L.E.D. string lights

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Hi,
What's the brightness (let's say per foot) of the L.E.D. rope lights in incandescent-light-watt-equivalent?
Thanks,
Sam
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Sam Takoy wrote:

Watt is unit of power(energy) There is no such thing as ILWE.
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They use a similar rating on the CFLs. GE, for instance, call their 13 Watt bulbs Smart 60.
They really rate bulbs in lumens, but we've used watts for over 100 years so there are a lot of habits to change. I don't know of anyone that looks at the lumens on the package.
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Sorry, that doesn't make sense. Watts are units of electrical power consumption (actually, that should be watts/unit time). For light output, the unit is lumen. The reason that is a bit misleading is because the actual energy output is in a subjective manner affected by the spectral distribution. And that distribution also determines whether the light is harsh or pleasingly warm. I think the best way to describe light is as so many lumens at a spectral temperature of so many degrees (usually expressed in degrees Kelvin). We're just not used to that way of expressing (yet).
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Watts are indeed a unit of electrical power, but watts/unit time (W/s) makes no sense at all. Watt-hours (watts times hours, not divided by hours) is a measure of energy. Watt-hours per unit time is, surprise, watts.

Energy output is quite *objective*. It's utility of that output is subjective but if you treat subjectivity as objectivity you end up with quite squishy results.

That's (at least) two variables, making it impossible to compare (intensity). Select temperature for effect and lumens for efficiency. Power out would be a better measure, though.
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All taken with due humility. We still need a way to judge the illumination we like. And that isn't easy to quantify.
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Of course it isn't. The eye is as bad at judging luminous intensity as the ear is at sound intensity. Too much depends on the environment and memory of these things is almost nonexistent.
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wrote:

Absolutely. Watts-out/watts-in gives efficiency directly. W/lumen gives a relative number but not as useful.
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But what does efficiency have to do with brightness? He may be technically correct, but how can a consumer tell what he is getting?
Say one bulb is 100 watts in, 65 watt out, it would be 65% efficient.
Another bulb is 50 watts in, 49 watts out, it would be more efficient, but not as bright. Isn't that where the lumens comes into play? Or candlepower?
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Visible energy out is the whole point of a light bulb, isn't it?

Ok...
Do you want a 49 watt out bulb or a 65 watt out bulb? If you only need 49W of illumination, certainly you would buy the smaller bulb.

Yes, but power is power (A candela is 4*pi*lumens ;-).
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A candela is 4*pi lumens for a uniformly even omnidirectional light source. A "MSCP" or "mean spherical candlepower" is 4*pi lumens.
A candela of anything more directional than "100% in all directions in all combinations of both ways of all 3 dimensions" is a different number of lumens, generally less since candela gets measured where the light goes.
Light sources that have greater directivity, greater concentration of their light into a specific direction, have higher ratio of candelas/lumens. The risk or downside from that is illumination being concentrated to an area smaller than what you want illuminated, or shortage of background illumination or overall "ambient illumination".
There are many people who don't work at 100% if illumination is restricted to some "task area".
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On Sun, 22 May 2011 01:05:07 +0000 (UTC), snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

That's how a lumen is defined, yes.

That's why they make reflectors.
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The poster said the EE stated efficiency was the determining factor. Therefore, he says the 49 watt output is what counts because it is more efficient. He states that lumens is not useful. I say BS.
This guy may be a genius, but cannot explain his theory to us commoners. Or a whole lot of fact was left out. I don't care how efficient a lamp is, if it is not bright enough, I'm getting a bigger one. More watts = more light.
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I read it as lumens didn't say anything about efficiency. Watts out does (since watts in is also stated). Lumens per watt means something but doesn't tell me anything about efficiency. 100W in, 3W out (about right for an incandescent) says it all.
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Lumens out per watt in varies widely among incandescents.
For example, a Sylvania 75W "standard" incandescent available at Lowes outshines a Sunbeam 100 watt one available at some dollar stores.
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snipped-for-privacy@manx.misty.com (Don Klipstein) wrote in

Yes, indeed. For incandescents my MO used to be: #1 go for the most lumens per watt. #2 for the top 3 or 4 compare life expectancy. Make your decision.
That was then. Recently things got more complicated because reliability of CFLs was initially rather poor and the price high. That's better now, but the advent of all kinds of different LEDs makes a real jumble out of all those comparisons, not to speak of the pricing problems. I did buy a 3 LED light for undercabinet over the counter lighting, and like the result (not the price): Utilitech 18" 3-Light Linking LED Bar, my price was $39.98, it is now $3 more on line at Lowe's
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On Sun, 22 May 2011 16:05:47 +0000 (UTC), snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

Of course it does! That's the whole point! Where did that come from?

So what?! That has *NOTHING* to do with the issue.
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This gets into difference between radiometric units and photometric units.
The difference between radiometric and photometric is that photometric takes into consideration the "photopic response" of a "standard human eyeball", as "determned" / defined by Commission International d'Eclairage (International Illumination Commission).
Watts radiated out by a lightbulb includes infrared and ultraviolet - useless.
Watts of visible light out may or may-not include a lot of nearly-useless wavelengths of nearly-ultraviolet or nearly-infrared.
Lumen rating is a fairly good indicator of as-seen-by-humans light output, when determined honestly.
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On Sun, 22 May 2011 00:31:29 +0000 (UTC), snipped-for-privacy@manx.misty.com (Don Klipstein) wrote:

Wrong. Watts *IN* includes everything.

...and is 100% meaningless to 99.99% of the population.
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wrote:

I was going to say my incandescent string is more like a 10-20 watt bulb. I would assume the led string is dimmer. It's probably also bluish, which to me defeats nice even warm lighting of the other. Maybe the OP is talking about a strip, didn't mention length. But he is likely long gone.
Greg
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