  We present a novel method to extract the various contributions to the
photonic local density of states from near-field fluorescence maps. The
approach is based on the simultaneous mapping of the fluorescence intensity and
decay rate, and on the rigorous application of the reciprocity theorem. It
allows us to separate the contributions of the radiative and the apparent
non-radiative local density of states to the change in the decay rate. The
apparent non-radiative contribution accounts for losses due to radiation out of
the detection solid angle and to absorption in the environment. Data analysis
relies on a new analytical calculation, and does not require the use of
numerical simulations. One of the most relevant applications of the method is
the characterization of nanostructures aimed at maximizing the number of
photons emitted in the detection solid angle, which is a crucial issue in
modern nanophotonics.
