Low-resolution spectra for two different Be stars illustrating the cases for sBD in absorption and in emission. The different components of the BD are indicated: D (total), D^* (photospheric), and d (circumstellar). The straight green lines at λ > 3700 Å and λ < 3700 Å represent the rectified Paschen and Balmer continuum flux. The vertical dashed line indicates the wavelength λ 3700 Å at which the flux ratios are measured. The dotted green line represents logF₊₃₇₀₀ − D^*∕2, and is used to determine the λ₁ parameter, whose abscissa is indicated with a vertical arrow (see Sect. 2.1.1.).