Varifocal vs Fixed Focal Lens

By: John Honovich, Published on May 29, 2014

Choosing between varifocal and fixed focal lens is one of the most fundamental decisions in video surveillance.

With a fixed focal lens, the Field of View (FoV) of the camera can not be changed unless the lens is changed. By contrast, varifocal lenses allow for immediate adjustment of the FoV simply by adjusting a control of the lens / camera.

But which one is used more and why?

Inside, our exclusive integrator survey results answer these questions.

******** ******* ********* *** fixed ***** **** ** one ** *** **** fundamental ********* ** ***** surveillance.

**** * ***** ***** lens, *** ***** ** View (***) ** *** camera *** *** ** changed ****** *** **** is *******. ** ********, varifocal ****** ***** *** immediate ********** ** *** FoV ****** ** ********* a ******* ** *** lens / ******.

*** ***** *** ** used **** *** ***?

******, *** ********* ********** survey ******* ****** ***** questions.

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

*********** *** ********* ****** by * *:* ****** over ***** ***** ******:

 ******, *** ******** ** integrators ****** ****** *** varifocal ****** ** **** chart ************:

*******, * ******* ** integrators ****** *** ********* lenses ** ***** ***** in *** ***** **** on *** ** ** 30% *****.

******, *** ***-***********, **** as *** **** *** DIY ******, ***** ***** lenses *** ********* *** only **** **** *******. As ****, ********* ***** segments (**** / ***), the ********** ** *** cameras ***** ***** ***** lenses ** ****** ~**%.

Why ********* ** ***** *****

***********

*** **** ****** ****** to *** ********* ******, cited ** ***********, *** to ******** *** *** for *** *** ****'* **********:

  • "********* ** **+% ** our *********** *** ** the **** ******** *** camera ** **** *** view *** ****** *****"
  • "** **** ***** **** customers **** ***** **** advantage ** *** ********* to ************** ******* ********** ***/** increase **** ** **** and ********************* ** ***** ********* need."
  • "**** **** *********** ** the *** **** *** often ***** **** **** to *** * ********** field ** ****, *** then ***** ****** *** live ***** ***** **** to ****** ***** ** tighten *** ***** ** view."
  • "** *** ********* ********* to ***** *** ********** more ******* ** ****** the***/***** ****** ** **** the ******** **********"
  • "** *********** *** ***** requirements ** ******* ** installation ******* **** *** to ******* *******, ***** technician, ***/** ********."
  • "** **** *** *********** for *** *********** ****** to ** **** ** change *** ********** ** the **** ** *** customer ******* ***** **** about **** **** **** to ** ********* ** them."

***** **** *** ***** change ***** **** ***** about *** **** * FoV **** ****, ***** the ****** ** *********, varifocal ******* *********** ** quickly **** ****.

*******, *** ********** ******* a ********* ******** ** meet ****, ******* ***** varifocal ******, ********** ****, "** stock ********* ***** ****** cameras *** **** *** whichever *** ** ********." To *** ********, ** another ********** *****, ********* "****** ** ******* *** installation **** ********** ** ***** * series ** ******."

****

*** ***** ***** ******, the ***** ****** #* reason *** ***** ****, not ****** *** *** lens ******, *** ******* fixed ***** **** ******* are ********* **** *********, less ******** ******* *******. Integrated *****:

  • "*** **** ****** ** go ***** ** ******* of ****."
  • "** *** ***** ***** lenses **** ** **** more **** ********* ********."
  • "********* **** ***********. ***** when **** ** ********."
  • "** **** ** * factor *** *** **** it **** * ********** wide ****, **** ** are **** ****** ** select *****."

*******, **** ** **** with ***********, ** *** integrator *********, "* ***** ********* ********** ** ***** but **** ********* **** worse ******* *****, *** example ** **** ** install *** & *** fixed ****'* ****** *** you **** ** ** to ****** *** ***** (varifocal) ** **** *** WDR." ****, **** ** not ******* ***** ******* cannot *********** ******* *** (indeed *** ** * sensor / ******* *************, not ****) *** ********* fixed ******* *** ********* for ****** ****, ********* features **** **** ***.

***** ***** ****** *** ******** ******* **** ********* lenses. ******, ***** ***** lenses ****** *** **** of ******* ***** *** of ***** (*** ********* do *** ********* ** as ***** ***** ****** typically **** **** * fine ***** **** *** be *** ** *****). However, ************* ********* ******* fixed ***** ****** **** simple *******, ***** **** smaller ******* ***************.

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

*********** ***** * ****** of *********** ************ ***** fixed ****** *** *** norm - **** ** fisheye /**********, ******* *** ***** high ********** *******.

Comments (13)

Rukmini Wilson

05/29/14 04:41pm

Fixed focal lenses are not lower quality than varifocal lenses...

