It seems many lights, and primarily HIDs, are rated as 10W, 21W, etc. I assume that is input. While I can see that a light's input needs are of interest, isn't the output what counts? Are HIDs so standardized that equal wattage equates to equal output?
Why Watts?
- Thread starter pedo
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Good question. I'm not a light expert but I would imagine that it originates from this fact of physics: If you hold efficiency constant the output power is directly proportional to input power. Power draw is simple to measure and unambiguous. But you have to be aware that comparing different technologies (Halogen vs HID vs LED) based on power draw is pretty useless.
http://en.wikipedia.org/wiki/Lumen_(unit)
http://en.wikipedia.org/wiki/Lumen_(unit)
Hatul
Contributor
I agree the watt rating is not a positive criterion. In fact you want a light with a low watt rating and lots of light. I guess it's easier to make a light that uses lots of power than one that gives a lot of light with little power.
Adam
Adam
It's all a conspiracy to obfuscate the truth and get you to buy their product.
lucca brassi
Contributor
Because this is fine and simple orentation point on battery pack configuration and simple give us operating time . For example 10W HID in head 4Ah battery pack (almost standard is voltage tension on automotive 12V) but on the fast and rounded numbers (with rounded numbers also get real time because efficiency of electric circuit (complete (wires, switch , driver ...) is not 100% .....it is arround 85%+/-)
So 10V x 4Ah = 40Wh / 10 W = 4 h
FWADIVER
Contributor
It helps give you an apples to apples comparison among similar technologies, all the 10W HID will be pretty similar in bulb in output, though making the comparison across technology (LED to HID for instance) introduces a bit of apples and oranges.
DazedAndConfuzed
Contributor
before leds, lumen output is more or less proportional, one set of rule for incandescent light and another set for HID (although HIDs frequently specified light output). Look at home bulbs, one buys them based on wattage, lumens is just a byproduct.
Then LEDs came and its efficiency constantly improves, thus it doesn't pay to advertise the wattage since new models doesn't go up in wattage, so if they were advertising that, nobody would buy new lights. Thus the promotion of the lumens output.
Then LEDs came and its efficiency constantly improves, thus it doesn't pay to advertise the wattage since new models doesn't go up in wattage, so if they were advertising that, nobody would buy new lights. Thus the promotion of the lumens output.
Pedo, you were correct in your guess. Incandescent technology was stable so 100 watts meant something to the user. We all have a mental picture of a 100 watt bulb in our homes. HID continued with that. Divers have a mental picture of a 10 W HID.
It doesn't directly tell us anything about output (lumens or lux) and it requires that we already have that mental picture.
LED's are efficient and becoming more so all the time so lights are advertised in lumens. Some companies who don't really know what they are talking about still try to advertise their LED lights in watts but in many cases it's not even the actual watts...it's the halogen or HID watts that they think their lights are equivalent to!
There is one company that exaggerates their output figures that posts frequently in this forum. They look at a HID light and then shine their light on a wall next to it and decide that their light is just as bright and then advertise that figure. Never taking into account that two lights can be just as bright as each other in the central hotspot and yet have vastly different lumens figures...one has a bright but narrow beam for example and the other one has a bright but wider beam. The latter light outputs many more lumens. Or a light seems roughly equivalent to a HID but doesn't have that very bright point in the center of the beam that a HID has...their lux numbers will be very different which determines how far the light will "throw".
As was pointed out, it gets silly because they are trying to tell us to buy a light with the highest wattage figure which is like telling us to buy the car with the worst mile per gallon figure
The only use for an accurate wattage figure in a dive light is so you can figure out run times. If you know the watt/hour capacity of the battery it's using and diving the light wattage figure into that you will have your run time.
It doesn't directly tell us anything about output (lumens or lux) and it requires that we already have that mental picture.
LED's are efficient and becoming more so all the time so lights are advertised in lumens. Some companies who don't really know what they are talking about still try to advertise their LED lights in watts but in many cases it's not even the actual watts...it's the halogen or HID watts that they think their lights are equivalent to!
There is one company that exaggerates their output figures that posts frequently in this forum. They look at a HID light and then shine their light on a wall next to it and decide that their light is just as bright and then advertise that figure. Never taking into account that two lights can be just as bright as each other in the central hotspot and yet have vastly different lumens figures...one has a bright but narrow beam for example and the other one has a bright but wider beam. The latter light outputs many more lumens. Or a light seems roughly equivalent to a HID but doesn't have that very bright point in the center of the beam that a HID has...their lux numbers will be very different which determines how far the light will "throw".
As was pointed out, it gets silly because they are trying to tell us to buy a light with the highest wattage figure which is like telling us to buy the car with the worst mile per gallon figure
The only use for an accurate wattage figure in a dive light is so you can figure out run times. If you know the watt/hour capacity of the battery it's using and diving the light wattage figure into that you will have your run time.
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