Observed (upper left), corrected for [NII] contamination (upper right), and corrected for [NII] contamination and dust attenuation (lower left) Hα luminosity functions of the Virgo cluster. Filled black dots show the whole Virgo cluster sample, and filled red and blue dots show the HI-deficient (HI-def > 0.4) and HI-normal (HI-def ≤ 0.4) cluster galaxies. The black and red dots overlap for L(Hα) < 10³⁸ erg s⁻¹. The vertical dotted and dashed black lines indicate the expected Hα luminosity for a single O3 and B0 star, respectively. The solid black line and dotted grey lines show the best-fit and 1σ confidence regions for the Schechter luminosity function parametrisation. The small panels in the top right corner indicate the 1σ probability distribution of the fitted Schecheter function parameters in the three luminosity functions. The same parameters are compared in the lower right panel.