By Damion Dick
In our “de-mystifying CCTV specs for DIYers” series, we take a look at the differences in common lens types… the Fixed and Varifocal (or Zoom) lens.
*Please note that a Zoom Lens is not a PTZ as that is Pan, Tilt, AND Zoom.
Ok so let’s jump right in.
Fixed Lens:
These cameras come with a pre-configured lens which gives you a fixed field of view. With few moving parts, fixed view cameras provide a simple set up.
The numbers 2.8mm, 3.6mm, etc., are mainly describing the field of view with the higher the number meaning the narrower or more focused the Field Of View (FOV).
Also depending on the manufacturer your field of view for the same lens type may vary, for example, a Hikvision 2.8mm camera may have a FOV of 109 degrees and an Axis 2.8mm camera may have a FOV of 106 degrees.
Varifocal Lens:
Varifocal cameras allow you to adjust the field of view until you have the desired result.
Unlike a pan tilt zoom models; this adaptability is used at the installation phase.
Once your field of view is set, it stays the same, until it is adjusted later on.
To make installation a little easier, some manufacturers have created varifocal cameras with remote zoom and focus (aka Motorized lens).
Motorized zoom lens enables you to make small adjustments to your field of view after installation.
So, when is the best time to use each?
Use a fixed lens if:
- Budget is small. These cameras tend to be cheaper than their Varifocal counterparts and usually come in about $90 to $160 USD for IP and less for the HD cameras.
- If you just need a general view. Please note as much as the resolution might be 4K (8MP), a fixed lens of 2.8mm should not be used to read License plates, at any distance. It is much better suited for a backyard or a parking lot.
- You want a less complicated install. These are the popular choice for DIYers as they just mount it and point it in the general direction and that’s it.
Use a varifocal lens if:
- If you are unsure about the FOV required.
- You may have a narrow space or a distant object and may be unsure about what lens would exactly fit your purpose. Due to their adjustability you can find the sweet spot.
- You have a bigger budget or very specific requirements.
Ok then. You should now know t the difference between fixed and varifocal cameras.
Knowing that fixed lenses are useful for budget conscious installations which require an overview but for sites requiring precise monitoring, a varifocal would be a better choice.
Hopefully this helps you to understand the difference between fixed and varifocal lens, though they may look the same, and also, help you along your DIY or Pro journey to understanding CCTV cameras.
If you or someone you know need expert advice, then share this article with them.
Also head over to my YouTube channel for more content like this, don’t forget to like and subscribe.
HIRE US as well for a Project or a Consultation –>CLICK HERE<–
Follow us: