Quick CCTV Lens Facts
If you are using a C/CS mount security camera or maybe a miniature or board camera; then you are most likely aware that you will also need a CCTV lens to accompany your camera. Knowing that you need a lens and knowing what to look for in a lens, are two separate things. To help with this distinction, we will look at a few basic facts about CCTV lenses, and why they are helpful when choosing a lens.
Varifocal vs Fixed Focal Length
A varifocal CCTV lens has the capability to have its focal length adjusted in a certain range. For example if you have a 9mm – 22mm varifocal CCTV lens; this means that you can manually adjust your focal length anywhere from 9mm up to 22mm. This allows for a bit of versatility, and lets you get however narrow or wide a camera view you might need within this range.
A fixed focal lens is exactly the opposite of a varifocal lens. Instead of having a range of focal lengths to choose from, you only get a fixed length. For example if you have a 4.3mm fixed focal lens; then this means that your focal length will always be 4.3mm, and it cannot be adjusted to a different length.
What is focal length?
To make this as simplistic as possible, the focal length on your CCTV lens is basically a correlation to how zoomed in or out you are; or basically how wide or narrow your camera view is. The smaller your focal length, the wider the angle of view will be; whereas if you have a large focal length, then you will have a narrower field of view. For example a 2.8mm lens is much wider than a 25mm lens.
Manual vs Electronic Zoom
If your CCTV lens has a zoom capability; then it is a varifocal CCTV lens. When it comes to manual versus electronic zooms, the distinction is simple. If you have a manual adjustment; then you physically have to adjust your focal length (zoom). If the camera has an electronic zoom, you can then use a third party controller to zoom in or out.
F-Stop
The F-Stop rating of your CCTV lens is how well it will work in low light conditions. The lower the f-stop rating; then the better it will work in low light, and the higher the rating equals a worse low light capability. This rating is usually represented as an F followed by a period and then the rating number (for example: F.1.2).
Mounting
A final tip that should be known when looking for a CCTV lens, is to know what type lens mount you will be using. Basically you will need to check if your security camera is a C mount / CS mount / M12 / or M9 type mounting system. Knowing this will help narrow down your selection of lenses or adapters you might need.
Christian M Gillman has worked in the surveillance industry for over 6 years. Subscribe to our monthly newsletter, learn more about surveillance, and find great products at http://www.cu1.com
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