LEDs as lamp replacements
 

Lostgallifreyan wrote:

(Don Klipstein) wrote

There are some high power IR laser diodes more efficienct than LPS.
Other than those, laser diodes are less efficient than most sodium lamps.

Ok. I thought more laser diodes were but never mind.. Aren't most class 3B
visible red diodes around 20% efficient or more though? That still leaves a
lot of headroom. Tungsten is often said to be 1% to 2% efficient at making
visible light.

Wikipedia says 2.6% for the ubiquitous 100W tungsten filament bulb and 3.5% for
quartz halogen.
http://en.wikipedia.org/wiki/Luminous_efficacy


Graham

LEDs as lamp replacements
 

On 2007-07-09, Eeyore wrote:

In any case don't 'white leds' use the same phosphor method of producing light
that CFLs do ?

some have yellow fluorescent dye and a blue LED die, it's sort of the
same, but I think the fluorescent lamp has a better spectrum.

Bye.
Jasen

LEDs as lamp replacements
 

"Eeyore" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

MrT.

LEDs as lamp replacements
 

In article ,
Mr.T MrT@home wrote:

"Eeyore" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

Most domestic lighting is used after dark and the colour temperature last
thing in the day is nothing like 4500k.

--
*I never drink anything stronger than gin before breakfast *

Dave Plowman London SW
To e-mail, change noise into sound.

LEDs as lamp replacements
 

"Mr.T" MrT@home wrote in message
...

"Eeyore" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

Daylight for artificial lighting is rather annoying. Maybe humans have
been conditioned to want warmer lighting at night, after 10s of
thousands of years of getting by with fire as light source at night.

I find the 3000K of my CFLs to be barely warm enough.

Bert

LEDs as lamp replacements
 

Eeyore wrote in
:

Wikipedia says 2.6% for the ubiquitous 100W tungsten filament bulb

For a 110V type at 1700 lumens, perhaps. 240V types only put 1200 lumens.

LEDs as lamp replacements
 

Eeyore wrote in
:

I've yet to see a spectrum published for those 'white' leds. I assume
it must be similar to CFLs.


?
That Cree document I cited has extensive detail. Several graphs for various
types. Also, they do a 'binning and labelling' document that shows plots of
all types on a cromaticity diagram. I had to think a bit to work out where
my LED torch was on that, but it's all there.

LEDs as lamp replacements
 

"Dave Plowman (News)" wrote in
:

Most domestic lighting is used after dark and the colour temperature last
thing in the day is nothing like 4500k.


No. It's akmost certainly much hotter. While it's at its lowest brightness,
the light of a clear day fading is biased extremely toward blue. The rods
in the eye make use of that, it's why greens and blues look brighter than
red flower petals at twilight.

LEDs as lamp replacements
 

Eeyore wrote in
:

CFLs already include those losses in their stated power. LED fans only
ever quote the DC input power required for the 'chip'.

Talk about an uneven playing field !


Not their fault, exactly. CFL's rarely come without a supply attached now.
Also, LED of this kind are new, very few complete lamps with supplies exist
yet, compared to CFL's. Also, LED's run on a very different range of
supplies. Try running any fluorescent tube off a battery and a resistor.
LED's have a modularity that makes it sensible to specify them directly.

If you want to know the total power, it's not the LED maker's job to
specify any PSU they're not making themselves. You need to look at what
PSU's are available. It's only two specs for power conversion efficiency to
consider. Small inconvenience compared to what's gained.

LEDs as lamp replacements
 

In article , "Albert Manfredi" wrote:
"Mr.T" MrT@home wrote in message
u...

"Eeyore" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

Daylight for artificial lighting is rather annoying. Maybe humans have
been conditioned to want warmer lighting at night, after 10s of
thousands of years of getting by with fire as light source at night.

Not only that, but pinpoint sources of light have glare. Daylight is dispersed.

greg


I find the 3000K of my CFLs to be barely warm enough.

