Varifocal vs Fixed Focal LensBy John Honovich, Published May 29, 2014, 12:00am EDT
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.
Integrators use varifocal lenses by a 2:1 margin over fixed focal lenses:
Indeed, the majority of integrators almost always use varifocal lenses as this chart demonstrates:
However, a handful of integrators rarely use varifocal lenses as shown above in the small bump on the 10 to 30% range.
Indeed, for non-integrators, such as the home and DIY market, fixed focal lenses are generally the only lens type offered. As such, including those segments (home / DIY), the percentage of all cameras using fixed focal lenses is likely ~50%.
Why Varifocal vs Fixed Focal
The most common reason to use varifocal lenses, cited by integrators, was to optimize the FoV for the end user's preference:
- "Varifocal is 90+% of our deployments due to the lens allowing the camera to have the view the client wants"
- "We have found that customers will often take advantage of the varifocal to increase ppf for certain situations and/or increase area of view and sacrifice ppf depending on their perceived need."
- "This adds flexibility to the end user who often think they want to see a particular field of view, but then after seeing the live image often want to either widen or tighten the field of view."
- "We use primarily varifocal to allow our installers more freedom to adjust the fov/focal length to meet the customer preference"
- "To accommodate the field requirements in support of installation changes made due to project manager, field technician, and/or customer."
- "We want the flexibility for the technicians onsite to be able to change the parameters of the view if the customer changes their mind about what they deem to be important to them."
Since many end users change their mind after about how wide a FoV they want, after the camera is installed, varifocal enables integrators to quickly meet this.
However, one integrator offered a different approach to meet this, without using varifocal lenses, explaining that, "We stock different focal length cameras and just use whichever one is required." To the contrary, as another integrator noted, varifocal "speeds in service and installation when we dont need to stock a series of lenses."
For fixed focal lenses, the clear number #1 reason was lower cost, not simply for the lens itself, but because fixed focal lens cameras are typically less expensive, less powerful cameras overall. Integrated noted:
- "The only reason we go fixed is because of cost."
- "We use fixed focal lenses when we need more cost effective solution."
- "Customers love adjustments. Fixed when cost is involved."
- "if cost is a factor and you know it just a relatively wide view, then we are more likely to select fixed."
However, they do come with limitations, as one integrator explained, "I would use higher percentage of fixed but they typically have worse quality video, for example we like to install WDR & the fixed aren't always WDR you have to go to higher end model (varifocal) to also get WDR." Note, this is not because fixed cameras cannot technically support WDR (indeed WDR is a sensor / encoder functionality, not lens) but typically fixed cameras are optimized for lowest cost, stripping features like true WDR.
Fixed focal lenses are not lower quality than varifocal lenses. Indeed, fixed focal lenses reduce the risk of cameras being out of focus (but generally do not eliminate it as fixed focal lenses typically come with a fine focus that can be out of focus). However, manufacturers typically package fixed focal lenses with simple cameras, often with smaller imagers and less features.
Integrators noted a number of specialized applications where fixed lenses are the norm - such as fisheye / panoramics, thermal and super high resolution cameras.
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