Editing Shot noise (section)

===Detectors===
The flux signal that is incident on a [[detector]] is calculated as follows, in units of photons:
<math display="block">P = \frac {\Phi \, \Delta t} {\frac {hc}{\lambda}} </math>

where ''c'' is the [[speed of light]], and ''h'' is the [[Planck constant]].  Following Poisson statistics, the [[photon noise]] is calculated as the square root of the signal:
<math display="block">S = \sqrt {P} </math>

The SNR for a CCD camera can be calculated from the following equation:<ref>{{cite web |title=Signal-to-Noise Ratio |url=https://www.photometrics.com/learn/imaging-topics/signal-to-noise-ratio |website=Teledyne Photometrics |access-date=8 March 2022}}</ref><ref>{{cite web |title=CCD Noise Sources and Signal-to-Noise Ratio |url=https://hamamatsu.magnet.fsu.edu/articles/ccdsnr.html |website=Hamamatsu Learning Center |access-date=8 May 2025}}</ref>
<math display="block">\mathrm{SNR} = \frac {I\cdot QE\cdot t} {\sqrt {I\cdot QE\cdot t + N_d\cdot t + N_r^2}}, </math>
where:
*''I'' = photon flux (photons/pixel/second), 
*''QE'' = quantum efficiency, 
*''t'' = integration time (seconds), 
*''N''<sub>''d''</sub> = dark current (electrons/pixel/sec), 
*''N''<sub>''r''</sub> = read noise (electrons).