  We examine the impact of using photometric redshifts for studying the
evolution of both the global galaxy luminosity function (LF) and that for
different galaxy types. To this end we compare LFs obtained using photometric
redshifts from the CFHT Legacy Survey (CFHTLS) D1 field with those from the
spectroscopic survey VIMOS VLT Deep Survey (VVDS) comprising ~4800 galaxies. We
find that for z<2, in the interval of magnitudes considered by this survey, the
LFs obtained using photometric and spectroscopic redshifts show a remarkable
agreement. This good agreement led us to use all four Deep fields of CFHTLS
comprising ~386000 galaxies to compute the LF of the combined fields and
estimate directly the error in the parameters based on field-to-field
variation. We find that the characteristic absolute magnitude M* of Schechter
fits fades by ~0.7mag from z~1.8 to z~0.3, while the characteristic density
phi* increases by a factor of ~4 in the same redshift bin. We use the galaxy
classification provided by the template fitting program used to compute
photometric redshifts and split the sample into galaxy types. We find that
these Schechter parameters evolve differently for each galaxy type, an
indication that their evolution is a combination of several effects: galaxy
merging, star formation quenching and mass assembly. All these results are
compatible with those obtained by different spectroscopic surveys such as VVDS,
DEEP2 and zCosmos, which reinforces the fact that photometric redshifts can be
used to study galaxy evolution, at least for the redshift bins adopted so far.
This is of great interest since future very large imaging surveys containing
hundreds of millions of galaxies will allow to obtain important precise
measurements to constrain the evolution of the LF and to explore the dependence
of this evolution on morphology and/or color helping constrain the mechanisms
of galaxy evolution.
