Progressive scan images provide the clearest surveillance footage.

Progressive scan images are recorded and displayed as a single field which runs from the top to the bottom of the screen, line by line.

Analogue cameras and some network cameras provide interlaced images instead. This means that alternate lines of the image are stored in two separate fields, which are slightly out of sync.

Playing back interlaced video on a computer screen, which uses progressive scan, results in a blurring effect around fast moving objects.