Varifocal vs Fixed Focal Lens

Author: 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.

******** ******* ********* *** ***** ***** **** ** *** ** the **** *********** ********* ** ***** ************.

**** * ***** ***** ****, *** ***** ** **** (***) of *** ****** *** *** ** ******* ****** *** **** is *******. ** ********, ********* ****** ***** *** ********* ********** of *** *** ****** ** ********* * ******* ** *** lens / ******.

*** ***** *** ** **** **** *** ***?

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

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

*********** *** ********* ****** ** * *:* ****** **** ***** focal ******:

 ******, *** ******** ** *********** ****** ****** *** ********* ****** as **** ***** ************:

*******, * ******* ** *********** ****** *** ********* ****** ** shown ***** ** *** ***** **** ** *** ** ** 30% *****.

******, *** ***-***********, **** ** *** **** *** *** ******, fixed ***** ****** *** ********* *** **** **** **** *******. As ****, ********* ***** ******** (**** / ***), *** ********** of *** ******* ***** ***** ***** ****** ** ****** ~**%.

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

***********

*** **** ****** ****** ** *** ********* ******, ***** ** integrators, *** ** ******** *** *** *** *** *** ****'* **********:

  • "********* ** **+% ** *** *********** *** ** *** **** allowing *** ****** ** **** *** **** *** ****** *****"
  • "** **** ***** **** ********* **** ***** **** ********* ** the ********* ** ************** ******* ********** ***/** ******** **** ** **** *** ********************* ** ***** ********* ****."
  • "**** **** *********** ** *** *** **** *** ***** ***** they **** ** *** * ********** ***** ** ****, *** then ***** ****** *** **** ***** ***** **** ** ****** widen ** ******* *** ***** ** ****."
  • "** *** ********* ********* ** ***** *** ********** **** ******* to ****** ******/***** ****** ** **** *** ******** **********"
  • "** *********** *** ***** ************ ** ******* ** ************ ******* made *** ** ******* *******, ***** **********, ***/** ********."
  • "** **** *** *********** *** *** *********** ****** ** ** able ** ****** *** ********** ** *** **** ** *** customer ******* ***** **** ***** **** **** **** ** ** important ** ****."

***** **** *** ***** ****** ***** **** ***** ***** *** wide * *** **** ****, ***** *** ****** ** *********, varifocal ******* *********** ** ******* **** ****.

*******, *** ********** ******* * ********* ******** ** **** ****, without ***** ********* ******, ********** ****, "** ***** ********* ***** ****** cameras *** **** *** ********* *** ** ********." ** *** contrary, ** ******* ********** *****, ********* "****** ** ******* *** ************ **** ********** ** ***** * ****** ** ******."

****

*** ***** ***** ******, *** ***** ****** #* ****** *** lower ****, *** ****** *** *** **** ******, *** ******* fixed ***** **** ******* *** ********* **** *********, **** ******** cameras *******. ********** *****:

  • "*** **** ****** ** ** ***** ** ******* ** ****."
  • "** *** ***** ***** ****** **** ** **** **** **** effective ********."
  • "********* **** ***********. ***** **** **** ** ********."
  • "** **** ** * ****** *** *** **** ** **** a ********** **** ****, **** ** *** **** ****** ** select *****."

*******, **** ** **** **** ***********, ** *** ********** *********, "* ***** ********* ********** ** ***** *** **** ********* **** ***** ******* video, *** ******* ** **** ** ******* *** & *** fixed ****'* ****** *** *** **** ** ** ** ****** end ***** (*********) ** **** *** ***." ****, **** ** not ******* ***** ******* ****** *********** ******* *** (****** *** is * ****** / ******* *************, *** ****) *** ********* fixed ******* *** ********* *** ****** ****, ********* ******** **** true ***.

***** ***** ****** *** ******** ******* **** ********* ******. ******, ***** ***** ****** ****** the **** ** ******* ***** *** ** ***** (*** ********* do *** ********* ** ** ***** ***** ****** ********* **** with * **** ***** **** *** ** *** ** *****). However, ************* ********* ******* ***** ***** ****** **** ****** *******, often **** ******* ******* ***************.

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

*********** ***** * ****** ** *********** ************ ***** ***** ****** are *** **** - **** ** ******* /**********, ******* *** ***** **** ********** *******.

