Lens Focal Length Tutorial

By: IPVM Team, Published on Jul 10, 2019

3mm, 6mm, 2.8 - 9mm, 5 - 50mm, etc.

Camera specifications often list lens lengths but what do they mean?

Free image1 1

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

***, ***, *.* - 9mm, * - ****, etc.

****** ************** ***** **** lens ******* *** **** do **** ****?

Free image1 1

***** ******* *** ********* in *********** *** ******* camera ******** *** ***** of **** (***). ** this ********, ** **** at:

  • **** **** ***** ****** impacts
  • *** ************ ** ****** size
  • ****** **** ****** ****** and ***** ****
  • *********** ** ***** ***** lens ******
  • ************ ********* ******* ***** length *** ***
  • ***** **. ********* ******
  • ***** ***** ****** *******
  • ***** ****** ****** ** camera ****
  • **** *********** (*** ***** performance *** ****** ****)
  • ******* *** ***** **** length

[***************]

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

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

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

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

lens focal length

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

narrow

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

wide

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 *******:

Angle of View Differences

** ***** ***** *******, 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 ******.

Fixed Focal Lenses Much Smaller2 REV1 1

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

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

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

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

05lx

  • ***** ** ***** ******: ************ ******* **** 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 (7)

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

Login to read this IPVM report.
Why do I need to log in?
IPVM conducts unique testing and research funded by member's payments enabling us to offer the most independent, accurate and in-depth information.

Related Reports

Camera Course Winter 2020 on Jan 10, 2020
This is the only independent surveillance camera course, based on in-depth product and technology testing. Lots of manufacturer training exists...
IPVM Camera Calculator User Manual / Guide on Oct 16, 2019
Learn how to use the IPVM Camera Calculator (updated for Version 3.1). The guide below includes instructions, images, gifs, and videos...
Camera Focusing Tutorial on Oct 14, 2019
Camera focus is fundamental to quality imaging. Mistakes can significantly reduce details, making cameras less effective. In this guide, we...
PlateSmart LPR Profile on Jan 31, 2019
PlateSmart Technologies claims to "turn any conventional surveillance camera into a license plate recognition camera" We spoke with PlateSmart to...
Hanwha Smaller Multi Imager Tested (PNM-9000VQ) on Feb 14, 2019
Hanwha's first repositionable multi imager PNM-9081VQ tested well, but was huge, over 12" wide and weighing in at over 10 pounds. Now, they have...
Axis IR Multi Imager Camera Tested (P3717-PLE) on Feb 18, 2019
Axis has released their first IR multi imager, the P3717-PLE, a repositionable model listing 360° IR illumination and flexible positioning,...
Panasonic 32MP Multi Imager Camera Tested (WV-X8570N) on May 16, 2019
Panasonic has released their first multi imager models including the 32MP (4x4K) WV-X8570N, claiming "Extreme image quality for evidence capturing...
Lens Iris Tutorial on Aug 08, 2019
Cameras, like humans, have irises, controlling the light which hits the imager and impacting image details. However, cameras have multiple types of...
Camera Field of View (FoV) Guide on Nov 13, 2019
Field of View (FoV) and Angle of View (AoV), are deceptively complex. At their most basic, they simply describe what the camera can "see" and seem...
Lasers Impact on Surveillance Cameras Tested on Sep 25, 2019
Hong Kong protests have brought global attention to video surveillance and the ongoing attempts of protesters to disable or undermine those cameras...

Most Recent Industry Reports

Brivo Business Profile 2020 on Jan 27, 2020
Brivo has been doing cloud access for more than 20 years. Is the 2020s the decade that cloud access becomes the norm? CEO Steve Van Till recently...
Favorite VMS / NVR Manufacturers 2020 on Jan 27, 2020
In 2018, a new winner emerged and a former top choice declined. Now, there is a new #1, a new top 5 finisher and 2 major VMSes in decline. Our...
"Hikvision Football Arena" Lithuania Causes Controversy on Jan 24, 2020
Controversy has arisen in Lithuania over Hikvision becoming a soccer team's top sponsor and gaining naming rights to their arena, with one local MP...
Axis and Genetec Drop IFSEC 2020 on Jan 23, 2020
Two of the best-known video surveillance manufacturers are dropping IFSEC International 2020, joining Milestone who dropped IFSEC in 2019. The...
Multipoint Door Lock Tutorial on Jan 23, 2020
Despite widespread use, locked doors are notoriously weak at stopping entry, and thousands can be misspent on locks that leave doors quite...
Avigilon Shifts Cloud Strategy - Merges Blue and ACC on Jan 23, 2020
Avigilon is shifting its cloud strategy, phasing out its Blue web-managed surveillance platform as a stand-alone brand and merging it with its ACC...
Verkada Paying $100 For Referrals Just To Demo on Jan 22, 2020
Some companies pay for referrals when the referral becomes a customer. Verkada is taking it to the next level - paying $100 referrals fees simply...
Camera Analytics Shootout 2020 - Avigilon, Axis, Bosch, Dahua, Hanwha, Hikvision, Uniview, Vivotek on Jan 22, 2020
Analytics are hot again, thanks to a slew of AI-powered cameras, but whose analytics really work? And how do these new smart cameras compare to top...
Intersec 2020 Final Show Report on Jan 21, 2020
IPVM spent all 3 days at the Intersec 2020 show interviewing various companies and finding key trends. We cover: Middle East Enterprise...
Vehicle & Long Range Access Reader Tutorial on Jan 21, 2020
One of the classic challenges for access control are parking lots and garages, where the user's credential is far from the reader. With modern...