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How does motion detection work?

Published by Marie on June 11, 2015 2:28 PM

Motion detection is an important tool for securing your business or building. It alerts you when someone is on your property that isn't authorized. Understanding how this technology helps you set up better motion detection regions and alerts, but do you actually know how motion detection works?

To understand motion detection, you first need to understand how a camera works. Inside the camera is an image sensor, which the camera lens directs light to - when light hits the image sensor each individual pixel records how much light it's getting. That pattern of light and dark areas on the pixels becomes the complete video image you see. You can read a more in-depth explanation of image sensors here.

When you set up motion detection, you select a region or area to monitor, say a doorway. The way it works is to compare sequential images from your video and if enough of the pixels have changed between those frames, the camera software determines something moved and sends you an alert.

How "enough" change is determined depends on the sensitivity level or percentage level settings you put on your motion detection.

The sensitivity level looks at the changing light/dark levels in the pixels. Higher sensitivity will pick up on more changes while lower sensitivity will require a large level of change, such as the lights going on in a dark room, to set off the alerts. Percentage, on the other hand, looks to the percentage of pixels that have registered a change. If you are monitoring a door, setting the percentage at 50% will alert you when something large walks into the room, such as a person, but ignore something smaller.

Getting the best balance in your motion detection settings to prevent too many false alerts may take some time. While setting up your camera you can test the motion detection by having someone walk in the motion detection region and adjust the settings as needed. It may take some time, but the effort is well worth it when you're notified of a break-in at your store or vandals prowling the parking lot.


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