LEDs as lamp replacements
 

LEDs as lamp replacements
 

Albert Manfredi wrote:

"Mr.T" MrT@home wrote in message
...


"Eeyore" wrote in message
...

4500K is still somewhat blue for most peoples' taste.


You must really hate daylight then!


Daylight for artificial lighting is rather annoying.

snip

For some of us in cold climates with little daylight during the winter
season, seasonal affective disorder can be a serious problem; bright
daylight wavelength lighting at night and in the morning is necessary
as a therapy.

BTW, why is this thread crossposted to so many newsgroups? I suggest
removing r.a.t., s.e.b. and s.e.t.a. at least for followups.

Regards,

Michael

LEDs as lamp replacements
 

In article , Lostgallifreyan wrote:
(Don Klipstein) wrote in
:

There are some high power IR laser diodes more efficienct than LPS.
Other than those, laser diodes are less efficient than most sodium lamps.

Ok. I thought more laser diodes were but never mind.. Aren't most class 3B
visible red diodes around 20% efficient or more though? That still leaves a
lot of headroom. Tungsten is often said to be 1% to 2% efficient at making
visible light. So a 100W incandescent 17 l/W at 1% to 2%

More like 6-7%. Each watt of tungsten radiation in the 400-700 nm range
is around 250 lumens.

places the Cree XR-E's 50+ l/W at 3 times that, up to 6%.

Figure around 250-300 lumens per watt of "white LED light". Looks like
those achieve about 20%.

683 lumens in a watt of light only applies for a wavelength around 555
nanometers, where the human eye's photopic sensitivity is highest. For
other wavelengths, multiply 683 by the "photopic function".

These are loose figures but they
suggest that if LED's reach efficiencies like DVD writer diodes, maybe 3 to
4 times the current efficiency can be had. (Not including phosphor losses,
but including LED driver losses). These figures are assuming Imax, 1A per
emitter, if LED's become cheap enough to double the emitter count and drive
each at 500 mA, the efficiency will go up by 50% or more.

- Don Klipstein )

LEDs as lamp replacements
 

In article , Mr.T wrote:

"Eeyore" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

At usual room illuminating levels in most rooms in most homes, lamps
that match the color of daylight tend to make things somewhat dreary - no
matter what the color rendering index, although higher CRI and any color
distortions being in the "more vivid" direction (common with triphosphor
fluorescents CRI 82-86) tend to help.

"Cool White" fluorescent is 4100-4300 K, generally nominally 4100.

- Don Klipstein )

LEDs as lamp replacements
 

In article , Eeyore wrote:


Don Klipstein wrote:

Eeyore wrote:

The normal home doesn't have DC. What do you use for current limiting
and how much power does that dissipate ?

Electronic ballasts for fluorescent lamps (including the ones in all
spiral and most other screw base CFLs) require DC, so require conversion
of AC to DC, and for that matter back to AC of a higher frequency. Many
of those don't have huge losses, in fact usually less loss than iron core
inductive ballasts.

I was asking about LED drivers not CFLs.

CFLs already include those losses in their stated power. LED fans only ever quote the DC
input power required for the 'chip'.

Talk about an uneven playing field !

Linear fluorescents also have nominal wattages not including ballast
losses. Though ballasts for 17 and 32 watt T8 ones and 20 watt T12
ones mostly tend to underpower them a little and fixtures for those tend
to draw close to nominal lamp wattage with ballast losses included.
Same is true with many 22 watt circlines. However, this is not true for
most other linear fluorescents such as most 34 and 40 watt T12 and 15 watt
T8, circlines other than 22 watts, all common wattages 13 watts or less,
30 watt 3-footers, and I think also the new T5 sizes over 13 watts.

- Don Klipstein )

LEDs as lamp replacements
 

In article , Eeyore wrote:

Don Klipstein wrote:

Don Pearce wrote:

Currently, white LEDs are in fact blue LEDs coated with a fluorescent
substance, so probably the overall light quality will be quite similar
to CFL.

