  Photometric redshifts are used to determine the rest frame luminosity
function (LF) of both early-type and late-type galaxies to M_B ~ -17.6 for the
cluster Cl1601+42 at z = 0.54. The total LF shows a steep faint-end slope alpha
\~ -1.4, indicating the existence of a numerous population of dwarf galaxies.
Luminous galaxies, with M_B < -19.5 are mostly red, early-type galaxies, with a
LF best described by a Gaussian. Faint galaxies are predominantly blue,
late-type galaxies, well fitted by a Schechter function with alpha ~ -1.7.
Compared to clusters at lower redshift, the steepening of the faint end starts
at brighter magnitudes for Cl1601+42, which may indicate a brightening of
todays dwarf population relative to the giant population with increasing
redshift. Early-type galaxies are centrally concentrated, and dominate the core
region, implying that the radial gradient of early-type galaxies seen in local
clusters is already established at z ~ 0.5. Bright, late-type galaxies are
rare, consistent with a decrease in star formation in field galaxies as they
are accreted on to the cluster, while faint, blue galaxies are evenly
distributed across the cluster, except for a depletion in the core region. The
blue fraction is f_B ~ 0.15, which is somewhat lower than the Butcher-Oemler
average at z ~ 0.5. The value of f_B is found to increase with limiting
magnitude and with radius from the centre.
