  We compute the Landau gauge quark propagator from lattice QCD with two
flavors of dynamical O(a)-improved Wilson fermions. The calculation is carried
out with lattice spacings ranging from 0.06 fm to 0.08 fm, with quark masses
corresponding to pion masses of 420, 290 and 150 MeV, and for volumes of up to
(4.5fm)^4. Our ensembles allow us to evaluate lattice spacing, volume and quark
mass effects. We find that the quark wave function which is suppressed in the
infrared, is further suppressed as the quark mass is reduced, but the
suppression is weakened as the volume is increased. The quark mass function
M(p^2) shows only a weak volume dependence. Hypercubic artefacts beyond O(a)
are reduced by applying both cylinder cuts and H4 extrapolations. The H4
extrapolation shifts the quark wave function systematically upwards but does
not perform well for the mass function.
