5 Mega-pixel Vandalproof IR PoE IP Camera
ICA-E5550V
52
“speed limit” of sensitivity (70).
The blue graph on the right side of the image shows how many percent of pixels within the
motion detection region were considered as “currently in motion”. The activity panel itself is a
timeline – for each moment of time you can see the height of the blue bars. You may notice
that at certain moment the tallest bars in the activity graph reached about 25% (a quarter of the
total height in activity panel) – it means, 25% of this motion detection area were filled with
moving pixels at that moment. By visual observation you can also see that the object standing
inside the motion detection region indeed covers about 25% of its size.
What if the object is really small but moves rather fast (gets triggered by the current sensitivity
level)? For example, we want to detect people but not the cat walking in the room. Although
both people and cat may move with the speed that will trigger motion, they have different size
of triggered pixels. For example, a human passing by the motion detection region will trigger
25% of pixels in that region while the cat would trigger only 2%. Since we want to have a real
alarm in case of human or vehicle passing by while ignoring birds, cats, butterflies, mice, etc,
we need a filter that can define how many percent of triggered pixels will be considered as a
real alarm. This parameter is called
trigger threshold
. The default value of trigger threshold is
10%. It means, only the objects that are bigger than 10% of the motion detection region size
and move faster than allowed by sensitivity level (70) will produce actual alarm.
How to choose the most optimal trigger threshold level? The rule of thumb,
keep the trigger
threshold as small as possible while not causing false alarms by the moving objects
that are not humans or vehicles.
You can have different sensitivity level and trigger threshold level for each motion detection
region.
In order to understand all of the above even better, please refer to the table below containing
four possible combinations of settings using sensitivity level and trigger threshold percentage.
