  I propose an analysis method, based on spin-spherical harmonics and spherical
Bessel functions, for large-scale weak lensing surveys which have source
distance information through photometric redshifts. I show that the distance
information can significantly reduce statistical errors on cosmological
parameters; in particular, 3D lensing analysis offers excellent prospects for
constraining the equation of state of the vacuum energy which dominates the
energy density of the Universe. I show that the ratio of pressure to energy
density could be determined to an accuracy of $\sim 1%$ or better. Having
distance information also offers significant advantages in the control of
systematic effects such as the intrinsic alignment of galaxies. The case for
obtaining photometric redshifts is therefore compelling. A signal-to-noise
eigenmode analysis of the modes shows that the modes with highest
signal-to-noise correspond quite closely to ignoring the redshift information,
but there is significant extra information from a few radial modes. These modes
are generally long-wavelength, suggesting that useful information can be
gleaned even if the photometric redshifts are relatively inaccurate.
