Lens Focal Length Tutorial

By IPVM Team, Published Jul 10, 2019, 11:44am EDT

Camera specifications often list focal lengths, e.g., 3mm, 6mm, 2.8 - 9mm, 5 - 50mm, but what do these specs really mean?

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These metrics are important in determining the correct camera coverage and Field of View (FoV). In this tutorial, we look at:

  • What lens focal length impacts
  • The relationship of imager size
  • Common lens length ranges and their uses
  • Limitations of using focal lens length
  • Manufacturer variances between focal length and AoV
  • Fixed vs. varifocal lenses
  • Fixed focal length options
  • Focal length impact on camera size
  • Lens limitations (low light performance and detail loss)
  • Picking the right lens length

Focal **** ****** ** *** / ***

***** **** ****** ** the ******** ******** ******* the **** *** *** sensor / ******. ** is ********* ** ************ because ** ** *** primary ****** ** *** FoV ******* / ***** of **** (***) ** a *****. ***:***** ** **** (***) Tutorial.

Lens ****** ******

*** ****** *** ****, the ******** *** ***** of **** / **** captured; *** ******* *** lens, *** *****. **** is * ******** ********* deriving **** *** ******** between *** **** *** the ******, ** *** image ***** *****:

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*** ****** *** **** is, *** ******* ** is **** **** *** imager, ********* ** * narrower ***.

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********, ** *** **** is *****, ** **** be ***** ** *** imager *** ******* * wider ****, **** **:

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Impact ** ****** ****

****** *** ***** **** length ** *** ******* driver ** *** ** surveillance, *** **** ** imager **** (*.*., */*”,*/*”,*/*”, etc.) **** ******* ****. Everything **** *****, *** larger *** ******, *** wider *** ***** ** view **** ** ** the **** ***** ******.

**** ******* **** **** imager **** ***** **** close, **** ** */*.*" vs. */*.*" **. */*", the **** ****** ******* in *** ** ****. This ***** ********** ** imager **** *** ****** in ******* ******* ********** in ***** ** ****, leading ** ***** ** narrower ***** ** **** than ********. ** **** distances, **** *** ****** to ******* **** ** more, ***** ** ***** ranges ** *** **** no ********* **********.

*** *******, *** ***** below ***** *** *********** in *********** ***** ** view ******* */*" *** 1/2.7" ******* ***** ******* lens *******:

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** ***** ***** *******, differences *** **** **********,**** the */*.*" ****** ********* a ******* ***** ***** of **** **** */*", which ***** ****** ** lower **** ******** *******.

*** ***** ************ ** your *** ******** **** **********.

Common **** ****** ******

** ********, ************ ******* typically **** ** *** of * **** ****** ranges:

  • ******* / ***** ***:******** ***** **** ***** views *** ***** **** distortion, **** *** **** 'fisheye'. ***** ****** ********* require ********* ******** ** provide * **** / corrected *****. ***** ** can ******* ********* ******, implementation *********** ******. *** our ***** ** ********* Panoramic / *** ******* cameras.
  • '******' / *** – 10mm:*** ***** ****** ** most ******* **** ** this ***** (******* ** to ** ******* ***).
  • ********* / **** – 80mm:***** **** ******* ** no **** **** ****** in **** *****, **** of ******** */** ****** *** be ********* *** ********* to ******* (********* *** form ******)
  • ***** ********* / *****+:****** ** **** ***** are ********** **** **** to *** / ******* objects **** *** **** (typically ***+ **** ***** 5kms ** ****)

Warning: ************ ***** ****** / *** *********

****** ************* ********* ******* AoV / *** ********* by ******* * ***** length. *** *******, ************* may **** *** *********** to **** **** * camera ** **** ***** or ********* **** ** show * ****** ** telephoto.

*******, ****** ************'* ***** lengths ** *** ****** map ** ** *********** / ************ *** *** , ********** **** ******* focal *******. ********* ** is ******* ** *** much ** *** ****** or **** ** **** or ******* *** ************ of *** **** ****** from *** *********** ************.

********** ** *** *****, the ******** ** ** always **** ******* / lenses ***** ** ***, not ***** ******. **** makes **** **** ********** ********* ** ****** models, **** ******** ****, in *** **********.

