The x-axis is the total spotted area in percentage of the whole stellar surface area. The y-axis is the effective – i.e. observed – limb darkening coefficients relative to the table value at the given stellar efffective temperature. For this figure we used T_star = 5775 K and T_spots = 3775 K, and the positions of the spots were chosen randomly on the visible hemisphere. The size of the spots were always the same, so higher spot coverage corresponds to larger number of spots. The limb darkening coefficients were taken from Claret & Bloemen (2011) for R-band, log g = 4.5 and at solar metallicity at these temperatures. Effects of faculae were not considered in this figure.