  Single molecule localization microscopy (SMLM) permits the visualization of
cellular structures an order of magnitude smaller than the diffraction limit of
visible light, and an accurate, objective evaluation of the resolution of an
SMLM dataset is an essential aspect of the image processing and analysis
pipeline. Here we present a simple method that uses the pair autocorrelation
function evaluated both in space and time to measure the time-interval
dependent point-spread function of SMLM images of static samples. Using this
approach, we demonstrate that experimentally obtained images typically have
effective point spread functions that are broader than expected from the
localization precision alone, due to additional uncertainty arising from drift
and drift correction algorithms. This resolution metric reports on how
precisely one can measure pairwise distances between labeled objects and is
complementary to the commonly used Fourier Ring Correlation metric that also
considers spatial sampling. The method is demonstrated on simulated
localizations, DNA origami rulers, and cellular structures labelled by
dye-conjugated antibodies or fluorescent fusion proteins.
