Maximize Surveillance Range: Comparing 30x, 36x, 44x, and 55x Optical Zoom Lenses
A basic surveillance camera can see anywhere from 0-250 feet at night, depending on the infrared (IR) sensor, camera model and lens. Law enforcement video surveillance cameras used on The RATT can see in complete darkness (0 Lux) and have much longer ranges (over 1,300 feet) when equipped with a special IR or laser.
No matter what type of camera you have, if you can’t zoom into an image, your footage may often be of little use. Being able to zoom in and see details is crucial in many surveillance situations to record things like the subject’s description, facial features and even license plates.
To do this successfully, you will need to have the right specs on your optical lens and surveillance camera. Otherwise, you may end up with a blurry, grainy image. This is especially important for PTZ cameras, where zoom performance directly determines how far you can identify a subject from an elevated position.
Want to ensure this doesn’t happen? If so, read on to find out the difference between a 30x, 36x, 44x, and 55x optical zoom lens, as well as the other factors behind zoom image quality that you need to consider.
How an Optical Zoom Lens Works
Optical lenses zoom by moving the camera sensor further away from the lens, effectively giving the sensor a smaller (and more close up) field of vision. The amount by which you can do this depends on the focal length your camera is capable of.
Where things get tricky is with the optical zoom ratio.
Optical Zoom Numbers Explained
When shopping for a camera, you probably want to know how many feet an optical zoom lens will be able to “see” and be done; however, it’s not that simple.
To make an informed decision, you’ll need to know a little bit about optical zoom ratios and how they interplay with other camera specs.
To start with, the zoom ratio figure (such as 30x, 36x, 44x, etc) is simply the difference between the shortest and the longest focal point of a lens. To get to the ratio, all one has to do is divide the maximum focal length of a lens by its minimum focal length.
For instance, say you are looking at a camera with a lens that features a 150-600mm focal length. The zoom ratio of this lens would be 600÷150=4x.
Why You Need to Focus on Focal Length
When looking at the zoom ratio on a lens, it is very important that you factor in the focal length.
As we mentioned above, the minimum and the maximum focal length on a lens determines the zoom ratio. Because of this, some cameras with a higher zoom ratio could actually have a weaker magnification ability.
Let’s explain.
If you have a wide-angle lens with a focal range of 15mm-150mm, this will give you a 10x zoom factor. Now, let’s compare this to a non-wide angle lens with a 50mm to 200mm focal range.
The second lens will have a zoom ratio of 4x, which should be weaker than 10x; however, the 10x lens is the one with weaker zoom capacity, because its maximum focal length is 50mm less.
If this is washing over your head; think of it like this.
The more of a wide-angle a lens you have, the less punch its zoom ratio will actually pack; however, don’t think that wide-angled lenses equal weak zooming powerful—they can actually give you more bang for your zoom ratio if they have a high resolution (more on this below).
So What Zoom Ratio Do I Need for How Many Feet?
If you are setting up a mobile surveillance unit (MSU), chances are you want the quick and dirty on what specs will give you how many feet of zoom power.
Because zoom ratios can be misleading, there is no set relationship between what zoom ratio is required for how many feet. However, a rough rule of thumb is that with a 4x zoom ratio you can ID someone 100 feet away.
Following on from that, for identifying someone at 200 feet, you’ll need a 20x zoom ratio, and a 30x zoom ratio for 250ft.
Although zoom ratios can give you an idea of what lens will suit your needs, there are some other factors that play into your zoom quality.
Optical Zoom Specs Can Be Deceiving
When comparing optical zoom lenses, do not forget that zoom ratio specs can be deceiving, and aren’t the end-all be-all of zoom capabilities or zoomed image quality.
While optical zoom ratios can give you an idea of the zoom on a lens, there are two other main factors you need to keep in mind. One of these is the wide-angle factor, as we mentioned above. The other is resolution.
Let’s take a look.
The Wide-Angle Factor
Wide-angle lenses are typically considered to be any lens with a minimum focal length of less than 50mm. Because of their low minimum focal length, wide-angle cameras will often have higher optical zoom ratios, even though their zoom capability may not be much higher.
Take note, however, that having a wide-angle lens is not a bad thing for surveillance at all. In most surveillance situations, you want to be able to capture as much of the scene as possible, especially if you are monitoring areas using drone surveillance or a telescoping mast.
For agencies that need both wide-area coverage and zoom capability simultaneously, multisensor cameras combine multiple lenses in a single housing for full 360-degree coverage.
How Pixels Play In
Another factor that will impact zoom capability is camera resolution. Cameras with higher resolutions will yield better quality zoomed-in footage.
Because of this, a security camera with a 32x zoom ratio and a high resolution could potentially have similar zoom capabilities as a camera with a 50x zoom ratio with lower resolution.
Higher resolution cameras generate larger video streams, which makes choosing the right video compression critical when streaming over cellular connections.
Do You Need to Elevate Your Surveillance Camera?
If your agency needs a rapid-deploy mobile surveillance solution, you are in the right place. Our mobile surveillance tower, including The RATT, is a field-swappable telescopic mast that goes from vehicle to operational in under ten minutes. All it needs is a 2 inch hitch receiver. No crew, no tools, no delay. If a vehicle mount is not what you need, it also deploys on a tripod, wall mount, or solar surveillance trailer for long-term autonomous coverage.
The cameras compared in this article — Axis, Avigilon, Pelco, Silent Sentinel, and Hanwha — are all available through CTS as an authorized technology partner. Whether you need a 30x PTZ for a parking lot or a 55x long-range imager for a wide open perimeter, we can put the right camera on the right platform for your mission.