Fixed ***** **. ********* ******

** ************ ***** *** two *** **** *****, fixed ***** *** *********.

  • ***** *****: ***** ***** lenses *** ****** **** one ***** ******, *.*., 2.8mm, ***, ****, ***. Their **** ********** *** simplicity (***** ** ****** adjustment ** ********) *** size (********* **** *****), though **** *** **** flexible **** ********* ****** and ****** ** **** tuned ** *** ******** desired ****** ** ****.
  • *********: ********* ****** ***** adjustment ** *** ***** length, ****** ******** ******** using *** ******** ***** or **** * ********* mechanism. ********* ****** *** specified ***** ***** ***** length *****, **** ** 2.8-10mm ** **-****. ********* models *** **** ********, as **** *** ** adjusted ** *** *** field ** **** *******, but **** *** ****** and **** *********, ********* bigger ********.

*** ******** ** ******* which *********** ******* *** varifocal (*** *** **********). *******, **** ******** depends ** * ***** integrator's ****** ******(*), **** those ******* ** ***** end ******* ***** **** fixed ***** ****** *** to ***** (*********) ***** cost.

Multiple ***** ***** ****** *******

************* *** ******* ***** focal ****** ****** ***** offer ******** **** *******. While **** ** *** as ******** ** ***** varifocal ****** ***** ***** fine, ** ****** *** some

*** *******, ******* ** a********* **-**********-*(* *** **** ****** camera), ** ** ******* with * ********* **** options, ******* **** **** angle ** ********* (****** **** ** ***** models):

  • *.***/***° ***
  • ***/**.*° ***
  • ***/**° ***
  • ***/**° ***
  • ****/**° ***

**** ****** ***** ** select *** **** ***** best **** ***** *****, e.g. ***** *** *.*** lens *** **** ******** of * ***** ***** or ***** *** **** model *** ******* ******** of * ******* *** entrance.

***** *** ***** ************ offers *** ***** *******, many ** *** ***** cost ****** ********* **, such *******,******'* * ******,********* *****/***********,*******, ***.

Focal ****** ******* ****** ****

****** ***, ***** ***** length ****** **** ** less *****, ******** ****** housings ** ** ******* than ****** ********* ** motorized ******.

*** *******, *** ***** below ***** * ***** focal ****** *** ****, typical ** ***** **** in******** *********** ** * *** camera **** **** ********. The **** ** **** lens ****** ******** *** cameras ** ** ******.

*** ********* **** ****** ******** **** ********** ** size ******.

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Lens ***********

*** ****** *** **** length, *** **** ****** three *********** **** *****:

  • ******** ***** *******: **** ******, ********** varifocal **** ****** ** surveillance, ********** **** ******** image ******* ******** ** what ***** ******* / ppf ******* ***** ********. If *** *** ******** / ***** **** **** ***********, you *** **** ** compensate **** ***** ***** density. ***:* ***** **** ** Long ****** *** **** Found

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  • ******** *** ***** ***********: **** **** ****** (as **** ** **** short ****) ********* **** significantly **** ***** **** typical ****** ** *** 3mm ** **** *****. Specifically, ********** **** ***** equal, *** ****** *** lens *** ****** *** F ******.****** *** * **** tutorial *** *******.

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  • ***** ** ***** ******: ************ ******* **** rarely **** ***** ** field ****** ***** ******* appear *** ** *****. This ** ******* **** usually *** ********** ***** lenses *** **** ******** that *** **** **** 5 **** **** **** the ******. *******, **** long **** **** ***** problems **** *** ********** hard ** ******* *** night **** ******* ** with ****-**** ******. ****** our***** ** ***** ********.

Picking *** ***** **** ******

*** ******* *** **** length, *** **** *** camera *** *******. *************, the ***** *** ******* area, *** **** ******** is *** ********** ****** captured. **** ** *** people ***** *** ******* when **** **** ** a ***+ ******* *******. Since ** ** **** resolution, *** ******* "******" be ****** *** ***** the *** ** ** huge, *** *** ******* can **** "*****" **** at ***** *****.

*** **** **** ** thumb ** ** **** the *** ** ***** than *** **** ** interest – *.*., **** what *** **** ** capture. *******, **** *** be ***** ** ****** want ** ******* * lot ** ****** (*.*., I **** *** **** in *** ******* *** plus *** ******* ****** of *** **** ******** it).

** **** ***** ****, Pixels *** **** (***) / ****** *** ***** are ******* **** ** help ********* *** **** one *** ** ******* making *** ******* ** the **** ******** ** fuzzy **** **** **** no *****. ********** *** *** ******* ********** ****. ********** with *** ****** ********** to ********* *** ******* trade *** ******* *** and *** *** **** specific ************.