Comments (12)

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
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

Mobotix Releases 'Move' Into 21st Century on Jun 20, 2018
For years, Mobotix stood resolutely against, well, every other manufacturer, selling it as a virtue: MOBOTIX equipment is designed with no...
The Dumb Ones: PSA's Bozeman On Cybersecurity on Jun 15, 2018
The smart ones are the hundred people who flew to Denver and spent $500+ on a 1.5-day conference featuring Dahua as a 'cyber responsible partner',...
Avigilon H4 Multi-Sensor Adds 32MP, H.265, Analytics on Jun 13, 2018
Avigilon has announced the H4 Multisensor, the successor to their repositionable multi imager line, adding features like H.265, integrated IR,...
Introducing Effective PPF (ePPF) - Improving Video Surveillance Designs on Jun 11, 2018
Pixel density (PPF / PPM) is the best metric the industry has to define and project video quality. It allows simple communication of estimated...
Hanwha Low-Cost 4MP Camera Tested (QNV-7010R) on Jun 11, 2018
4MP usage is increasing noticeably, as IPVM 2018 resolution statistics show. And low-cost, fixed focal cameras, are popular for budget...
Worst Features for Camera Installation (Statistics) on Jun 07, 2018
4 clear worst features for installing were identified by 140+ integrator respondents to: What feature(s) make a camera hard to install? The...
Top Features For Easy Camera Installation (Statistics) on Jun 05, 2018
Camera installation is the most fundamental and common task for video security technicians. Because of this, camera manufacturers market their...
Stats: IP Camera Dead On Arrival (DOA) Decline, Near Zero on Jun 01, 2018
New IPVM integrator statistics show that IP camera DoA rates have declined with zero dead on arrival units for many integrators and effectively...
Stats: Upgrading Cameras Far More Common Than Replacing Failed Cameras on May 30, 2018
The old saying "If It Ain't Broke, Don't Fix It" does not apply here. New IPVM statistics show that 60% of cameras that are replaced still work but...
Installing Box Cameras Indoors Tutorial on May 22, 2018
This tutorial starts our physical installation for video surveillance series, starting with Box Cameras, one of the oldest and most basic types....

Most Recent Industry Reports

IFSEC Show Report Day 2 Report on Jun 20, 2018
IPVM is live from London reporting on the IFSEC show. The Chinese have taken over the UK, centered on Hikvision, flanked by Dahua, Huawei and a...
Mobotix Releases 'Move' Into 21st Century on Jun 20, 2018
For years, Mobotix stood resolutely against, well, every other manufacturer, selling it as a virtue: MOBOTIX equipment is designed with no...
Cybersecurity Startup VDOO Disclosing 10 Manufacturer Vulnerabilities Starting With Axis And Foscam on Jun 20, 2018
Cybersecurity startup VDOO has uncovered significant vulnerabilities in Axis cameras along with many others not yet disclosed. In this report, we...
July 2018 IP Networking Course on Jun 19, 2018
The last chance to save $50 on registration is this Thursday, June 21st. Register now and save. This is the only networking course designed...
Axis Guardian - Cloud VMS And Alarm Monitoring - Released on Jun 19, 2018
Axis has struggled to deliver a cloud-based managed service video platform. Video service providers have utilized AVHS for over a decade, and have...
IPVM Vulnerability Scanner Released on Jun 18, 2018
IPVM is proud to announce video surveillance's first and only cybersecurity vulnerability scanner. This tool allows quickly and simply...
Hikvision Corrects False Cybersecurity Announcement on Jun 18, 2018
Hikvision has corrected a false cybersecurity announcement that claimed a British government-sponsored program endorsed the cybersecurity of...
The Dumb Ones: PSA's Bozeman On Cybersecurity on Jun 15, 2018
The smart ones are the hundred people who flew to Denver and spent $500+ on a 1.5-day conference featuring Dahua as a 'cyber responsible partner',...
Amazon Ring Launches $10 Monthly Professional Alarm Monitoring on Jun 15, 2018
Amazon's Ring has announced an alarm system with 24/7 professional alarm monitoring for $10 per month, a fraction of the $30+ per month traditional...
Axis Releases First New Access Controller In 5 Years (A1601) on Jun 15, 2018
It has been 5 years since Axis 2013 entry in the physical access control market, with the A1001 (IPVM test). Now, Axis has released its second...

The world's leading video surveillance information source, IPVM provides the best reporting, testing and training for 10,000+ members globally. Dedicated to independent and objective information, we uniquely refuse any and all advertisements, sponsorship and consulting from manufacturers.

About | FAQ | Contact