Useful Information for LED Dive Lights
How is the luminosity of an LED dive light calculated or indicated?
The luminosity of an LED is given in lumens. Lumens is the unit of luminous flux. In photometry, this measures the radiated power in the wavelength range of visible light, which is measured in luminous intensity (cd) times solid angle (sr). Since manufacturers calculate the solid angle as 360 degrees, the lumens value is the total light intensity that the LED produces.
For a good dive light, it's crucial that the light is focused. Good reflectors for LED lights are hard to find. As a result, the luminance (measured in LUX) varies greatly between manufacturers, even when using the same LEDs in the lamp head.
Since the specifications are not standardized, different manufacturers provide different values.
Typical lumens per watt indications
Total Lumens / Luminosity
However, since the luminosity strongly depends on the power source, it's recommended to specify it per watt.
An LED operates at 3 volts and 550mA and has a luminous flux of 139 LM/Watt. This results in a light output of:
3 V x 0.5 A = 1.5 Watts
1.5 Watts x 139 LM/Watt = 208.5 LM
This example shows that stating the wattage for an LED doesn't provide a clear indication of its luminosity, since different LED manufacturers and types have different luminous efficiencies (LM/Watt).
Typical LEDs labeled as super bright produce between 11 and 70 LM/Watt; very high-intensity LEDs can produce up to 150 LM/Watt.
Comparison of Luminance of Various Light Sources
|Incandescent bulb - 100 Watt
|Fluorescent tube - 30 Watt
|Video projectors / Beamers
||approx. 800-2000 Lumens
|White 3W Power-LED (As of 2010)
||approx. 140-1100 Lumens
|White 1W Power-LED (As of 2010)
||approx. 60-110 Lumens
Batteries or Accumulators as a Power Source for Dive Lights
Generally, the use of batteries is discouraged since they don't ensure the required current draw, causing the voltage to collapse. This is due to the high internal resistance of batteries that limit the current. Therefore, the LED dive light cannot reach its full power, especially since batteries have an almost linearly decreasing voltage. The voltage of 1.5 volts drops continuously as power is drawn.
In contrast, accumulators have a much lower internal resistance than batteries, allowing much higher currents without the 1.2-volt voltage collapsing. Only at the end of their capacity does the voltage drop suddenly. Dive lights with deep discharge protection will switch off the light depending on the battery type at 0.8 volts to 1 volt per cell to prevent destroying the battery pack.
However, a warning: don't use batteries in lamps designed for accumulators, since the voltage of an accumulator is only 1.2 volts, while that of a battery is 1.5 volts.
Rechargeable batteries have a nominal voltage of 1.2 volts, and primary batteries have a nominal voltage of 1.5 volts. This difference is sufficient to destroy the LED if there is no constant current source built into the dive light, as it operates beyond its specifications.
Beam Angle of Dive Lights
With the beam angle, there's a slight peculiarity. Some manufacturers specify the total angle from the right to the left side. Others only from the center to the edge (where the standard is from the center to the edge - for instance, a specification of center to edge 11 degrees results in a total angle from right to left of 22 degrees).
However, manufacturers' specifications for beam angles are not uniform. Unfortunately, the details are sometimes very opaque and vary from manufacturer to manufacturer for dive lights.
Dive Light Manufacturers
Manufacturers of underwater lights and dive lights have switched from halogen bulbs to LEDs. Some of the dive light manufacturers still use discharge lamps, which are characterized by intense white light with high luminosity. This light is very close to daylight. The use of LED bulbs ensures a long duration of light even with low battery capacities. The batteries can be recharged quickly between dives during the surface interval.