Is it a myth that varifocal lenses have higher f-stops generally than their fixed lens counterparts, and that the difference is exacerbated as you move the varifocal towards the high range of its the focal length?

John Honovich

IPVM | In reply to Rukmini Wilson | 05/29/14 04:54pm

By definition, any time the focal width remains constant but the length increases, F stop will increase. That is typically the case with varifocal lens, i.e., adjust to a longer focal length while width remains constant.

Perhaps one could find a fixed focal length lens for a higher value (e.g., 9mm) with a lower f stop than, e.g., a 3-9mm. I've never heard, though, of someone pursuing this. Maybe though...

Andrew Lund

In reply to John Honovich | 05/30/14 06:51am

In my early days of doing surveillance video, when fixed focal length lenses were much more the norm and prepared installers usually kept a wide selection of lenses with them, I really wanted to get away from that and go with vari-focal as often as possible. I discovered Tamron, which at the time was marketing as having the only varifocal lenses on the market that maintained a constant F-stop throughout the full range of FOV adjustment. I was very pleased with the optics and mechanics of their lenses, and I did seem to get more consistent light handling throughout the FOV range than with most other brands, so they became my go-to lenses for a long time. I must confess, though, I could use an explanation on how they would have achieved this... a widening aperture as the focal length increases? Was it marketing mumbo-jumbo and the more consistent light gathering was simply because of the quality build? If it was truly an accurate claim, what other manufacturers are doing it now, too?

Rukmini Wilson

In reply to Andrew Lund | 05/30/14 08:20am

...varifocal lenses on the market that maintained a constant F-stop throughout the full range of FOV adjustment.

What's the model, do they still make it? It's hard to imagine that it could be solved by quality. Look thru a paper towel roll vs. a toilet paper roll, Charmin or not the toilet paper roll gonna win, no?

If they were widening and narrowing the aperture, and purposely restricting the best possible performance of the lens, by limiting the light, just to make their marketing claims true, that would be wrong hysterical.

Paul Galburt

05/29/14 07:23pm

In the world of photography, fixed focal length lenses (often called prime lenses) enjoy a significant quality margin over vari-focal (zoom) lenses, and generally have a smaller numerical "F" number meaning more light gathering.

Because the sensors in security cameras are so small, lower F number are relatively easier to acheive than with photographic camera lenses. Also, lower F numbers mean shallower depth of field (DOF). Shallow DOF is often prized in photography as it isolates the main subject from the background. This is almost always a real negative in security.

Also, while low F numbers are good for low-light performance, most security cameras use other means to improve low-light performance.

So, interestingly, the ideal security lens in any given situration is almost the reverse of the design of a photographic lens.

John Honovich

IPVM | In reply to Paul Galburt | 05/29/14 08:42pm

Paul, thanks for the feedback. I want to expand on one point you made:

"Also, while low F numbers are good for low-light performance, most security cameras use other means to improve low-light performance."

I agree with this. However, as a practical matter I have never seen a surveillance camera, for example, with an f/2.0 lens be good at low light. Generally, if a manufacturer wants a camera to be good at low light, they will easily spend the small delta to get an f/1.0, f/1.2, or f/1.4 lens, along with what they are spending on image processing, etc.

The one exception is integrated IR budget cameras, which generally have high f stops but include their own light source.

Rukmini Wilson

In reply to Paul Galburt | 05/30/14 01:48am

So, interestingly, the ideal security lens in any given situration is almost the reverse of the design of a photographic lens. (EA)

Interesting, yes, indubitable, no.

...most security cameras use other means to improve low-light performance.

First, although there may be 'other means' available to surveillence cameras, that's because low-light performance is so key to surveillence that other more artistic concerns, e.g. color space, low noise/distortion, are sacrificed if need be to that end. These are things that no photographic camera would dare do. But that, as John counters, doesn't mean lower F numbers are worse or even immaterial, they still comprise the front line assault against the forces of darkness, and all other things being equal, lower is better, and a lot lower is a lot better.

Also, lower F numbers mean shallower depth of field (DOF).

This is true. However true DOF issues are rarely seen in security cameras. Why? Two technical reasons:

1) Sensor size smaller sensor = deeper DOF. Witness the now ubiquitous availability of full-frame 35mm sensors in Pro DSLRs after old school photographers had enough of the 4/3 system with its crap crop factor of 2. Main reason shallower DOF afforded by larger sensors.

2) The nominal distance to subject is usually large enough to render it imperceptible. We're not talking close-up portrait with blurry daisies in the background. Also, if the distance is small enough to show the effect, often it doesn't matter if the background is out. Like in an LPC system.

And regardless, it seems unlikely that the industry is choosing higher f-upped lenses because they fear shallower FOV's.

So I would say although there are differents emphasises and constraints on each discipline, the lens design concerns generally follow the same vector.

