  We report the results of a multi-waveband analysis of the masses and
luminosities of $\sim$600 galaxy groups and clusters identified in the maxBCG
catalogue. These data are intended to form the basis of future work on the
formation of the "$m_{12}$ gap" in galaxy groups and clusters. We use SDSS
spectroscopy and $g$, $r$ and $i$ band photometry to estimate galaxy
group/cluster virial radii, masses and total luminosities. In order to
establish the robustness of our results, we compare them with literature
studies that utilize a variety of mass determinations techniques (dynamical,
X-ray, weak lensing) and total luminosities estimated in the $B$, $r$, $i$, and
$K$ wavebands. We also compare our results to predictions derived from the
Millennium Simulation. We find that, once selection effects are properly
accounted for, excellent agreement exists between our results and the
literature with the exception of a single observational study. We also find
that the Millennium Simulation does an excellent job of predicting the effects
of our selection criteria. Our results show that, over the mass range
$\sim10^{13}-10^{15}$ M$_{\odot}$, variations in the slope of the
mass-luminosity scaling relation with mass detected in this and many other
literature studies is in part the result of selection effects. We show that
this can have serious ramifications on attempts to determine how the
mass-to-light ratio of galaxy groups and cluster varies with mass.
