Luminosity Functions
Features to note
Morphology matters, also field vs. cluster.
L* or M* in rich clusters isn’t a bad “standard candle”
cD galaxies in cluster centers are special cases; they are
like massive ellipticals but have extra stellar envelopes.
They do not fit extrapolations of ellipitical LFs.
Low luminosity end of LFs not well determined (Irr and
dwarf ellipticals).  Again SDSS will probably be the best
word on this (if it goes faint enough).