F-Stop Tutorial

By IPVM Team, Published Dec 16, 2016, 11:00pm EST

To understand low light surveillance, appreciating the importance and role of the f-stop metric is critical. In this tutorial, we explain:

Key Points

  • *** ********* *** ***** small **** ****** ******* typically **** *** ***** f *******
  • *** *** ***** ** a *** ******* *** f-stop / *** ***** performance
  • *** ********** ** ******* f-stop 
  • *** ********* *-**** ** maximize ***** ** ***** is ********* *** ******** to **** **** ** surveillance
  • *** *-**** *** ** confusing *** ****************

*-**** ******** *** ******** amount ** ***** **** a **** *** ****. Understanding *** ******'* ************ can ** ****** ** the ****** *** * number (*, *, *, 8, ***.), *** **** amount ** ***** **** be **** (*.*., * is **** ***** **** 4, *.* ** ***** than *.*, ***.). ****'* a ****** ************ ** lens ******** ** * numbers:

fstop

***********, * **** ********* the ****** ** *** lens *** *** ******** of *** **** (*.*., L/D). ********** **** *****, the ****** *** **** (say **** ******* ** 3mm), *** **** ***** passed *** *** ****** the * ******. *********, smaller **** ******** (**** as ***** ** ********* cameras) ******* *** ******* iris, ******** **** ***** to ****, ********* ** higher * *******. **** of ***** ******** ****** practical ***********, ********** ** PTZs *** *********.

What * ******* **** ** **************

**** ****** / ******* specify * *******, **** always ******* *** ****** F ****** **** *** lens ******** **** *** iris ** *** *** way ****. ********** *** ****** ***** iris *******. **** ********, *** F ****** **** ** higher. *******, **** *** iris ** ****** *** the ***, *** ******** limitation ** *** ***** of *** **** ******. It ** **** ****** F ******, **** *** iris *** *** *** open, **** ** **** critical **** ********* *** low ***** ********** ** a ****.

Low ***** ***** ***********

*** ***** *********** ***** *********** *** impact *-**** *** ** performance. ***** *** ***** for **** **** ********.

** ~* ***, ** can ******* *** * gradual ******** ** ***** brightness, **** ********** *************** * *.* *** beyond. 

2lx

** ***** *.** ***, increasing *** *-**** ******* decreases *** ********** ** our *******, **** ***** from * *.* ** F *.*. ** **** light *****, ****** * 5.6, *** ***** ** completely ****. 

05lx

*****:

  • ***** ********** * ******* always ******* *** ****** of ***** ******, *** quickly *** ******'* ***** darkens ******* ** *** overall ***** *********** (*.*., a '****' ******* *** light ****** **** ****** getting ******* **** ****** than * '***' ***).
  • **** *** **** ***** a ****** **** * P **** **** **** allows ********** ********* * numbers ** ******** ******. This ****** ** **** with '*******' **** **** cameras *** ** ********* with ******* ****** **** lenses ******* **** ********* do *** **** ******** levels.

Integrated ** ******

******* ** *** ***** in ********** ** *** ** *** **** *** years, *-**** *** ****** somewhat **** ********. ********** IR **** *********** ******* of ***** ** *** scene, ************ *** ****** F-stops.

*** *******, *** ***** ***** shows * ***** **** our *******, **** * higher *-**** (*/*.*) ********** IR ****** ****** ************* a **** ***** *-**** non-IR ***** *** ***** model:

integrated ir compensates for higher f-stop

**** **** **** ** not ** *** ********** IR ******* **** ****** outperform ***-**, ** ** power, ******* ***** ******, super *** ***** **********/****** imagers, *** **** **** impact **** *********** ***.

Differences ** * *******

*** ********** ******* *** F ******* *** ** deceiving, ******* **** ******* on * *********** ***** instead ** ****** * linear ************. 

*** *******:

  • */*.* ***** ** **% less ***** **** */*.*
  • */*.* ***** ** **** 1/16th *** ***** ** f/1.4

***** *** *** ****'**-**** ************ *** ***** *********** themselves.

***************

***** ** ** ********* to ** ***** ** F-stop *** *** ****** it *** ****:

  • ***** *********** ** * numbers (*.*., */*.* ** f/1.4) ********* ** *** impact *** ***** *********** greatly, ******** ** **** is ******** *********.********* **** ********** ***** ****** **** image ********** ****** ***** f ****** ***********.
  • **** ************ ** *** cameras **** *-**** ******* of *.* ** *.*.
  • **** ****************** ******* *-**** *******, does *** **** ***** low ***** *********** **** be *** ****. *********** in ******* ********** **** a ******** ********** **** manufacturers ***** ******* ******* ******.
  • *******, * **** ******* of *.* ** ******* often ******** **** *** light ***********.
  • ************ ***** ***** **** factor ******* ********* *** small ****, **** ****** lens *********, **** **** high * ******* *** typically ***** *** ***** performance (*/*.* ** *******). For ********, **** **** size ***** (*** [**** ** ****** available]) **** * */*.* while ***** ********* (*** [link ** ****** *********]) have * */*.*, ******* the ********* **** ** ~1/5th *** ****** ** the **** ***** ****.
  • ******** ****** ** *** far ******* (*.*., **** focal *******) ********* **** high * ******* *** poor *** ***** *********** since ******* *** ******** a **** ***** ****** (often ** ** ******) at * **** * number (*/*.* ** ******* is ******). ****** **** manufacturers ** *** **** this *** ** ** inherent **** *** ******** stays *** **** *** the ****** ** *** lens ** *********.

Depth ** ***** ******

***** **** * ******* are *** *** *** light, **** *** ** helpful *** ********** *** depth ** ******** *** ********* ** surveillance(*** ******** ** ***** ********). *** ****** *** F ******, ********* *** greater *** ***** ** field. *** ***** ***** demonstrates ***** ** ***** at ******* *-*****:

f comparison

***** **** *** ** helpful *** ***********, ** typically **** *** **** a *** ********** ** surveillance. *****, ** *** destroy *** ******'* *** light ***********. *** *******, compared ** */*.* ****** in ************ *******, */*.* takes ** ** ***** less *****. ** **** was **** ** ** night, ** * **** environment, *** ****** ***** literally ******* ******* ****** pure *********. ******, ** auto **** ****** ***** allow */*.* ** ** used ** **** ********** as ******* *** ********** to **** *** **** as ***** ** ******** when **** (*.*., ** the **** *** * number).

*** ************** ** ** ignore ***** ** ***** optimization ****** *** **** strong *********** ****** *** are ******* ** **** negative **** ******* *** limited *********** *********** (**** during *** ***).

**** **** *********

**** **** * ******** **** ***.

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