Using the Millennium Galaxy Catalogue we quantify the dependency of the disc and bulge luminosity functions on galaxy inclination .
Using a contemporary dust model we show that our results are consistent with galaxy discs being optically thick in their central regions ( \tau _ { B } ^ { f } = 3.8 \pm 0.7 ) .
As a consequence the measured B -band fluxes of bulges can be severely attenuated by 50 % to 95 % depending on disc inclination .
We argue that a galaxy ’ s optical appearance can be radically transformed by simply removing the dust , e.g .
during cluster infall , with mid-type galaxies becoming earlier , redder , and more luminous .
Finally we derive the mean photon escape fraction from the integrated galaxy population over the 0.1 \mu m to 2.1 \mu m range , and use this to show that the energy of starlight absorbed by dust ( in our model ) is in close agreement with the total far-IR emission .