1. Diffuser
a. A method of softening the beam of a dive light, usually to reduce beam artifacts, via a translucent film or material placed over the lens
b. A translucent attachment to make a dive light serve as a camping lantern.
2. AR coating
A lens designed to offer better throw. “Aspheric” because it does not have the classic lens shape, the shape of the lens is not spherical. This dramatically increases costs. Most affordable ones are injection moulded optical plastic. “Aspheric” means “not a part of a sphere”
3. Beamshot
It’s a picture of the beam of a dive light, usually on a white wall, or outside on plants.
4. VF
Forward Voltage (a property of an LED). The voltage drop across a LED at a given current. If two LEDs are identical except one has a lower Vf, the one with the lower Vf will draw a higher current from a battery and will also be brighter.