Illustration of how our EW measurement method works on an observed Hβ line: in the upper panel we show how the EW is iteratively measured at increasingly larger Δλ (red, straight line) which are also used to define the continuum level. The dashed regions correspond to the area measured for the EW determination. The analysis of the EW trend curve, plotted on the lower panel, provides the correct observed value, shown by the red cross. In this case, in which both emission and absorption components are present, it corresponds to the second zero of the first derivative of the trend curve itself.