  We demonstrate a novel procedure to calibrate neutron detection systems
commonly used in standard neutron radiography. This calibration allows
determining the uncertainties due to Poisson-like neutron counting statistics
for each individual pixel of a radiographic image. The obtained statistical
errors are necessary in order to perform a correct quantitative analysis. This
fast and convenient method is applied to data measured at the cold neutron
radiography facility ICON at the Paul Scherrer Institute. Moreover, from the
results the effective neutron flux at the beam line is determined.
