I recently wrote this for use at work:
LEDs are not “bulbs”. They are diodes that emit light. LED means “Light Emitting Diode”.
Unlike a traditional light bulb that emits light in all directions, LEDs are flat modules that emit all their light to the front from a very small surface. This makes focusing LEDs “on-the-fly” difficult to achieve and impractical. This is also why LED lights often have a blinding effect.
An LED’s brightness will dim with use. The life expectancy of an LED is determined when the LED reaches 70% of its original brightness. The LED life expectancy can be increased by lowering its brightness.
An LED’s enemies are heat and excessive current. Both will greatly reduce its lifespan.
Only use the level of brightness you need for the job. This will reduce eyestrain caused by reflected light, and it will extend both the battery life and the LED’s lifespan.
Unlike incandescent light bulbs, LED lights can switch on to full brightness very quickly. This makes them ideal for strobing.
The circuitry that drives the LED is important in its performance and durability. For example, circuitry that uses plastic capacitors will not perform as well as one that uses higher quality metal capacitors. While the LED module itself may have an impressive lifespan, that won't mean much if the flashlight fails due to poor quality materials or workmanship.
How the flashlight manufacturer focuses the LED light source is very important. This will determine both the light’s distance and its spill factor. Tightly focused lights (often achieved through magnification to get distance) create a narrow beam with little to no light spill. This creates a spotlight effect, which is not desirable in most situations. Ideally no magnification is used, and instead the refractor is designed in such a manner to achieve both distance and spill.
Refractors can be polished or “orange peel”. Polished refractors generally achieve better distance, but the light can have unpleasant sharp lines. Orange peel refractors produce a more even and pleasant light, but may not achieve the same distance as a polished refractor.
White LEDs actually emit blue light. They are covered with a yellow film to give the light a white appearance.
LED’s do not heat up like a traditional light bulb. This is why LED traffic lights don’t melt the snow off like they used to.
Most LED tactical-style flashlights operate on either disposable CR123A lithium batteries, or rechargeable 18650 lithium-ion (Li-ion) batteries. Many are capable of using either one or the other. A single 18650 Li-ion battery will replace 2 each CR123A lithium batteries.
Fun fact: Each Tesla automobile utilizes over 6,800 Panasonic 18650 Li-ion batteries in its battery pack.