Actually, it's more like that of somewhere between a "cool white" and a
"daylight" old-fashioned fluorescent, with similar color distortions.
There are now some warmer white and higher color rendering index white
LEDs.

I've yet to see a spectrum published for those 'white' leds. I assume it
must be similar to CFLs.

Nichia's NSPW500BS, their longstanding 5 mm white model:
http://www.nichia.com/specification/...SPW500BS-E.pdf

Nichia's NS6W083, a higher power LED:
http://www.nichia.com/specification/...NS6W083T-E.pdf

Lumileds Luxeon K2:
http://www.lumileds.com/pdfs/DS51.pdf

Cree X
http://www.cree.com/products/pdf/XLamp7090XR-E.pdf

- Don Klipstein )

LEDs as lamp replacements
 

LEDs as lamp replacements
 

In article , Lostgallifreyan wrote:
(Don Klipstein) wrote in
:

Ok. I thought more laser diodes were but never mind.. Aren't most
class 3B visible red diodes around 20% efficient or more though? That
still leaves a lot of headroom. Tungsten is often said to be 1% to 2%
efficient at making visible light. So a 100W incandescent 17 l/W at 1%
to 2%

More like 6-7%. Each watt of tungsten radiation in the 400-700 nm
range
is around 250 lumens.


So why do Cree, and Wikipedia, and probably many others, cite only 17 l/W?
Every time I've seen the efficiency expressed as a percentage it's been '1
to 2%'. Wikipedia state 2.6% which is a tad higher than I've ever been told
before, and even that's nowhere near 6-7%! It's not going to be easy to
learn if everywhere I turn there are figures differing by factors of three
or more. What makes all the others I've seen wrong?

I have a homebrew BASIC program with the blackbody function and the
photopic function.

A USA-usual "Big-3" brand 100W 120V "standard frost" or clear
incandescent rated 750 hours average life and with a coiled-coil filament
is rated to produce 1710-1750 lumens, traditionally 1710. (The "Soft
White" version achieves 40 lumens less.)
The color temperature of that one is 2865 K.

My homebrew program says 16.7 lumens per watt (pretty close) and that
6.63% of the radiation is in the 400-700 nm range (the usual definition of
visible light). It assumes an ideal blackbody radiator with all energy
outgo being radiation.

The discrepancy is caused by tungsten having emissivity varying with
wavelength - generally inversely. Infrared radiation is suppressed enough
to get 17.1 lumens/watt instead of 16.7 despite the lamp having some heat
conduction loss. (For that matter, color temperature does not exactly
match filament temperature - filament temperature is slightly lower.)

So an ideal blackbody at 2865 K receiving 100 watts and radiating 100%
of this produces 6.63 watts of visible light and 1670 lumens. The ratio
of lumens to watts of visible output is 252, not 683.
683 lumens in a watt of visible light is only true for yellow-green
light of wavelength around 555-556 nanometers, where this figure is
maximized. Those saying that incandescents are only around 2% efficient
are assuming that a watt of any kind of visible light has 683 lumens.

Assuming my 252 lumens per watt figure for the visible portion of 2865K
blackbody radiation is true for a 1710 lumen 100 watt lightbulb, that
means a 1710 lumen 100 watt lightbulb is about 6.8% efficient at
converting electrical power to visible light (400-700 nm). The truth
won't be far from this.

- Don Klipstein )

LEDs as lamp replacements
 

"Dave Plowman (News)" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

Most domestic lighting is used after dark and the colour temperature last
thing in the day is nothing like 4500k.

By that reasoning you should really match the color temperature of
moonlight, which is greater than 4500K.

MrT.

LEDs as lamp replacements
 

On Wed, 11 Jul 2007 18:39:36 +1000, "Mr.T" MrT@home wrote:


"Dave Plowman (News)" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

Most domestic lighting is used after dark and the colour temperature last
thing in the day is nothing like 4500k.

