Noise-equivalent flux density
In optics the noise-equivalent flux density or noise-equivalent irradiance of a system is the level of flux density required to be equivalent to the noise present in the system. It is a measure used by astronomers in determining the accuracy of observations.
The NEFD can be related to a light detector's Noise-equivalent power for a collection area A and a photon bandwidth by:
, where a factor accounts for the photon statistics for the mode of operation.
