What Do The Colors Mean In Thermal Imaging? Are they the same for all models?

May 6, 2021

You probably have seen a thermal image of objects or living beings in movies or on the Internet. Visually, the picture seems very simple and understandable, but in practice, everything is much more complicated. Thermal images can have different color palettes, which means they can display the temperature of objects in different ways. If you decide to buy a thermal optic, you should know the types of palettes and know what is the meaning of the colors they display? In this article, we will talk about the most important points that will help you easily “read” every thermal image.

What is the meaning of the Colors?
The thermal Imager does not need light or extra illumination of the surrounding space to work. Such a device reacts to the heat that is emitted by almost all objects around us. This equipment works in a rather primitive way – its sensors capture the information about the sources of heat and their temperature and record it. To process this data, special software is needed. Exactly software is responsible for the accuracy of converting a thermal image into a digital one.
The simpler the software, the simpler the gotten image will be. That is, the display may not show objects with a low temperature, but only warm and hot objects. Expensive thermal imagers would show a more detailed and clear image, vice versa cheap devices will make the image simpler. To improve cheap equipment, manufacturers add an extra camera on inexpensive models. Its task – to record a visual picture of the surrounding space. With the help of software, the two obtained images are superimposed on each other thanks to what the final image is displayed more realistically.

Types of color palette
In cheaper models, the image is usually displayed in black and white. It is rather difficult to understand what is happening on the screen, you need to have experience and practice before use. Such type of equipment is inexpensive and belongs to the earlier generation of thermal imagers.
In modern thermal imagers, the image is displayed in different colors. Depending on the palette, they can display from 3 to 16 colors. The more colors in your palette, the more detailed and understandable the image will be. In the standard color palette, red, yellow, and orange are responsible for displaying warmer and hotter zones, while purple, blue, and dark blue are responsible for displaying colder zones. Classic black and white versions are also available in the latest models and their palettes can be adjusted to show black or white as hot objects as well as colder zones, depending on the user's preferences.

Rainbow, Lava, Iron, Arctic. These are the colored palettes. Each of them uses a different number of colors and displays the temperature of an object in a different way. But the displaying principles remain standard – cold in a dark color, warm in a bright color.

You need some practice to work with colored palettes. For example, let’s look at an animal/bird with thick fur or feathers (bear, sheep, ostrich). Thick fur does not allow heat to pass through, so a thermal imager will show such areas in dark (cold) colors. In this case, this does not mean at all that the animal has a low body temperature. But the mouth, eyes, and nose of the animal will be displayed in bright colors. If looking at an animal with short fur (lion, horse), all parts of the body will be “visible”, and will be displayed in light bright colors. For better color palette understanding, it is worth knowing three important points in thermal imagers adjustments – color map, temperature base, and temperature range. Let's examine each criterion separately.

Color map
The temperature map is the number of colors in which your thermal image will be displayed. The fewer colors that include the map, the simpler your image will be. The standard color map includes 16 colors, while the simplest one has only 3 (red, blue, and green). The grayscale map includes several shades of gray. If you are not a professional hunter or military, you should choose a standard temperature map, since grayscale or “three-shade” maps are quite difficult if you need to quickly determine the target and aim.

Temperature base
These are the top and bottom temperatures that the thermal imager will capture. It is very important to correctly adjust these parameters, or it depends on how accurately the device will transmit the thermal image of the environment.
The standard settings are 8 degrees in the range from 27 to 35 degrees Celsius. These temperature frames are usually enough for identifying living beings and warm objects (a running car engine, hot water pipes, etc.). If you change the base to 1-2 degrees higher or lower, you can lose a lot of important details. Therefore, before setting the temperature base, it is better to make several tests to know how the screen will display living beings and objects.

Temperature range
Each color at the temperature map represents a certain temperature range. For example, at 16 colors temperature map with standard settings, each color corresponds to a temperature of about 0.5 degrees. This is quite enough for a clear display of the thermal image. If you narrow the temperature base to 4 degrees, each color will now represent not 0.5 degrees, but 0.25. By narrowing the temperature range, you can make the picture clearer, but at the same time, you will lose image elements that do not fall into it. By widening the temperature range, you can cover more heat sources, but they will be displaying more blurry and not as detailed. Summary
Thermal imagers are several times more expensive than usual night vision devices, but this is due to their fantastic functionality. They can show you all hidden objects, which emit heat. But if you have no experience with temperature maps, you should start with the one that will give you a very clear picture of your surroundings. Pay only for quality and functionality – buy from a trusted seller!