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The Chairman

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OK,

I have grown up always referring to light intensity in terms of "Watts". That fell through when I started looking at fluorescent and Hi Intensity lights, but quite often they were compared to a particular wattage of an incandescent light.

NOW, I have to assimilate LED (measured in Watts) and HIDs (measured in Watts). Is there an easy way to compare them all. Sure, we have lumens and "color", but what do they really mean to ME the diver.

Help us out Carl!
 
OK,

I have grown up always referring to light intensity in terms of "Watts". That fell through when I started looking at fluorescent and Hi Intensity lights, but quite often they were compared to a particular wattage of an incandescent light.

NOW, I have to assimilate LED (measured in Watts) and HIDs (measured in Watts). Is there an easy way to compare them all. Sure, we have lumens and "color", but what do they really mean to ME the diver.

Help us out Carl!


Well, incandescents (filament lamps) have been around for a really long time, so it is natural to use them as a reference when trying to quantify brightness. The problem with that is that an incandescent wastes a lot of the energy in the form of heat or as light that is not visible to us. Fluorescent, HID and LED lights put much more of their used energy into the visible spectrum (stuff we can see) and produces a white light (like sunlight) that allows us to see differences in color and contrast more easily. This is why we say that a 21 watt HID is comparable to a 100 watt incandscent, because of the area and intensity of illumination seems almost equal.
Lumens is a real measure of useable light, but not all measurements are created equal, that is, if you measure the lumens output at the source it will not tell you how much useable light you will have at a target a given distance away. The light source needs an optic to put the light into a form that we can use. This is where LEDs and HIDs part company. A HID (High Intensity Discharge) lamp is small glass tube that contains a mixture of materials that, when properly electrically excited, create an electric arc or plasma in a very small area in the tube. This small spot of intense light is perfect for use with a simple reflector to create a focusable system that can create a tight beam that can illuminate a target at great distance. The new high powered LEDs are very bright (high lumen output) and very efficient (high number of lumens per watt of energy used), but the amount of light output is pretty much dependent on the active area of the LED, which is essentially a flat surface that is giving off light. This larger flat illuminator requires a more complex optic to create the same tight light pattern as an HID and adjustable focusing is even more involved. While the technology of LEDs and their optics are changing on a daily basis, the typical tightest LED optic will get a beam spread of about 10 degrees, while an HID can get about a 3 degree beam spread. What does this mean to the diver? If you are diving in water with a lot of particles you would want as tight beam as possible so that it illuminates the smallest area possible in front of you and produces you less backscatter while illuminating a distant target. Now aren't you sorry that you asked?
 
Now, how does that relate to the term "candlepower"? My husband asked how many candlepower my light had because "X" watt HID and LED meant nothing to him. We have a 10,000 candlepower spotlight and he wanted me to relate it to that.
Ber :lilbunny:
 
https://www.shearwater.com/products/swift/

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