What is Digital Zoom on Surveillance Cameras?

Digital zoom does not utilize moving lens elements like optical zoom does. Instead, it ‘crops’ the desired portion of the image to take up the entire frame size on the display. Therefore, unlike optical zoom, no more detail is gained from digitally zooming. Instead, existing details in the image are simply enlarged, and effective resolution quickly drops when using digital zoom as the full sensor is not being utilized. This can result in a very poor looking image with lower/mid resolution sensors, or poor looking images in extreme cases of digital zoom on HD and higher resolution sensors.

However on sensors with resolutions of 3MP or higher, digital zoom can be a helpful tool to see the full detail that the sensor is capturing, which is often not fully realized on playback monitors that tend to be HD/1080p resolution (which is only 2MP).