Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
It could be useful the following:
"The Role of Photon Statistics in Fluorescence Anisotropy Imaging" by Lidke
et al.
They use multiple images of the same object to compute a variance from which
you may infer the number of collected photons in the assumption that only
poissonian noise is present.
Cheers,
Alessandro
--
Dr. Alessandro Esposito
Laser Analytics Group - Department of Chemical Engineering
University Cambridge
CV: home.quantitative-microscopy.org
Web: wikiscope.org