Editing F-number (section)

== Camera equation (G#) ==

The camera equation, or G#, is the ratio of the [[radiance]] reaching the camera sensor to the [[irradiance]] on the focal plane of the [[camera lens]]:<ref name="g-number">{{cite book |last1=Driggers |first1=Ronald G. |title=Encyclopedia of Optical Engineering: Pho-Z, pages 2049-3050 |date=2003 |publisher=CRC Press |isbn=978-0-8247-4252-2 |url=https://books.google.com/books?id=rcrGlrguj1YC |access-date=18 June 2020 |language=en}}</ref>

<math display=block>G\# = \frac {1 + 4 N^2} {\tau \pi} \,,</math>

where {{mvar|τ}} is the transmission coefficient of the lens, and the units are in inverse [[steradian]]s (sr<sup>−1</sup>).