_BLR are shown as squares, stars, and diamonds. Lower panel: f_BLR = 0.2. Three different values of μ are shown as stars, squares and diamonds. The dashed black line shows the input time lag τ = 100 days and the solid black line the median lag measured on light curves free of noise. The points with the same photometric uncertainty (i.e. squares, stars, and diamonds) have been slightly shifted between each other towards larger uncertainty to ease legibility. In both panels, the solid blue squares correspond to our fiducial case for different photometric accuracies.