  We demonstrate that the maximum-entropy method for gravitational lens
reconstruction presented in Bridle et al. (1998) may be applied even when only
shear \emph{or} magnification information is present. We also demonstrate that
the method can easily handle irregularly shaped observing fields and, because
shear is a non-local function of the lensing mass, reconstructions that use
shear information can successfully bridge small gaps in observations. For our
simulations we use a mass density distribution that is realistic for a z=0.4
cluster of total mass around 10^15 h^-1 M_solar. Using HST-quality shear data
alone, covering the area of four WFPC2 observations, we detect 60 per cent of
the mass of the cluster within the area observed, despite the mass sheet
degeneracy. This is qualitatively because the shear provides information about
the variations in the mass distribution, and our prior includes a positivity
constraint. We investigate the effect of using various sizes of observing field
and find that 50 to 100 per cent of the cluster mass is detected, depending on
the observing strategy and cluster shape. Finally we demonstrate how this
method can cope with strong lensing regions of a mass distribution.
