  Current generation stellar isochrone models exhibit non-negligible
discrepancies due to variations in the input physics. The success of each model
is determined by how well it fits the observations, and this paper aims to
disentangle contributions from the various physical inputs. New deep,
wide-field optical and near-infrared photometry ($UBVRIJHK_S$) of the cluster
M35 is presented, against which several isochrone systems are compared: Padova,
PARSEC, Dartmouth and Y$^2$. Two different atmosphere models are applied to
each isochrone: ATLAS9 and BT-Settl. For any isochrone set and atmosphere
model, observed data are accurately reproduced for all stars more massive then
$0.7$ M$_\odot$. For stars less massive than 0.7 M$_\odot$, Padova and PARSEC
isochrones consistently produce higher temperatures than observed. Dartmouth
and Y$^2$ isochrones with BT-Settl atmospheres reproduce optical data
accurately, however they appear too blue in IR colors. It is speculated that
molecular contributions to stellar spectra in the near-infrared may not be
fully explored, and that future study may reconcile these differences.
