Joint 1σ error ellipses for the parameters { α,γ,σ } of the scaling relation , obtained from the Fisher-matrix analysis in real (shaded area) and redshift (dotted lines contours) space, using the set r_{ν = 1, ··· , 7}(L) defined in Eq. (7) as observables. The small filled contours represent the results using the XLF.