Lens Types
There are two main CCTV camera lens types: fixed lens (aka. monofocal lens) and varifocal lens (these include motorised lenses).
A CCTV security camera that has a fixed lens is permanently set, meaning that its angle of view, focal length and level of zoom cannot be changed.
PTZ Cameras are an example of a popular camera form that include a varifocal, motorised lens.
On the other hand, a CCTV camera with a varifocal lens will allow users to adjust the camera’s focal length, and consequently its field of view and level of zoom. This means that the lens can zoom in to capture a close view from a long distance (reducing the Field of View, but providing a clearer image of details such as licence plates, or perpetrators’ faces), or zoom out to capture a wide area (increasing the Field of View).
Motorised vs Manual Zoom Lenses
Most varifocal CCTV security cameras are equipped with motorised zoom lenses, however some varifocal cameras are manual. This means that they must be manually adjusted to change the camera’s focal length.
Business Application:
For business applications, it is recommended that you opt for a motorised zoom lens if your budget allows. This lens type enables the camera to automatically adjust its focal length, resulting in clear and auto-focused footage.
Motorised lenses are unlikely to lose focus due to the effect of natural factors such as wind and temperature (causing shrinkage, and expansion of the camera), however, manually adjusted varifocal lenses are more susceptible to this problem – potentially leaving an unattended business’ security systems vulnerable.
Motorised lenses also take the hassle out of manually adjusting the camera yourself, allowing you to control the camera remotely from a smartphone app or web-interface. This means that you can adjust your camera’s focal length, and viewing angle from anywhere, at any time – with the click of a button, or rather a touch of your screen!
Home Application:
In a home setting a manual varifocal lens or even a high resolution fixed lens CCTV camera is often the more cost effective and appropriate option. Our customers tend to choose fixed lens cameras for domestic installations due to the higher cost of varifocal products.
A high resolution camera of 4MP or more will give homeowners the ability to capture information such as facial details and licence place numbers. While a motorised varifocal lens would use its zoom function to capture this important information, the footage of a high resolution fixed camera can be ‘zoomed’ in on after the fact to capture the same vital details.
The only difference then, would be that the field of view of a CCTV camera with a fixed lens cannot easily be adjusted once the camera has been installed (the camera would have to be reinstalled in a different position). However, if the cameras have been placed by a professional, and their field of view has been checked to ensure that optimal coverage is available this shouldn’t be an issue.
That being said, it is important to take into consideration that this is where manual varifocal lenses pose an advantage over fixed CCTV cameras. If a manual varifocal camera has not been installed to its best viewing ability, the lens can easily be adjusted, without the fuss of having to reinstall the entire camera system.
If using a fixed lens camera or manual varifocal camera to monitor the exterior of your home – it is advised that you install/adjust a combination of lager focal length and smaller focal length cameras. This is so that important details, as well as wide-angle views can be captured. We will further discuss focal length in the next section.
| Lens Type | Features | Suitable Usage |
|---|---|---|
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Fixed Lens |
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Varifocal Lens |
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Lens Control View as Determined by Focal Length
The focal length refers to the gap between the lens and the image sensor when the camera’s subject is in focus. This determines how far a camera can see and is often stated in millimetres. It is important to note that the larger the size of the lens, for example 4mm, the narrower and more ‘zoomed in’ the camera’s field of view will be. If the lens is a smaller size, for example 2.8mm, the CCTV camera will be able to capture wider areas.
Fixed Lens Camera:
| Lens Focal Length | Horizontal Field of View |
|---|---|
|
2.8mm |
90° |
|
4mm |
60° |
|
6mm |
45° |
|
12mm |
25° |
We most commonly use the 2.8 mm focal length for domestic installations. Customers are generally trying to cover their entire property with 4-6 cameras so the wider field of view is required.
Varifocal Lens Camera:
A varifocal camera will allow you to adjust between its top and bottom view field of view limits. For example, many varifocal cameras are able to move between 2.8 – 12mm.
Here at Jim’s Security we have a wide range of CCTV packages starting at $1495 and offer professional installation of customer supplied CCTV systems from just $150 per camera. To find out more, visit our CCTV & Camera Systems page. Or to learn more about the different features and components of CCTV systems and security cameras take a look at our CCTV and Security Camera Buyers Guide.
We are also readily available to help answer any questions or queries you may have about finding a security system tailored to the specific requirements of your home or business and lifestyle. Contact us on 131 546 or book a free onsite quote online.
