Thermal vs. night vision: which low-light camera suits you best?
Source: Prasanth Aby Thomas, Consultant Editor
Gone are the days when surveillance cameras were only useful under the right lighting conditions. Given the various difficult conditions in which cameras are being installed these days, manufacturers had to come up with various ways to make sure lack of light did not hamper operations.
At present, there are two major technologies being used to enable cameras to see, thermal and night vision. In this write-up, we take a closer look at the advantages and disadvantages of these two technologies.
The first thing to understand about thermal cameras is that although for marketing and sales purposes they are called “cameras” they are not so in the traditional definition of the word. These are, in fact, sensors that can detect heat emanating from objects
. In a web post, one of the largest thermal imaging solution providers, FLIR Systems
“FLIRs make pictures from heat, not visible light,” the company said. “Heat (also called infrared, or thermal, energy) and light are both parts of the electromagnetic spectrum, but a camera that can detect visible light won’t see thermal energy and vice versa. Thermal cameras detect more than just heat though; they detect tiny differences in heat – as small as 0.01°C – and display them as shades of grey or with different colors. This can be a tricky idea to get across, and many people just don’t understand the concept, so we’ll spend a little time explaining it.”
To put it more simply, everything on earth emits some form of heat and this thermal energy that is emitted is known as a heat signature. Different kinds of materials absorb and radiate heat at different rates. Thermal cameras capture the heat signature and show the subtle differences in heat radiation in different colors.
Night vision cameras
Night vision is popular in Hollywood movies that show military action. Cameras that use this technology capture whatever little light is available and amplify it. Naturally, if there is no light to amplify, night vision doesn’t work well. But some might argue that in most situations, there will be some amount of light available.
“NVG and other lowlight cameras are not very useful during twilight hours when there is too much light for them to work effectively, but not enough light for you to see with the naked eye, says FLIR. “Thermal cameras aren’t affected by visible light, so they can give you clear pictures even when you are looking into the setting sun.”
That said, night vision can give you a visual that is comparable to what a normal camera can give, unlike thermal cameras, which basically just gives out different colors according to the heat generated. There are also talks about Infrared Cameras, which also fall under daylight cameras, that work by emitting infrared waves that can reflect on objects and help the camera capture it. But again, the limitations of reflected light limit the camera’s ability.
What to choose
When finalizing on what to buy, a key concept that you will need to consider is the contrast. If the visual in front of the camera has high contrast, daylight cameras with night vision will work well. Thermal cameras don’t have this problem.
“Thermal imagers don’t have any of these shortcomings,” FLIR points out. “First, they have nothing to do with reflected light energy: they see heat. Everything you see in normal daily life has a heat signature. This is why you have a much better chance of seeing something at night with a thermal imager than you do with a visible light camera, even a night vision camera.”
However, if you wish to have visuals that look somewhat similar to what a daylight camera captures, giving night vision an option would be a good idea.