Evaluating LED Technology
LED technology has been a hot topic for several years with various attempts to balance the strengths and weaknesses of this evolving technology. On the positive side, LEDs are nearly indestructible and grow notably brighter each year. Yet, many manufacturers overdrive LEDs in order to get the brightest possible light. Unfortunately, overdriving may increase heat and system stress, reducing light efficiency and ultimately sacrificing battery run time (because energy is lost in the form of heat). Meanwhile, the front-emitting (as opposed to side-emitting) nature of an LED diode challenges the effort to efficiently focus a tight beam. This is because light emanating forward is hard to focus tightly, whereas light projected from the side of HID/Halogen bulbs can be more easily collected in a reflector and focused. Overdriving LEDs can reduce some of this problem but results in the previously mentioned weakness. Collimators are another technology used to focus LED output and act as a sort of magnifying lens that can collect and focus the output. Other creative designs support focused lighting but at the expense of protecting the LED array (diodes and control board), which reduces the value of the technology. HID and Halogen bulbs are relatively fragile and dropping the light head will usually result in damage. Therefore, a typical test tube-style light is not at a disadvantage as the enclosure is similar (if not a bit stronger) than the bulb itself. Meanwhile, an LED array is quite resilient and benefits from a more robust enclosure.
Given the current state of LED technology one must select a balance between battery run time, light output, light focus, heat accumulation, system stress, and LED protection. Any diver looking to balance these various issues should also develop a new vocabulary for talking about the way LED lighting can be compared. Please see the accompanying discussion entitled “Evaluating LED Output” for more information regarding this vocabulary. One should also consider the different ways in which LEDs are energized for light output. For example, some LED diodes are “unregulated” while others are “regulated.” An unregulated system draws power more or less directly from the battery source, whereas a regulated system uses electronics to control the current supplied to LEDs. This latter system uses the battery more efficiently and maintains a nearly constant intensity. In this way, the output remains consistent up to the point the battery voltage reaches a safety cutoff (a voltage protection circuit will intervene). This control board also allows creative power utilization. For example, by adjusting the light output to half, we can roughly double the battery’s run time. An unregulated system would burn brightly at the start but would usually decline fairly quickly. This system will usually produce light for a very long time (thus the multi-day burn promoted by some) but the light output becomes more or less useless relatively early in this scenario.
A light manufacturer’s efforts to create the “best” light involve balancing the previously mentioned variables. In other words, anyone can create a bright LED (using lots of power but creating heat and stress) and some can create a focused LED (more or less) but the way these factors are balanced, applied, and then protected by a given system (light and battery enclosure) are probably more relevant to an individual’s selection criteria. Given the current state of LED technology, Halcyon LED systems tend to utilize an intense light output (good total volume with a reasonably tight beam) with premium LEDs; these are capable of generating strong light output while consuming modest power and generating easily manageable heat. These diodes are driven by a regulated board, which optimizes light output while allowing user adjustable intensity; this adjustment enables extended run time or more intense lighting as the situation requires. Finally, this LED array is housed in a robust and durable housing that can easily withstand demanding travel and diving environments.
Evaluating LED Output
Lumens are a measure of the total number of packets (or quanta) of light produced by a light source (e.g., a globe or fluorescent tube). This is the “quantity” of light emitted by the light source. This measurement of total light is relevant, though probably not extremely useful for most diving applications.
Lux is a measurement that defines light intensity at a given distance. A lux measurement that is very close to the light source will be higher than a lux measurement recorded farther from the same light source because light diffuses as it gets farther from the source. Therefore, you can think of lumens as the amount of light available and lux as the lumens that are actually arriving at the intended target.
Approximate guideline values:
0.27 lux = full moon on a clear night
50 lux = family living room
320-500 lux = workplace lighting
1,000 lux = overcast day or typical TV studio lighting
10,000-25,000 lux = full daylight (not direct sun)
32,000-130,000 lux = direct sunlight
Measuring Diving Light
Halcyon prefers to describe diving lights using lux because this provides a gauge of intensity at a given distance, which is probably more relevant while diving or during signaling. It is important to note that when a lux rating is used, it must be associated with a distance. Lux values will vary at different distances. Halcyon manufacturing typically tests lux output at one, three, and five meters (approximately three, 10, and 15 feet) from the light source. These distances appear useful when evaluating intensity for general use and while signaling a dive buddy.