[**** **** **** ******** was ********** ********* ** 2011, *** *** ******* in **** *** **** with **** ******** ******** and ********** *-**** *** iCS **** ***********.]

Comments (13)

***** **** ****** ** the**************** ******* *** **** and *** ****** / imager. (******** *****).

** ** ********** **’* not, ******** ****** ***** lengths ********* ******** *** physically ******.

****’* * ****** ** examples:

***** ** * ***** focal ****** ***.  ******* even ****** ** *** back-focus ******** (***** **** the **** ***** ** the ******), **’* ****** 3x *** ****** ***********.

**** ** * ******** 8-48mm ****, ***** ********.

** ***** ** ****.

*********, **** ** **** a ****** ** ****** that * **** ******* around.  *’* ** ********** in ****** **** ****** find.

**** ***** *** ******* cases **** ** *** following ****; ***** ***** length ******* ** * 410mm *** (********* *** sensor/connectors *** *******)

****, *** ****** ** millimeters ** * ***** “focal ******”, ***** ********** when *********** ***, ** unlikely ** ********** ** a ******** ****** *** can ******** ******* **** camera/lens ** ****.

** *******, **'* *** physical ******** ******* *** imager *** *** ****' point ** *********** (***** below). ** ** *** case ** **** *** lenses, *** ***** ****** is ****** ********* ** the ****** ** *** lens. **** ****** *** made ** ** ******* elements (**** ***** *****) and *** *********** ***** hits ** *** ** these ********.

** *** **** ** the **** ******, *'* not ***% **** **** they're ***** *****. **** could ** ***** ********** *********** ***** ****, ***** magnifies *** ****** ******* of *** ***** ** increase *** ********* ***** length. ****'** ****** ** photography, ****** **** *** available** ************** ****. ** **** see **** ** *** find ***.

** *******, **'* *** physical ******** ******* *** imager *** *** ****' point ** *********** (***** below).

**** ******* *** *** convergence ***** ***** ** the ****** ******, (** i’m ******* ** *********).  i **** *** *** diagram.

******* * **** ***** professional ******* ********** ** measure ****** ***** ****** of **** **** ********* FA ******. ****** ***** varies ** ** **%. What ***** ** ****** from ***** ***** **** in **** ? 

**** ***** *** ** valuable. 

* **** ** ** ago, ******* ****** * great ***** ******* *** to ******** ******* ****** and ********* *** *** (depth ** *****?). *** video ****** * *** walking * **** **** distance ** * ******* lot ******* *** ****** - ** *** ***** poorly ********** *******, *** man *** ***************** ***** he *** **** ***** to *** ****** *** the ******** ** ****** looked ****** ****.  ** the ******** ********** ****, the ***** ** *** parking *** ****** ********* and *** *** ******** to **** ******* **** though ** *** *** same ******** *** *** image ** *** ****** was ******* *****.

** **** ****** ********, I'd **** ** *** that *****/**** *****.  * think *** ****** *** posted ** *** * Consultant.

**** ** ** ********* focal ****** ******. 

******** *** ***** ** get ** **** ****** as *** ****** **** [Tariffs, ***] *** **** info.

**, * **** * question, **** ****, ********** with *********, ** ********* camera, *** **** ** get *********? ** ********* lens, **** * ****** manual *.*-**** ****.

******: **** ******* *** been ***** ** *** own **********:**** ****, *** **** An ********* ****** *** Unfocused?

**** *** ***** ** detail. **** ******* *** video ***** *** ******* assignment. * *** *** it's ********* ** ** the ******* *****. ***** the ***** ******** * lot **** **************.

***** *********** ** *** the **** ***** *** there ********** ************. *** impact ** *** ****** of *** **** ** a ****-****** ************* **** selecting ** **** ** install *** * ********.

**** ** *** ******** "While **** ** *** as ******** ** ***** varifocal ****** ***** ***** fine, ** ****** *** some” ******** ** ***?

** **** ****;

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

******!

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**, *** *** ******* the ****** ********** ******* (generic ******) ** **** of;

"********** **** *****, *** larger *** ******, *** wider *** ***** ** view **** ** ** the **** ***** ******."

*** */*.*” ****** ****** has ** ** ****** ratio **** ***** *** width ******* **** *** 1/2.7”, ** *** ******* of *** ****** ** course.

**’* ***** **** ********** that *** ****** *********, e.g. */*.*”, ** * inexact ******** *************, ******* ********: **** ** The **** ** ** Of * */*" ******?

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