Light curve of a source in the field of M4 (MatchID = 27382770; WFC3_F775W filter), demonstrating the application of the preprocessing procedure. The figure shows the original light curve retrieved from the HSC (top), the local-corrected light curve (middle), and the final cleaned light curve (bottom). For clarity, the light curves are offset by 0.2 mag. In each step of the procedure, the outliers (>3σ′; red circles) and potential outliers (<3σ′ and >4σ_syn; blue squares) are marked. Outliers that also have a large synthetic error (>4σ_syn) are marked by green diamonds.