Avatar

Nick Ames

In reply to Paul Galburt | 02/23/17 01:11am

Well noted Paul. Coming from a photographic background, and now learning surveillance technology, it is often hard to grasp concepts that seem to be turned upside down. I try to look at it as a completely different concept, or I get into trouble, trying to apply what I thought I previously knew about photography to surveillance cameras/lenses.  I do want to eventually try large sensor (35mm) surveillance cameras.

Avatar

Ng Choy Mei

IPVMU Certified | 05/09/18 11:36am

Seems that varifocal lens is more popular and flexible.

Avatar

David Johnson

05/09/18 05:45pm

Good points all.  I've often found that Optics knowledge is missing or downplayed amongst IT professionals moving into the surveillance realm.  Had one instructor claim that any adjustment necessary could be made with the cameras setup software.  As Charlie Pierce used to say 'We're gathering light first and foremost'.

 

Avatar

Brian Rhodes

IPVMU Certified | In reply to David Johnson | 05/09/18 05:54pm

Charlie Pierce is a legend!  We did an interview with him a few years ago. See: Charlie Pierce: How Video Surveillance / CCTV Has Changed

Also, Charlie likes to give hugs.  (He is a genuinely nice person)

Chin Liang Benjamin Lee

IPVMU Certified | 05/13/18 06:16pm

During previous installation, indeed many customers prefers to use vari-focal lenses due to the reasons mentioned above...nice sharing.

  • customers may want to increase ppf for certain situations and/or increase area of view depending on their perceived need
  • varifocal to allow our installers more freedom to adjust the fov/focal length to meet the customer preference

Charng Haw Guo

IPVMU Certified | 10/31/18 12:00pm

Simple yet easy to missed.

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

Last Chance - Camera Course Winter 2020 on Jan 30, 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...
Vivotek Favorability Report 2019 on Jan 29, 2019
Taiwanese video surveillance manufacturers, even relatively large ones like Vivotek, have lost ground in the PRC-China-driven race to the bottom....
Hanwha Techwin Favorability Results 2019 on Jan 31, 2019
Hanwha Techwin's favorability results surged, in IPVM's 2019 study, going from barely neutral in 2016 to strongly net positive, as the results...
Arecont Favorability Results 2019 on Apr 22, 2019
Arecont's net negativity remained the same in IPVM's 2019 integrator study, though integrator's feeling became relatively more neutral compared to...
Lens Focal Length Tutorial on Jul 10, 2019
3mm, 6mm, 2.8 - 9mm, 5 - 50mm, etc. Camera specifications often list lens lengths but what do they mean? These metrics are important in...
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...
Integrated IR Camera Usage Statistics 2019 on Oct 21, 2019
Virtually every IP camera now comes with integrated IR but how many actually make use of IR or choose 'super' low light cameras without IR? In...

Most Recent Industry Reports

Favorite Video Analytic Manufacturers 2020 on Feb 25, 2020
Video analytics is now as hot as ever, driven by the excitement of advancing deep learning offers. But what are actually integrator's...
Latest London Police Facial Recognition Suffers Serious Issues on Feb 24, 2020
On February 20, IPVM visited another live face rec deployment by London police, but this time the system was thwarted by technical problems and...
Masks Cause Major Facial Recognition Problems on Feb 24, 2020
Coronavirus is spurring an increase in the use of medical masks, which new IPVM test results show cause major problems for facial recognition...
Every VMS Will Become a VSaaS on Feb 21, 2020
VMS is ending. Soon every VMS will be a VSaaS. Competitive dynamics will be redrawn. What does this mean? VMS Historically...
Video Surveillance 101 Course - Last Chance on Feb 20, 2020
This is the last chance to join IPVM's first Video Surveillance 101 course, designed to help those new to the industry to quickly understand the...
Vulnerability Directory For Access Credentials on Feb 20, 2020
Knowing which access credentials are insecure can be difficult to see, especially because most look and feel the same. Even insecure 125 kHz...
AI/Smart Camera Tutorial on Feb 20, 2020
Cameras with video analytics, sometimes called 'Smart' camera or 'AI' cameras, etc. are one of the most promising growth areas of video...
China Manufacturer Suffers Coronavirus Scare on Feb 20, 2020
Uniview suffered a significant health scare last week after one of its employees reported a fever and initially tested positive for coronavirus....
Cheap Camera Problems at Night on Feb 19, 2020
Cheap cameras generally have problems at night, despite the common perception that integrated IR makes cameras mostly the same, according to new...

What IPVM Is

The world's leading authority on video surveillance, with 200,000+ visits monthly.

  • Articles on cameras, video analytics, VMS, and trends
  • Tests showing actual performance and problems
  • Courses in surveillance, access control, etc
  • Camera Calculator for designing systems

Dedicated To Independence

We're dedicated to staying independent and objective. We're the only industry source to refuse any and all advertisements, sponsorship, and consulting from manufacturers. Why?