What is F-Stop and Why is the F-Number of the Lens So Important for Thermal Infrared Cameras?
An f‑number (ƒ/#) or f‑stop refers to the ratio of a lens’s focal length to its aperture’s diameter (lens opening vs focal length) and indicates the amount of IR energy (heat) coming through the lens to the infrared sensor. The lower the f-number the larger the aperture diameter, meaning more thermal IR energy is reaching the infrared sensor.
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Thermal Imaging Technology
![](https://fdn.gsmarena.com/imgroot/static/glossary/camera/gsmarena_010.jpg)
Camera - definition - GSMArena.com
![](https://www.optris.com/wp-content/uploads/2022/08/ir-camera-optris-pi-1m.jpg)
PI 1M: IR cameras for the metal industry - Optris
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What is F-Stop, How it Works and How to Use it in Photography
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FLIR E6 Thermal Imaging Infrared Camera, Thermal Imagers
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Why is Aperture Measured in F-Stops?
![](https://infraredcameras.com/hubfs/IR-Flash-Pro-Medical-screenshot-green-light.webp)
How Do Infrared Cameras Work?
![](https://fdn.gsmarena.com/imgroot/static/glossary/camera/gsmarena_052.jpg)
Camera - definition - GSMArena.com
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f-number - Wikipedia
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Understanding Distance:Size Ratio