By that reasoning you should really match the color temperature of
moonlight, which is greater than 4500K.

MrT.


Nice chart here

http://www.olympusmicro.com/primer/l...colortemp.html

d
--
Pearce Consulting
http://www.pearce.uk.com

LEDs as lamp replacements
 

"Albert Manfredi" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

Daylight for artificial lighting is rather annoying. Maybe humans have
been conditioned to want warmer lighting at night,

Conditioned, exactly!
Conditioning can be changed, I far prefer daylight lamps. But it does depend
on the application.

I find the 3000K of my CFLs to be barely warm enough.

Fine, that's why we all get a personal preference. However the spectrum
spread has as much to do with it as the stated color temperature IMO.

MrT.

LEDs as lamp replacements
 

"GregS" wrote in message
...
Not only that, but pinpoint sources of light have glare.

I think you will find enough glare from reflections during daylight hours.
That's generally the greatest need for sunglasses after all.

Daylight is dispersed.

Not very dispersed on a cloudless day though.

MrT.

LEDs as lamp replacements
 

(Don Klipstein) wrote in
:

So an ideal blackbody at 2865 K receiving 100 watts and radiating 100%
of this produces 6.63 watts of visible light and 1670 lumens. The ratio
of lumens to watts of visible output is 252, not 683.
683 lumens in a watt of visible light is only true for yellow-green
light of wavelength around 555-556 nanometers, where this figure is
maximized. Those saying that incandescents are only around 2% efficient
are assuming that a watt of any kind of visible light has 683 lumens.


This makes sense, in a way, though the actual assumption is surely a
misinterpretation. In the context of lasers it makes sense now, because
those are usually monochromatic (or take pumping on narrow bands of lines),
and the maximum efficiency of any 'line' drawn from that lamp will be
around 2% at best. Discussions of efficiency for narrow bands or lines in
lasers or LED's or phosphor or sodium sources dominate a lot of reference
material, so that's probably why this figure arises so often.

Even so, it's harder to see how that hasn't been corrected in something
like Wikipedia by now. I guess a lot of people don't think of light below
670 nm as useful? (If you look at colours on a monitor or TV you can cut
all below about 635 nm). http://www.inchem.org/documents/ehc/ehc/e23_3.gif
shows a diagram that suggests you might lose 25% or so from a 3000K
tungsten emission just by ignoring a big enough chunk of deep red. (More
lost that way than gained by IR supression in tungsten). Still doesn't
explain the 2.6% value on Wikipedia, but if only the dominant 'line' is
taken that wouldn't either because 2.6% would probably be too high, even
for a 110V 100W incandescent.

A lot of the heat energy is carried to the bulb by convection and emitted
as IR, so the temperature will be lower than than if the filament was
heated in vaccuum. It's not an ideal blackbody radiator. That could make a
likely average fall well below 6%, especially if you consider that the
world has a lot of 240V lamps too. The steepness of that curve alone is
enough to make large changes in output of visible lumens with small changes
in voltage.

In short, I guess that the figure of 2.6% and others similar might not have
been gained by calculation at all, but by measurement. I don't know what
the conditions for that were though, so I can't comment on them.

LEDs as lamp replacements
 

In article ,
Mr.T MrT@home wrote:

"Dave Plowman (News)" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

Most domestic lighting is used after dark and the colour temperature
last thing in the day is nothing like 4500k.

By that reasoning you should really match the color temperature of
moonlight, which is greater than 4500K.

Provided you also match the intensity? ;-)

The eye accommodates gradually to a change in colour temperature. It
doesn't look 'cold' to us at midday and 'warm' in the evening. But does
notice a sudden change in that colour temperature - hence its importance
for film and video etc.

