Why are we interested IR and UV? Perhaps it is just a slightly-away from normal means to monitor our surroundings. Perhaps it is simply a matter of easy access to the technology. Again, there is no scientific basis behind IR and UV having any relationship to the unusual events we seek to explain. Thermal imaging is within the realm of IR but will not be discussed here. The primary intent of this discussion is to illustrate the limitations of the technology we use. Research your equipment to understand exactly what it is and isn’t providing for you.
A “full spectrum” camera is not capturing a full spectrum image. With respect to the visual bandwidth, standard cameras are already “full spectrum”. The specifications of the sensor in the camera will indicate sensitivity to frequencies beyond that of human vision. Filters are added to the light path in the camera to block infrared and ultraviolet along with software interpretation of the data from the sensor to result in an image our eyes and brains recognize. What is marketed as “full spectrum” simply has the IR and UV filters removed. This allows a wider bandwidth of frequencies to reach the camera sensor. All we are actually achieving with a “full spectrum” camera is a level of enhancement to the tiny portions of the IR and UV bandwidths our eyes already perceive.
Potentially increasing the discrepancy, we tend to use LED illuminators. LEDs emit a very specific frequency. If whatever we are trying to enhance is at a different frequency, the LED illuminator may be washing out the image preventing capture of the desired image. Also, without understanding the specifications of the camera sensor, the illuminator we choose may not emit a frequency the camera can sense properly regardless of the intensity of the LEDs. Be sure to understand the light wavelength/frequency the given camera and illuminator are designed for. There are alternate non-LED illuminators but these come with heat/fire risks from IR lamps and potential eye and skin damage from UV lamps.
More effective IR and UV image systems are available but may come at significant cost. We see IR imaging every day associated with “FLIR night vision” systems and satellite/telescope imagery. UV imaging is not as prevalent in the media but we may hear mention of it related to forensics and utility troubleshooting as well as satellite /telescope imagery.
A few typical sensitivities/specifications to consider:
For perspective; 1 Hz is once per second, 1 THz is 1,000,000,000,000 times per second
Infrared bandwidth: 300 GHz to 430 THz
Ultraviolet bandwidth: 790 THz to 30,000 THz
Typical human vision sensitivity: 400 THz (red) to 790 THz (violet)
Typical unfiltered camera sensor sensitivity: 303 THz to 999 THz
-covers about 29.56% of the IR bandwidth
-covers about 0.5% of the UV bandwidth
Typical Infrared LED emission range: 316 THz to 353 THz
-about 8.6% of the IR bandwidth (best case using a wide variety of IR LEDs)
-a typical LED illuminator operates with numerous LEDs of a single type. Since each LED type emits a specific frequency, a typical IR illuminator is providing illumination equivalent to 0.0002% of the IR bandwidth or about 2% of the effective IR range of an unfiltered camera. These number are even less effective for the UV bandwidth.
Typical Ultraviolet LED emission range: 749 THz to 821 THz
-about 0.2% of the UV bandwidth (best case using a wide variety of UV LEDs)
Again, an excellent graphic showing the EM Spectrum (thanks to Sparc Para Analytics):
Professional camera conversion: