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.
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).
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
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.
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
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 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".
- Don Klipstein ( email@example.com)
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.
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.
firstname.lastname@example.org (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
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
This gets into difference between radiometric units and photometric
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 -
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 ( email@example.com)
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.
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