5. Selecting the correct zoom factor
The quality of the video picture depends very much on the zoom factor selected. When selecting a
zoom factor, note these installation tips:
Perception
Large area covered (zoomed out), so no
detailed recognition possible. A 2m tall person
takes up about 5% of the screen height. The
monitored area has a size of about 50m x
40m (WxH). A camera at 30 meters requires
a lens with a focus of f=2.8mm.
Detection
Large area covered (zoomed out), so little
detailed recognition possible. Use of video-
sensors possible. A 2m tall person takes up
about 10% of the screen height. The
monitored area has a size of about 25m x
20m (WxH). A camera at 30 meters requires a
lens with a focus of f=6mm.
Recognition
Small area covered (zoomed in); details can
be recognised. A known person is
recognisable. A 2m tall person takes up about
50% of the screen height. The monitored area
has a size of about 5m x 4m (WxH). A camera
at 30 meters requires a lens with a focus of
f=28mm.
Identification
Small area covered (zoomed in); details can
be recognised very clearly. A 2m tall person
takes up about 120% of the screen height.
The monitored area has a size of about 2.5m
x 2m (WxH). A camera at 30 meters requires
a lens with a focus of f=60mm.
Camera-to-object distance x 4.4
Object width
Use the following formula for calculating the lens focus:
f (focus) =
32