Lighting which is used to replace daylight - like that most of us have at
home for use when daylight fades - ideally shouldn't give such a sudden
change in temperature that it is noticeable. In the same way as lighting
used to supplement daylight - like in say an office - should also be an
approximate match to that daylight. It's common sense, really.

--
*Never test the depth of the water with both feet.*

Dave Plowman London SW
To e-mail, change noise into sound.

LEDs as lamp replacements
 

"Mr.T" MrT@home wrote in
u:

Fine, that's why we all get a personal preference. However the spectrum
spread has as much to do with it as the stated color temperature IMO.


Yes. We are better at sensing discontinuities too, than we might think. We
can fool vision with RGB but when presented with purple and monochrome
violet we can see the difference without difficulty. Same goes for the
orange of laser or LED or low pressure sodium, or that made by mixing red
and green. We usually know when we're seeing a pure form of colour, and
it's only conditioning that allows us to easily accept things like TV
screens. (Which chop out all red below about 635 nm, as it happens, as
well as most of the rest of the spectrum).

As far as natural light goes, we are best satisfied by a true continuum
because we adapted to that before we evolved eyes, as such. Take a look at
a Cree or Luxeon LED carefully reflected in a CD. Now do the same with a
CFL. The LED's might be a tad skewed in their distribution but so is
daylight, usually, and LED's make a much better continuum than CFL's do. If
CFL's could do better they probably would, but I haven't seen one that
does.

LEDs as lamp replacements
 

On Wed, 11 Jul 2007 10:55:43 +0100, "Dave Plowman (News)"
wrote:

In article ,
Mr.T MrT@home wrote:

"Dave Plowman (News)" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

Most domestic lighting is used after dark and the colour temperature
last thing in the day is nothing like 4500k.

By that reasoning you should really match the color temperature of
moonlight, which is greater than 4500K.

Provided you also match the intensity? ;-)

The eye accommodates gradually to a change in colour temperature. It
doesn't look 'cold' to us at midday and 'warm' in the evening. But does
notice a sudden change in that colour temperature - hence its importance
for film and video etc.


It is more complicated than that. If a cloud suddenly covers the sun,
we don't perceive a change in colour temperature. But if that happens
while filming, the colour change is obvious and intrusive. The thing
is that we are used to the normal interactions with the real world and
respond to all sorts of cues in our surroundings to make instant
adjustments. When sitting indoors watching TV, those cues are not
there, so we can't make the adjustments.

Lighting which is used to replace daylight - like that most of us have at
home for use when daylight fades - ideally shouldn't give such a sudden
change in temperature that it is noticeable. In the same way as lighting
used to supplement daylight - like in say an office - should also be an
approximate match to that daylight. It's common sense, really.

I once bought a "daylight" bulb with a bright blue tint, thinking it
would be better than normal bulbs. It was back in its box within a
day. Lower colour temperatures are now what we consider right for the
evening. The same goes for any indoor lighting - approaches to
daylight for indoor lighting are always received poorly.

d

--
Pearce Consulting
http://www.pearce.uk.com

LEDs as lamp replacements
 

"Dave Plowman (News)" wrote in message
...
The eye accommodates gradually to a change in colour temperature. It
doesn't look 'cold' to us at midday and 'warm' in the evening. But does
notice a sudden change in that colour temperature

Yes.

- hence its importance for film and video etc.

That's more to do with the relative sensitivity of film color layers etc.
They are specifically balanced for Daylight or Tungsten, and are wildly
innacurate when used with the wrong light source.

Lighting which is used to replace daylight - like that most of us have at
home for use when daylight fades - ideally shouldn't give such a sudden
change in temperature that it is noticeable.

It only takes a few minutes for the eyes to adjust.

In the same way as lighting
used to supplement daylight - like in say an office - should also be an
approximate match to that daylight.

Many internal offices get NO daylight, only artificial light. Why would it
matter if it's day or night outside?

It's common sense, really.

Only if you realise that's an oxymoron.

