Graphical explanation of the BCD spectrophotometric parameters (D,λ₁,Φ_b,Φ_uv). In a) the determination of the BCD parameters is shown for a star in a B-normal type phase; b) displays a Be star whose second component of the Balmer discontinuity is in emission (flux excess); c) is for a Be-shell phase where the second component of the Balmer discontinuity appears in absorption (flux deficiency). The parameter D_∗ (heavy full line) that measures the photospheric component of the Balmer discontinuity is given in dex, while the average spectral position of the Balmer discontinuity is generally given in λ₁−3700 Å. In stars with a second component in emission or in absorption the parameter Φ_uv is generally not measured.