Understanding Security Camera Pixel Density and Its Importance
What Qualifies as a ‘Good’ Security Camera Pixel Density?
If you have read our previous post “The Starting Line For Securing Your Premises”, then you might recall that security technology serves to provide one or both of these benefits on your property:
1) Prevent theft, vandalism or other crimes from occurring in the first place;
2) Provide useable forensic data after the fact if an incident does occur.
For a video surveillance system to provide useable forensic data after an incident occurs, there needs to be sufficient “pixel density” to allow an observer of the footage to see enough detail to be useable. Pixel density is often referred to as “Pixels Per Foot”, or PPF, and is used to determine how good the quality of an image will be in certain lighting conditions at certain distances. This could be to detect a person, read a license plate or notice if an object is moving. However, for forensic purposes, it is generally used for a persons’ face.
Axis Communications, one of the foremost network camera manufacturers and the inventors of the IP camera have done several studies on required PPF for various operational requirements, and uses the DORI Standard (Detection, Observation, Recognition, Identification) for levels of clarity in surveillance images with average lighting conditions:
- Detection (8ppf): An observer will be able to tell that a human is in the scene, but beyond that there is little detail.
- Observation (19ppf): Some individual characteristics such as clothing type or hair colour become discernable.
- Recognition (38ppf): An observer can tell with a reasonable degree of certainly if the individual is someone that they know. A license plate may potentially be readable in favourable lighting conditions.
- Identification (>80ppf): An observer can positively identify someone that they do not know beyond a reasonable doubt. License plates are easily readable.
Of course, environmental conditions will play a large role in being able to identify individuals as well. It is not critical that every system must meticulously go through each camera view and ensure there is sufficient pixel density. However, when you are deploying surveillance technology with the intention of being able to obtain useable forensic data in the event of an incident, ensuring sufficient PPF to be able to recognize or identify individuals in the “hot spots” is important – anything less might mean ending up with images that look unrecognizable.
There are several ways to get to good pixel density, such as employing varifocal-lens cameras, using cameras with IR night vision in some cases, or simply adding a few cameras to your plans. And if the space you want to view is small enough, you might get great pixel density without having to do anything special at all.
In any case, your team at Cabco will work with you to ensure you are getting what you need for a system you can be proud to own. For more information, contact our team at 1-800-675-4025 or reach out to Evan at emacauley@cabco.ca