  We present high-speed, three-colour photometry of the faint eclipsing
cataclysmic variables XZ Eri and DV UMa. We determine the system parameters
through two techniques: first, timings of the eclipse contact phases of the
white dwarf and bright-spot using the derivative of the light curve; and
secondly, a parameterized model of the eclipse fitted to the observed light
curve by chi-squared minimisation. For both objects, we prefer the latter
method, as it is less affected by photon noise and rapid flickering. For XZ Eri
we obtain a mass ratio q = 0.1098 +/- 0.0017 and an orbital inclination i =
80.16 +/- 0.09 degrees. For DV UMa we derive figures of q = 0.1506 +/- 0.0009
and i = 84.24 +/- 0.07 degrees. The secondary star in XZ Eri has a very low
mass Mr/Msun = 0.0842 +/- 0.0024, placing it close to the upper limit on the
mass of a brown dwarf.
