Visible light enables you to see all kinds of things in your surroundings. This light is the only part of the electromagnetic spectrum that human beings can see. However, visible light only represents a small area of the entire electromagnetic spectrum. Infrared radiation typically consumes a larger share of this spectrum. All objects absorb, reflect and transmit energy at different levels. In addition, different materials will radiate heat or cold energy at different rates. Infrared cameras and equipment can detect this transmission of heat and display the result as images.
 
If you go shopping for thermal cameras, you will come across a diverse selection of products. You could invest in high-end models that offer a comprehensive range of features. Or, you could consider purchasing the basic models that offer limited functionality. These basic models will usually read the temperature of the fixed centre crosshairs on the display. In contrast, higher-end models offer multiple features that enable the user to select multiple crosshairs and draw comparisons between them. This comparison feature would enable the user to view the high, low and the average temperatures on display.
 
Most infrared imaging thermal cameras will come with user-selectable multiple colour palettes. These will enable the user to select between black and white displays or iron or rainbow displays. Home inspectors often use the iron palettes on their infrared cameras. The black and white palette enables the user to identify details on an image that the camera produces. Similarly, the rainbow palette is ideal for displaying the differences in temperature levels of various objects. Not surprisingly, cameras with this palette feature the best thermal sensitivity levels.
 
Other features that thermal cameras might have include:
 

• Colour Alarms: These enable the user to specify a temperature range. The camera will only display a colour thermal image of all objects having heat signature ranges either above or below the selected temperature range.
• Picture-in-Picture: This will display a colour thermal image within a standard digital image. The first image will usually be a quarter of the size of the display area.
• Fusion or Blending Capability: This feature enables the user to blend either maximum, minimum or average temperature of the thermal image with a standard digital image. In many cases, only high-end models have this feature.

Thermal energy can come from a combination of sources. Some objects have the ability to create their own heat. For instance, people and animals create heat via biological processes. Similarly, machines and vehicles rely on mechanical processes for creating heat. In addition, other objects tend to absorb heat from the sun during the day. Thereafter, they radiate this heat during the night. These objects would typically comprise land, vegetation, rocks etc. Different materials can absorb and radiate thermal energy at different rates. So, an area that you might consider as having a uniform temperature could well have a range of subtly different temperatures. To cite an example, a log exposed to direct sunlight will have a different heat signature when compared to a log that you have immersed in water. An infrared camera can detect this difference in heat signature. Therefore, it can produce an accurate visual representation of the heat signatures of the two logs.
 
Many people will feel that infrared cameras are only useful for security purposes. As such, they can help security personnel guard properties more effectively. However, these cameras offer immense value in a myriad of applications. Some of these could include:
 

• Energy Audits: If your home’s insulation is ineffective, you could find yourself paying high electricity bills. You might not be able to figure out where the leaks are with your naked eyes. But, infrared cameras can capture the exact spots from where heat escapes from your home.
• Firefighting: When firefighters enter blazing buildings, they face a significant threat to their safety and well-being. After all, some fires could be burning out of sight. Similarly, buildings on fire could have thick smoke that makes it hard to see properly. Infrared cameras can spot people trapped in the fire based on their heat signatures. Similarly, they can identify areas where a fire is burning out of sight e.g. under a floor etc. as well.
• Military Applications: Thermal imaging enables officers to discern objects through various forms of camouflage. The naked eye might not be able to discern an ambusher concealed in dry leaves and twigs. But, infrared cameras will be able to reveal an object with a higher heat signature concealed beneath the leaves.
• Miscellaneous: Law enforcement agencies use infrared cameras for managing surveillance-related activities. They use them for locating and apprehending suspects and investigating crime scenes. These cameras are good for launching search and rescue operations too. Maintenance technicians working on power lines use infrared cameras for spotting overheating joints. This enables them to eliminate potential failures. 

It is worth highlighting that heat and light are both parts of the electromagnetic spectrum. But, thermal infrared cameras can detect heat, while regular cameras cannot. Similarly, regular cameras can detect light, while infrared cameras cannot. But, certain camera manufacturers have emerged with regular cameras that can produce images of objects in even dim or poor visibility conditions. These night vision devices have become quite popular all over the country. They often produce greenish images, which many people might have come across while watching television or movies.
 
Night vision devices suffer from the same constraints as regular cameras do. In case the amount of visible light is not sufficient, the image produced will not be very clear. These devices usually take in small amounts of visible light. Then, they magnify this light significantly for producing images. This makes it evident that these cameras can be useful at night, when regular cameras might not be able to function all that well.
 
However, even night vision devices need some amount of visible light to magnify. Without it, they will hardly be able to produce high-quality images. For instance, in twilight, the human eye might not be able to see very clearly. This is because there is not enough visible light that makes it easier to see objects. However, the amount of visible light in twilight will be far too much for night vision cameras to operate effectively. As such, they will not be able to produce good images even in these conditions.
 
In contrast, infrared cameras rely on heat for producing images, and not light. Every object typically gives off thermal energy i.e. heat. You might feel that ice might not emit any heat, but this is not true. People refer to this emitted heat energy as the object’s heat signature. Infrared cameras can easily discern the heat that an object emits and depict this in an image. These cameras can even highlight the variations in the amount of heat emitted by two objects next to each other. 

Regular and security cameras typically work best in natural light. Some devices offer enhanced levels of functionality. Their features enable these devices to generate better quality images even in low light conditions. Regular cameras usually find it easy to generate colour images in natural light. To generate clear images, these cameras typically filter out infrared light. Infrared light can distort the colours of the images in comparison to the image as seen by the human eye. To filter out infrared light, these cameras feature infrared-cut filters. As natural light diminishes below a certain level, these cameras usually switch over to and start functioning in the night mode. In this mode, these cameras will remove the infrared-cut filter. As such, the camera will use near-infrared light for delivering high-quality, black and white images. Near-infrared light typically spans from 700 nanometres to 1,000 nanometres. The human eye cannot discern this frequency of light. But, most camera sensors can detect it and utilise it for producing images.
 
The principle behind which regular cameras function is easy. Our eyes can see objects in reflected light. So, visible light energy hits an object and bounces off it. This enables us to discern the object clearly. Daylight cameras and night vision devices operate on the same principle. The detectors in these cameras receive the light that bounces off an object and turns it into an image. But, these detectors will need to receive sufficient amount of light. Without it, they will not be able to produce an image. This is why many cameras cannot produce high-quality images when used in starlight, moonlight or artificial lights.
 
However, infrared cameras have the ability to overcome this dependency on light. People refer to these devices as cameras. But, in reality, you could just as well call them sensors. Regular cameras produce images by using visible light. In contrast, infrared cameras do not rely on visible light. Instead, they use heat for producing images. In addition, infrared cameras can even detect variations in the quantum of heat that an object emits. This enables these devices to produce images as shades of grey in black and white images.