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Security Camera Blog

field of vision security cameras Utah

Lenses And Field Of View

Most cameras purchased today have built in lenses which can even make it harder in determining if a camera is a good price or not. The type of lens will determine the Field of View for the camera.

There are many types of lenses and they play a major role in the cost of a camera. While you want to make sure that you get a good camera and lens for what you need, you don’t want to pay for something that you won’t need or use.

The field of view is a reference to how wide or narrow a camera shot is. Fixed lens cameras have a fixed field of view. They come preset and they don’t change. The smaller the number of the lens, the wider the field of view. A standard fixed lens in the industry is known as a 3.6 mm lens. This lens gives a 90-degree field of view. This is about perfect for most applications. I prefer a 2.8 mm lens, which gives about a 110-degree field of view. I believe it works better in tight spaces, doesn’t have as much of a blind spot right under the camera, and provides the customer with a greater field of view which they almost always want. A 2.8mm lens camera, gives wall to wall coverage by putting it in the corner of a room.

A varifocal lens camera, or VF camera, has a variable field of view that can be adjusted manually by little screws on the camera. This type of camera can be placed on a ceiling and be zoomed in tight on a cash register drawer. In the last couple of years, motorized VF cameras have become popular and cost effective. These cameras have a motorized VF lens that allows people to adjust the view of the camera remotely through the software. The drawback to this type of camera is that it can also get out of focus electronically as well. A power outage or surge might bring the camera up in a different focus than what it was at before. The camera would remain out of focus until someone sees it and fixes it.

Varifocal lenses come in a variety of ranges. The most common range is 2.8-12mm. For almost all inside and many outside applications, the 2.8-12mm range camera will fit the criteria needed. Sometimes however, there is a need to be able to see a little further. If a clear line of sight exists, the right lens can get you closer. One of the camera types that I love to bid on our installs is an HD 1080P Bullet camera with a 5-50mm VF Lens.

I use this type of camera to set up for license plate shots on vehicles that are farther away. By putting one of these cameras on the building and focusing it on the exit from the parking lot to the street, we can read the license plate on vehicles as they leave. The use of varifocal cameras can make a huge difference in laying out a camera installation. They allow us to put cameras further from the area we want to see and allow the zoom to bring us close at a more advantageous angle.

Moving the opposite direction from the varifocal, I am often asked about fish eye lenses. They are lenses that have a 360-degree fixed field of view. They used to be used a lot in small spaces like behind the counter of a convenience store. Recently, many companies have developed software that will take the view of a High Definition fish eye lens camera and break it our into four different pictures. This makes it possible to put a camera on the ceiling in a small room and have four pictures from it. Although it does have a place, I personally don’t find a lot of situations where this type of camera gives me a better layout than two 2.8mm cameras on opposite corners. It is tricky to find an area where I need a complete 360-degree view. The cost for one of these specialty cameras would normally be about the same as two of the 2.8mm cameras, so I believe the two cameras to be a better solution.

At Dixon Security we are security system experts. Call us at 801-455-0413 for a FREE on-site evaluation of your video surveillance needs.