Closed Circuit Television.
I think most people would agree that customers expectations for everything in life are far higher than they have ever been and when an end-user say they want their cameras to work in low light, very often they actually mean to say no light!!!
If most installers were brutally honest they would agree it’s hard to please everyone all of the time.
Picking the right camera
However picking the correct camera for the correct location and to do the correct task can greatly help to get customer satisfaction first time round.
It is important to understand every CCTV camera needs some light to operate. However some cameras can use “light“ that’s invisible to the human eye. We call this infra-red (IR) light.
Because CCTV cameras can use this IR light to see what appears to be total darkness to us humans, many CCTV camera manufacturers have produced cameras with built in IR illuminators. It is important to know the limitations of this technology as in the real world, these cameras do indeed have limitations.
CAMERAS WITH BUILT IN IR LEDS
The IR LEDS built into the cameras can give illumination in areas with no other light source.
However its really important to understand that the actual output power of the built in IR LEDS is very low, typically 3-10 watts. If you think of how bright a 10 watt bulb is, you will quickly come to the conclusion “not very”. this is why cameras with built in IR LEDS will not actually illuminate a very big area.
The IR illuminators built into these cameras are best thought as “ invisible torch lights” just like a medium powered hand held torch. So what you could see with a torch, you would more or less get with these IR cameras.
Like a torch, the IR light is very directional more of a spot light than a floodlight. Of course some IR cameras are more powerful than others but few, if any, can offer any genuine useable “floodlighting“ of any kind.
Effective illumination from cameras with built in IR illuminators are also rapidly decreases with distance.
In fact if you double the distance you get a ¼ of the illumination, this is called the inverse square rule.
Because the built in IR illumination is very much a torch light, users of such cameras will often describe peoples faces being “bleached out “just like shining a torch at someone’s face close up !
This can be a real problem with cameras with built in IR lights.
If this reflection is a problem and you get “ bleached out “ faces then the camera is generally too close to the subject its looking at or the IR illuminator is too powerful for the location its used in such as an entrance porch.
The third problem with cameras with built in IR illuminators is IR reflection from insects and spiders, this can be the curse of many installers and users of CCTV equipment!
Because insects such as spiders are drawn to the gentle heat of the CCTV cameras they will often set up home in or on the cameras! The real big problem is when the IR light emitted from the camera hit’s the insect or spiders web and its reflected straight back into the cameras lens as bright illumination. You don’t get this reflection with other cameras as the light source is the other side of the spiders web and therefore causes no reflection.
So where can you use IR cameras?
Good question.
The best answer is wisely
If used indoors the IR light will often bounce around the room and the “spread“ of the IR light produces better images with less glare. This is because as the IR light bounces around the room it “illuminates“ the subject from many different angles and this produces “ shadowing “ it is the shadowing that produces detail in any picture that gives depth and detail.
For example you can only see someone’s wrinkles because of the shadows they create.
If the camera is low down and close to a person, for example in a porch, you need a low powered IR one so a visitors face doesn’t get too much reflection. However you will not see very far as the illumination at a greater distance is too weak.
If the camera is higher up and looking down on an area, you need a much , much higher powered built in IR illuminator to light up the area and faces will not be quite as reflective due to the angle of the IR light being more incidental to the face.
