Thermography

What are the most important specifications of thermal imaging cameras and what do they mean?

Infrared Resolution

The IR resolution of a thermal imaging camera describes how many image points (pixels) the thermal sensor generates to display a thermal image - that is, how many individual pixels make up a camera image. The more pixels there are, the more detailed the image and the more precise measurements can be. Unlike digital photographic cameras, which often have millions of pixels (megapixels), the resolution of thermal imaging cameras is significantly lower because the sensor measures infrared radiation rather than visible light. However, the highest resolution is not always necessary for thermography: if you can get close enough to the object, a more affordable camera with lower resolution is often sufficient. On the other hand, if small objects must be captured from a greater distance or very fine details need to be detected, higher resolution is required.

Thermal Sensitivity/NETD

The NETD value (Noise Equivalent Temperature Difference) describes the smallest temperature difference that can be detected with the camera. The lower the NETD value, the better the thermal sensitivity of the infrared system and the clearer the camera image. NETD is measured in millikelvin (mK) and is typically specified at 30°C. Higher sensitivity is especially important for applications where temperature differences are small.

Focus

Like photographic cameras, thermal imaging cameras differ in how they achieve focus. Some models have a fixed focus and provide consistently sharp images without adjustment. Others require manual adjustment by the user. Still others use autofocus and automatically adjust sharpness based on image contrast. Typically, simpler devices are equipped with fixed focus, while higher-end models offer manual or automatic focusing. Which option is best depends on individual requirements and the specific application.

Field of View (FOV) and Lenses

The portion of a scene that a camera can capture - referred to as the field of view (FOV) - is largely determined by the lens used. It describes how much of a scene can be recorded at once. Similar to photographic cameras, thermal imaging cameras may be equipped with standard, wide-angle, or telephoto lenses depending on the model. High-quality thermal cameras often also allow lenses to be swapped, enabling flexible adaptation to different requirements.

Temperature Range

The temperature range of a camera describes the minimum and maximum values it can reliably measure. Within this range, the device is calibrated and provides accurate results. Often a total range is specified, although some models offer multiple switchable measurement ranges to precisely capture both low and very high temperatures. Depending on the application, smaller ranges may suffice, or wider ranges may be required for extreme temperatures (e.g., industrial settings, furnaces).

Spectral Range

The spectral range indicates the wavelength window in which a camera sensor can detect radiation. This is typically specified in micrometers (µm). Most standard thermal imaging cameras operate in the long-wave infrared range between approximately 8 and 14 µm, which is particularly suitable for many common applications such as inspecting electrical systems or use in fire protection.

Other General Specifications

For convenient use of a thermal imaging camera, several additional general features may also be important, for example:

• Video: Can the camera only capture images, or also record videos (and in what quality) - if required?
• Display: Touchscreen or basic display. Display resolution: if the display resolution is lower than the sensor resolution, image data must be interpolated/upscaled, which can lead to blurring.
• Internal storage and data interfaces for transferring data to a PC. Is analysis software available?
• On-device analysis: What image analysis functions does the camera itself provide? Increasingly includes AI tools.
• Built-in megapixel camera: Resolution and features such as image fusion/overlay of real and thermal images.
• Practical additional functions: Voice and text annotations, scanning of QR/barcodes, etc.