IR Indoor vs OutdoorsBy: John Honovich, Published on Oct 29, 2012
IR 'works' much better indoors than outdoors, even if the light levels are equally as low and the distance is equally as far. This might sound weird at first but it is an important and fundamental issue that is critical in planning and assessing the range of integrated IR cameras.
The key difference is that indoors, IR light can reflect off of walls that are typically white or light color. This reflection helps increase the illumination effectiveness of the IR. By contrast, outdoors, IR light sent from the camera shines into the black distance.
We verified this in our IR illuminator performance test. Funny enough, we asked one manufacturer how they rated their IR illuminator for 100 feet. He described how the test was done inside of a warehouse with the IR illuminator shining off the back wall of the building.
In our tests, we found this to make a massive difference. We suspect many, or most, manufacturers also assume such indoor walled off tests.
In the rare case, you have a big dark indoor area to monitor, IR may work up to the manufacturer's specification. Otherwise, outdoors, be careful and assume only half the max distance.