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)

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?

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...

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?

...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.

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.

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.

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.

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.

Seems that varifocal lens is more popular and flexible.

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'.

 

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)

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

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

Bosch Budget 3000i Cameras Tested on Dec 05, 2019
Bosch has long had a hole in its lineup for, as it describes, "competitively-priced cameras". Now, Bosch has released its 3000i series cameras...
AVTech ~$70 IP Cameras Tested Vs Dahua and Hikvision on Dec 04, 2019
Taiwanese manufacturer Avtech is taking direct aim at low cost leaders Dahua and Hikvision with ~$70 starlight and white light illuminator...
Budget Covert Cameras Tested on Nov 26, 2019
Covert cameras under $100 are widely available online but are they any good? To see how these models really work in the real world, we bought...
Vunetrix Health Monitoring Company Profile on Nov 26, 2019
Vunetrix boasts that they make the integrators the 'HERO' by using Vunetrix's monitoring. We spoke to Vunetrix to better understand their...
Top 2020 Trend - AI Analytics on Nov 22, 2019
170+ Integrators answered: What do you think will be the top industry trend in 2020? Why? For the 4th year in a row, AI/video analytics was...
Axis "Best Of The Best" 4K Camera Tested (Q1798-LE) on Nov 21, 2019
Axis has released their "best of the best" Q1798-LE bullet camera, touting "4K without compromise" with a large Micro 4/3" image sensor, custom...
Hikvision Dual Lens Face Recognition Camera Tested on Nov 19, 2019
Hikvision's Dual Lens Facial Recognition camera, claims that it "adopts advanced deep learning algorithm and powerful GPU to realize instant face...
Top Manufacturers Gaining and Losing 2019 on Nov 18, 2019
2019 has been an explosive year for video surveillance, with the world's two largest manufacturers, Dahua and Hikvision, being sanctioned for human...
ADT Stock Surges - "Leading The Commercial Space" on Nov 15, 2019
Don't call it comeback... but maybe call it a commercial provider. ADT, whose stock dropped by as much as 2/3rds since IPOing in 2018, has now...
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...

Most Recent Industry Reports

Disruptor Wyze Releases Undisruptive Smartlock on Dec 06, 2019
While Wyze has disrupted the consumer IP camera market with ~$20 cameras, its entrance into smart locks is entirely undisruptive. We have...
Bosch Budget 3000i Cameras Tested on Dec 05, 2019
Bosch has long had a hole in its lineup for, as it describes, "competitively-priced cameras". Now, Bosch has released its 3000i series cameras...
Anixter Resisting Takeover From Competitor on Dec 05, 2019
Mega distributor Anixter is going to be acquired but by whom? Initially, Anixter planned to go private, being bought by a private equity firm....
Security Sales Course 2020 - Last Chance Save $50 on Dec 05, 2019
This sales course is customized for the current needs and challenges specific to professionals selling video surveillance and access control...
Ireland National Children's Hospital Chooses Hikvision End-to-End With Facial Recognition on Dec 05, 2019
The world's most expensive hospital project ever, the New Children's Hospital in Ireland, has chosen an all-Hikvision surveillance system including...
AVTech ~$70 IP Cameras Tested Vs Dahua and Hikvision on Dec 04, 2019
Taiwanese manufacturer Avtech is taking direct aim at low cost leaders Dahua and Hikvision with ~$70 starlight and white light illuminator...
Ultinous European Analytics Startup Company Profile on Dec 04, 2019
European analytics-startup Ultinous pitches customers to "Have your own video analysis service!" We spoke to Ultinous to better understand their...
Access Startup Multi-Mount Aims To Streamline Reader Installs on Dec 03, 2019
Startup Multi-Mount claims it makes installing access readers 'Fast', 'Secure,' and fit 'any size frame.' The company states its bracket 'fits most...
Resideo CEO To Step Down on Dec 03, 2019
Resideo's CEO, Mike Nefkins, is stepping down, just 18 months after being brought in to lead the now plagued spin-out. Inside this note, we...
Arcules CEO Retracts False GDPR Claim + Dahua and Milestone Claims Examined on Dec 03, 2019
Arcules CEO has retracted a false claim about his organization being a "fully compliant GDPR company" after IPVM reporting (Arcules CEO Threatens...