MrT.

LEDs as lamp replacements
 

"Don Pearce" wrote in message
...
approaches to
daylight for indoor lighting are always received poorly.

No argument there, people ARE conditioned to incandescent lights at night,
at the moment.
(which of course are not so different to the lamps and candles that came
before.)
I wonder whether that will be so a hundred years from now though, when very
few people will even remember seeing one. Whether we will always demand to
emulate what we now have, or whether we will accept a gradual change to
something else, IF it is more efficient.
And of course the eyes sensitivity is not it's highest at the red end
either.

MrT.

LEDs as lamp replacements
 

On Wed, 11 Jul 2007 20:48:07 +1000, "Mr.T" MrT@home wrote:


"Don Pearce" wrote in message
...
approaches to
daylight for indoor lighting are always received poorly.

No argument there, people ARE conditioned to incandescent lights at night,
at the moment.
(which of course are not so different to the lamps and candles that came
before.)
I wonder whether that will be so a hundred years from now though, when very
few people will even remember seeing one. Whether we will always demand to
emulate what we now have, or whether we will accept a gradual change to
something else, IF it is more efficient.
And of course the eyes sensitivity is not it's highest at the red end
either.

MrT.


Just thought. Some friends of mine have a house in America with a
bathroom right in the centre, which has no windows. They had one of
those sun tubes fitted that brings daylight down from the roof. The
response from guests is always the same. "Why do you have a blue light
in the bathroom?"

d

--
Pearce Consulting
http://www.pearce.uk.com

LEDs as lamp replacements
 

In article ,
Don Pearce wrote:
I once bought a "daylight" bulb with a bright blue tint, thinking it
would be better than normal bulbs. It was back in its box within a
day. Lower colour temperatures are now what we consider right for the
evening. The same goes for any indoor lighting - approaches to
daylight for indoor lighting are always received poorly.

I have daylight fluorescent lighting in my home workshop which also has a
degree of natural lighting. Wouldn't have any other.

--
*Preserve wildlife - Go pickle a squirrel*

Dave Plowman London SW
To e-mail, change noise into sound.

LEDs as lamp replacements
 

On Wed, 11 Jul 2007 11:58:56 +0100, "Dave Plowman (News)"
wrote:

In article ,
Don Pearce wrote:
I once bought a "daylight" bulb with a bright blue tint, thinking it
would be better than normal bulbs. It was back in its box within a
day. Lower colour temperatures are now what we consider right for the
evening. The same goes for any indoor lighting - approaches to
daylight for indoor lighting are always received poorly.

I have daylight fluorescent lighting in my home workshop which also has a
degree of natural lighting. Wouldn't have any other.

Workshops are a different thing - they aren't really a domestic
environment. And when mixed with natural daylight, I can see the
point.

d
--
Pearce Consulting
http://www.pearce.uk.com

LEDs as lamp replacements
 

In article ,
Mr.T MrT@home wrote:

"Dave Plowman (News)" wrote in message
...
The eye accommodates gradually to a change in colour temperature. It
doesn't look 'cold' to us at midday and 'warm' in the evening. But does
notice a sudden change in that colour temperature

Yes.

- hence its importance for film and video etc.

That's more to do with the relative sensitivity of film color layers etc.
They are specifically balanced for Daylight or Tungsten, and are wildly
innacurate when used with the wrong light source.

In which way are they 'inaccurate'? They will look wrong to the eye on a
'cut' but as with real life if all shots are matched the eye will
accommodate. The monitor you're reading this on is unlikely to match
*exactly* another one in colour temperature but will look ok to the
individual. The eye compensates, as I said, as it must do given that
daylight changes. Unless it has a reference to match to.

Lighting which is used to replace daylight - like that most of us
have at home for use when daylight fades - ideally shouldn't give such
a sudden change in temperature that it is noticeable.

It only takes a few minutes for the eyes to adjust.

