  The use of light front coordinates allows a fully relativistic description of
a hadron's spatial densities to be obtained. These densities must be
two-dimensional and transverse to a chosen spatial direction. We explore their
relationship to the three-dimensional, non-relativistic densities, with a focus
on densities associated with the energy momentum tensor. The two-dimensional
non-relativistic densities can be obtained from the light front densities
through a non-relativistic limit, and can subsequently be transformed into
three-dimensional non-relativistic densities through an inverse Abel transform.
However, this operation is not invertible, and moreover the application of the
inverse Abel transform to the light front densities does not produce a
physically meaningful result. We additionally find that the Abel transforms of
so-called Breit-frame densities generally differ significantly from the true
light front densities. Numerical examples are provided to illustrate the
various differences between the light front, Breit frame, and non-relativistic
treatment of densities.
