Published on September 21, 2018 by Matt Garnham in Helpful Article Blog Posts
Identification vs Recognition vs Detection
Hopefully this blog post will dispel some of the myths that revolve around the various different distances that get talked about in the security camera industry.
I’m sorry – this really is not a very interesting subject. It is however important for your security camera system.
This is one of the key points of security camera systems that most people neglect when specifying their security camera system. It is also the one area that the marketing people of most of our competitors convince you a camera with a 3.6mm lens can identify someone at a great distance (it can’t – approx 20 feet).
Let’s first discuss what each of these terms actually mean.
Identification Distance of a Security Camera
Identification distance is the maximum distance a person can be from the security camera to capture an image that will allow the identification of a totally unknown person. For example, if an unknown person stole your car, how close would they have to be to the camera to allow the police to identify the perpetrator.
This is the most important distance when it comes to security camera systems. It is the only one that we are interested in here at Orange Security. When you see a distance specified on our website it is always the identification distance (unless specifically stated otherwise).
Recognition Distance of a Security Camera
Recognition distance is the maximum distance a person can be from the security camera to capture an image that will allow the recognition of a known person. Let’s take the same example above of your car being stolen. If the thief happened to be your brother – a person you knew very well – you would be able to recognize him at a much further distance than you could identify him.
Detection Distance of a Security Camera
Detection distance is the maximum distance a person can be seen on the security camera to be within an area. It’s a broadly useless number and we pretty much never use it here on our website.
These Different Distances
There is no clearly defined cut off between any of these three distances. It’s not like at 49 feet you can identify and at 50 feet you can only recognize a person. There are also many other factors that can affect each of the above distances that just can not be accounted for (such as day/night, direction of the sun, other lighting in the area, how the person is moving etc). For this reason, any figures that we state on this website are generally on the pessimistic side. We do this so as not to disappoint.
Where does IR Range come into it?
Another distance that is often bandied around when it comes to trying to get you to part with your money is the IR range.
Put simply, this distance is the distance from the security camera that the infra red illumination can be detected. This number is usually greater than all the other distances put together. Because of this, some suppliers [no, I’m not going to name names] translate IR range into a meaningless ‘distance’ figure. The vagueness allows them to mislead customers into buying the wrong product. This then gives the whole of our industry a bad name.
Every security camera is specified with an IR range that extends beyond the ability of the lens it is fitted with.
This is a totally pointless figure and one to be avoided. If a supplier is using this number to sell cameras you will be best served by going elsewhere.
What Changes these Distances?
The biggest factor in causing these distances to increase or decrease for a security camera is the lens that is fitted to that camera. If the camera has a varifocal zoom lens then you can actually change this distance when you install. For example, a security camera with a 2.8-12mm zoom lens can be adjusted to identify anywhere from as little as 10 feet to as much as 50 feet. This depends on whether you set the camera at 2.8mm, 12mm or anywhere in between.
The other factor that determines what each of these distances are is the resolution of the security camera. Of course the resolution of the DVR recorder matters too.
Warning: Science Stuff Approaching!
For any given lens size (assuming the sensor size remains constant), the identification will increase logarithmically. If you double the resolution, the distance increased by approx 1.4 times (square root of 2). We do have a Full HD 1080p Resolution Advice Section on our website for more information. I may do a dedicated article on this topic in the future if people request it?
How do I know if the Distances Specified are Recognition?
Unfortunately this is a pretty common concern for customers buying their first security camera system. Without getting too technical, the table below should give you guidelines of what to expect for a full HD 1080p security camera system such as those we sell here at Orange Security:
|Lens Focal Length||Identification Distance|
The above numbers are cautiously pessimistic. What I mean by this is that if you have your security camera set to 12mm (that is the most zoomed in our popular bullet camera with 2.8-12mm lens for example can be set) you may well be able to identify people beyond the 50ft specified in the table above. However don’t rely on it!
Don’t let the appliance of science baffle you – if you are unsure about any products we sell…or for that matter products anyone else sells, reach out and my team will help you out.
about the author: Matt Garnham
Security Camera expert for many years. He is the founder and owner of Orange Security. Started life in the security industry in the UK. Relocated to Southern Florida and Orange Security was formed.