L.E.D. string lights

[Sam Takoy]

Hi,

What's the brightness (let's say per foot) of the L.E.D. rope lights in incandescent-light-watt-equivalent?

Thanks,

Sam

[Tony Hwang]

Hi, Watt is unit of power(energy) There is no such thing as ILWE.

[Ed Pawlowski]

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.

[Han]

Smitty Two wrote in news: [e-mail]:

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).

[RonB]

Cannot tell you what the brightness numbers are per foot. What is your application. We have used short runs pretty effectively in some museum display cases where we wanted indirect lights. It is best to keep them out of sight with simple baffles.

RonB

[krw]

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.

[krw]

Absolutely. Watts-out/watts-in gives efficiency directly. W/lumen gives a relative number but not as useful.

[Han]

Smitty Two wrote in news:prestwhich- [e-mail]:

Sure can, but is it specified then that infrared (heat) and (possibly) UV radiation is included or excluded in those watts? Also, I believe that those light outputs in watts are even less in consideration of the subjective "feel" of the light.

[Ed Pawlowski]

wrote in

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?

[Han]

" [e-mail]" wrote in news: [e-mail]:

All taken with due humility. We still need a way to judge the illumination we like. And that isn't easy to quantify.

[aemeijers]

Depends on brand and color and how many LEDs per foot. I've seen dim ones that looked like theater/airplane escape lighting, and ones bright enough to put over crown molding high on the wall, and use for indirect room lighting. They're pretty cheap- buy a string and play with it.

[krw]

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 ;-).

[krw]

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.

[Don Klipstein]

I look at the lumens.

As a result, I know that most dollar store 100W incandescents produce about the same amount of light as 75W "standard" incandescents. And that dollar store 75W incandescents tend to not outshine 60-watters worth buying. And, that superlonglife vibration-resistant 3500 or 5,000 hour rated 75 or 100W incandescents hardly outshine "one wattage lower" of "standard" incandescents. (That is 60 or 75 watts respectively.) Decreasing electricity consumption by 15-25 watts often easily pays for cost of buying more lightbulbs, when one has a need for incandescents.

Stock up on shorter-life higher-efficiency versions of incandescents

*with good lumen figures* while you can, if you have a need for incandescents. Exempted from the upcoming USA ban are less-efficient shock/vibration-resistant and "traffic signal" versions, along with many others such as most under 25 or over 150 watts, all having "design voltage" outside the 110-130 volt range, all having a base other than right-hand-screw of E26/E27 size, and a few others exempted on basis of shape, size or color of the bulb.

There are minimum lumen standards for Energy Star rated non-incandescent lightbulbs:

40W equivalent - at least 400 lumens 60W equivalent - at least 800 lumens 75W equivalent - at least 1100 lumens 100W equivalent - at least 1600 lumens

150W equivalent - at least 2600 lumens (IIRC)

"Better" 120V incandescents have lumens in these ranges, & these lumens/watt:

15W - 108 to 126 lumens (life expectancy 2500 hours) 7.2-8.4

25W - 180 to 210 lumens (life expectancy 1000 or 1500 hours) 7.2-8.4

40W - 440 to 505 lumens (life expectancy 1000 or 1500 hours) 11 - 12.6 60W - 840 to 890 lumens (life expectancy 1000 hours) 12 - 14.8 75W - 1150 to 1210 lumens (life expectancy 750 hours) 15.3- 16.1 100W - 1670 to 1750 lumens (life expectancy 750 hours) 16.7- 17.5

150W - 2800 to ~2920 lumens (life expectancy 750 hours) 18.7-19.5

200W - 3800 to ~3980 lumens (life expectancy 750 hours) 19.0-19.9

300W - 6100 to 6300 lumens (life expectancy 750 hours) 20.3 - 21

[Don Klipstein]

Lasers tend to be rated in watts of output.

This has only very rough correlation with lumens of output.

Output watts or milliwatts are "radiometric", meaning power, or energy per unit time.

Lumens are "photometric", which takes into consideration a "standard human eyeball"'s "photopic" spectral response.

One watt of 555 nm yellowish green light is 683 lumens. But, one watt of 632.8 nm red is about 163 lumens, and 1 watt of 650 nm red is 73 lumens.

1 watt of 685 nm (a longer deep red wavelength of some early visible laser diodes) is a mere 8 lumens. 1 watt of 405 nm violet is a little over 3 lumens, but looks brighter than that to "night vision" (favoring shorter visible wavelengths) and causes many fluorescent objects to fluoresce with as much as 100's of lumens (theoretical limit of 500).

One watt of 532 nm, a common more-luminous green laser wavelength, is

604 lumens. Get a 532 nm laser pointer when you need the most brightness from the 4.9999 milliwatt limit of Class IIIa - at that wavelength, 4.99 milliwatts is 3 lumens.

One watt of invisible infrared or invisible ultraviolet has zero lumens.

Watt or milliwatt figures for laser output have fairly good correlation with ability to cause burns, including to irreplaceable photosensors in the eyes. Lumens has less correlation, since different wavelengths have greatly different lumens for same watts or milliwatts.

===========

Output of lasers is usually rated in *radiometric* units, as in watts or milliwatts. Output of lightbulbs is usually rated in *photometric* units, as in lumens.

[Don Klipstein]

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.

[Don Klipstein]

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".

[zek]

Radiance is the correct term for total light output. Lumens is an amount hitting a surface at a particular point. Add a lens and the Lumens will increase at some point. add a reflector and Lumens increase at some point. A flashlight hAs high lumens in a spot. When I start reading about candlepower, I start to get a headache.

Greg

[krw]

That's how a lumen is defined, yes.

That's why they make reflectors.

[zek]

There must be some kind od standard rating Lumens, because it's all about distance, like 100lumens at one meter or foot. The farther away the light, the lumens goes down since lumens is the amount falling on a surface from a light. Candle power is light output looking at the source of the light.

Greg Greg