What does instantaneous field of view (IFOV) tell you in infrared thermography?

• A. The angle of view of the camera
• B. How large an area on the ground a single pixel can theoretically see
• C. The spectral range of the sensor
• D. The maximum resolution of the image

Answer: (B)

Instantaneous field of view is about how much of the scene each pixel can capture. It’s the angular size of a single pixel, which you can translate into a ground footprint if you know how far away the target is. The footprint on the ground (one pixel’s area) is roughly the distance to the target times the tangent of the IFOV. For small angles, you can use a handy approximation: footprint ≈ distance × IFOV (in radians). This matters because it directly sets the spatial detail you can measure in a thermography image—the smaller the footprint per pixel, the higher the spatial resolution. It’s not about the camera’s overall viewing angle, the sensor’s spectral range, or the image’s total pixel count.