Just a clarification for anyone reading this down the road. Any camera system that mentions NDVI is using near-infrared (NIR) light, the band(s) just beyond visible red light. Near-infrared is only useful at night if you also provide a light source; since the light source would also be NIR, it is invisible to the naked eye. This is one approach used by inexpensive cameras that "see" in the dark. Most digital camera sensors (CCDs) already detect NIR light, but have a filter added to the sensor to purposely block it. You can remove this filter on many cameras, turning it into an NIR-capable camera (there are companies that will do this for you); however, you'll probably want to add an additional filter to restrict one or more of the visible light bands in its place, as most cameras are designed to record 3 distinct bands (red/green/blue). Lots of info about this on the web.
The FLIR cameras are thermal infrared sensors - they measure heat. Thermal infrared is much further along the electromagnetic energy spectrum than NIR light, and is much, much weaker and more difficult to detect. Hence, the slow exposures and, in the past, big lenses on thermal infrared cameras. Since thermal infrared cameras are not measuring light, they will work in total darkness, as long as the temperature of objects is within the range of the sensor. The better FLIR sensors will "see" temperatures down to -40 deg. C!!
Hope that helps to clear up any confusion.
The FLIR cameras are thermal infrared sensors - they measure heat. Thermal infrared is much further along the electromagnetic energy spectrum than NIR light, and is much, much weaker and more difficult to detect. Hence, the slow exposures and, in the past, big lenses on thermal infrared cameras. Since thermal infrared cameras are not measuring light, they will work in total darkness, as long as the temperature of objects is within the range of the sensor. The better FLIR sensors will "see" temperatures down to -40 deg. C!!
Hope that helps to clear up any confusion.
