Weak gravitational lensing of background galaxies by intervening matter directly probes the mass distribution in the universe .
This distribution , and its evolution at late times , is sensitive to both the dark energy , a negative pressure energy density component , and neutrino mass .
We examine the potential of lensing experiments to measure features of both simultaneously .
Focusing on the radial information contained in a future deep 4000 square degree survey , we find that the expected ( 1 - \sigma ) error on a neutrino mass is 0.1 eV , if the dark energy parameters are allowed to vary .
The constraints on dark energy parameters are similarly restrictive , with errors on w of 0.09 .
Much of the restrictive power on the dark energy comes not from the evolution of the gravitational potential but rather from how distances vary as a function of redshift in different cosmologies .