Q: How far away can I see a hot spot? How far can I see with a FLIR ONE?
A: You can see a hot spot or detect something hot a lot farther away than you can measure a hot spot. And how far you can see or detect a hot spot is a function of how hot the object is relative to its surroundings. The bigger the temperature difference, the easier it is to see. Most of the cameras can detect temperature differences of .1°C or better.
Thermal cameras, like visible cameras can see as far as your eye can see in most cases. Whether you will “see something” at a given distance depends on the size of the size of the object and the contrast. The difference is that we are talking about thermal contrast, not color contrast as with visible cameras. The rules are slightly different in the thermal world in that we are looking for objects that are hotter or cooler than their surroundings. Typically, the FLIR One will detect a human from about a 100’, but in this image, we can clearly see the sun (don’t try this at home) at about 93 million miles away.
Q: How far away can I see a person?
A: The FLIR One will detect a person at about 30m (or 100’) under good conditions, meaning you will see a hot spot. With the FLIR One PRO under the same conditions you will detect a person at about 40m (or 130’).
How far away you will be able to detect a person using a thermal imager is a function of the lens field of view (FOV), the number of pixels and the ambient temperature (or the difference between a person and the surrounding temperature). These are optimal conditions with a cool background and a warm human, so results will vary with environmental condition.