Err, yes. That's what I said. But it doesn't react instantly. Hence it
notices a sudden change in colour temperature. Like switching on 4500K
lights in a house when it gets dark.;-)

In the same way as lighting
used to supplement daylight - like in say an office - should also be an
approximate match to that daylight.

Many internal offices get NO daylight, only artificial light. Why would
it matter if it's day or night outside?

Sigh. Same as a house then. If you live underground...

It's common sense, really.

Only if you realise that's an oxymoron.

Have you never wondered why most prefer the colour temperature of tungsten
for domestic lighting?

--
*If I worked as much as others, I would do as little as they *

Dave Plowman London SW
To e-mail, change noise into sound.

LEDs as lamp replacements
 

In article ,
Mr.T MrT@home wrote:
No argument there, people ARE conditioned to incandescent lights at
night, at the moment. (which of course are not so different to the lamps
and candles that came before.)

You've never seen gaslight, then?

--
*When the going gets tough, use duct tape

Dave Plowman London SW
To e-mail, change noise into sound.

LEDs as lamp replacements
 

In article ,
Don Pearce wrote:
On Wed, 11 Jul 2007 11:58:56 +0100, "Dave Plowman (News)"
wrote:

In article ,
Don Pearce wrote:
I once bought a "daylight" bulb with a bright blue tint, thinking it
would be better than normal bulbs. It was back in its box within a
day. Lower colour temperatures are now what we consider right for the
evening. The same goes for any indoor lighting - approaches to
daylight for indoor lighting are always received poorly.

I have daylight fluorescent lighting in my home workshop which also has a
degree of natural lighting. Wouldn't have any other.

Workshops are a different thing - they aren't really a domestic
environment.

Mine is. ;-) It is really a bedroom.

And when mixed with natural daylight, I can see the
point.

Quite. Good domestic lighting supplements or replaces that provided by
god. ;-)

--
*Xerox and Wurlitzer will merge to market reproductive organs.

Dave Plowman London SW
To e-mail, change noise into sound.

LEDs as lamp replacements
 

In article , Mr.T wrote:

"Dave Plowman (News)" wrote in message
...
4500K is still somewhat blue for most peoples' taste.

You must really hate daylight then!

Most domestic lighting is used after dark and the colour temperature last
thing in the day is nothing like 4500k.

By that reasoning you should really match the color temperature of
moonlight, which is greater than 4500K.

Moonlight's color temperature at its highest is about 4000. It is
usually even less. It is less than that of sunlight because the moon is
not white or gray, but brownish.

Meanwhile, at illumination level so low that color vision does not work
well, color temperature matters less. At illumination levels an order of
magnitude or two or three above that of moonlight, most people like it
warm (lower color temperature).

- Don Klipstein )

LEDs as lamp replacements
 

In article , Mr.T wrote:

"Don Pearce" wrote in message
...
approaches to
daylight for indoor lighting are always received poorly.

No argument there, people ARE conditioned to incandescent lights at night,
at the moment.
(which of course are not so different to the lamps and candles that came
before.)
I wonder whether that will be so a hundred years from now though, when very
few people will even remember seeing one. Whether we will always demand to
emulate what we now have, or whether we will accept a gradual change to
something else, IF it is more efficient.
And of course the eyes sensitivity is not it's highest at the red end
either.

Lumens per watt of the portion of blackbody radiation that is in the
400-700 nm range is maximized in the upper 3,000's at about 263 lumens per
visible radiated watt. Apparently, getting into the 5,000's K causes blue
content to increase faster than red content decreases, decreasing the
percentage of the visible light spectral content that is in the
yellow-green range.

This figure is down about 1% at around 3300 and around 4600 K. There is
a lot of freedom in color temperature of a whitish artificial light source
without compromising luminous efficacy much.

- Don Klipstein )

LEDs as lamp replacements
 

In article , Dave Plowman (News) wrote:
In article ,
Mr.T MrT@home wrote:
No argument there, people ARE conditioned to incandescent lights at
night, at the moment. (which of course are not so different to the lamps
and candles that came before.)

You've never seen gaslight, then?

Correlated color temperature generally mid 3,000's, and sometimes looks
a bit cold and spookyish. It's also a bit greener than light from a
blackbody, but usually looks only slightly so in my experience.

- Don Klipstein )

LEDs as lamp replacements
 

In article , Dave Plowman (News) wrote:

Have you never wondered why most prefer the colour temperature of tungsten
for domestic lighting?

Personally, I like more like 3500K at most brighter indoor lighting
levels, closer to 3,000 for dimmer indoor lighting.

Higher color temperature often appears "dreary" unless illumination
level is very high.

People often find it "dreary" outdoors under overcast conditions with
color temperature around 6000 K, especially when illumination level gets
under several thousand lux.

Things can look dreary at dusk and dawn, though people can be in a less
dreary mood outdoors then. At dawn things are brightening, and at dusk
people are likely to be on their way home from work or towards
entertaining activities.

As for why higher color temperature can make things "drearier" at lower
illumination levels:

1. The spectrum is richer in wavelengths favorable to scotopic vision,
which lacks ability to see color. Higher color temperature favors things
looking grayish when illumination level is down to several lux or less.

2. More light of wavelengths favorable to scotopic vision can make your
eye's pupil smaller than otherwise for a given illumination level. 100
lux at 5000 K can make your pupil smaller than 100 lux at 3000 K. (The
lux and other photometric units are defined in terms of photopic vision
and not scotopic vision.) That can make things appear dimmer. This can
also have an effect on color vision if illumination level is down to a few
lux or less, by depriving the color-sensing cones of light.

3. Reds look darker at higher color temperature, and can "drop out to
black" when color temperature is high and illumination level is low enough
to start making photopic vision marginal.

- Don Klipstein )

LEDs as lamp replacements
 

In , Lostgallifreyan wrote:
(Don Klipstein) wrote in
:

So an ideal blackbody at 2865 K receiving 100 watts and radiating 100%
of this produces 6.63 watts of visible light and 1670 lumens. The ratio
of lumens to watts of visible output is 252, not 683.
683 lumens in a watt of visible light is only true for yellow-green
light of wavelength around 555-556 nanometers, where this figure is
maximized. Those saying that incandescents are only around 2% efficient
are assuming that a watt of any kind of visible light has 683 lumens.


This makes sense, in a way, though the actual assumption is surely a
misinterpretation. In the context of lasers it makes sense now, because
those are usually monochromatic (or take pumping on narrow bands of lines),
and the maximum efficiency of any 'line' drawn from that lamp will be
around 2% at best. Discussions of efficiency for narrow bands or lines in
lasers or LED's or phosphor or sodium sources dominate a lot of reference
material, so that's probably why this figure arises so often.

Even so, it's harder to see how that hasn't been corrected in something
like Wikipedia by now. I guess a lot of people don't think of light below
670 nm as useful? (If you look at colours on a monitor or TV you can cut
all below about 635 nm). http://www.inchem.org/documents/ehc/ehc/e23_3.gif
shows a diagram that suggests you might lose 25% or so from a 3000K
tungsten emission just by ignoring a big enough chunk of deep red. (More
lost that way than gained by IR supression in tungsten). Still doesn't
explain the 2.6% value on Wikipedia, but if only the dominant 'line' is
taken that wouldn't either because 2.6% would probably be too high, even
for a 110V 100W incandescent.

Wikipedia articles are written by anyone who wants to write them, and
with a few exceptions can be edited by anyone who wants to go in and edit
them - anonymously even, without even creating an account and signing in.

A lot of the heat energy is carried to the bulb by convection and emitted
as IR, so the temperature will be lower than than if the filament was
heated in vaccuum.

It's not an ideal blackbody radiator. That could make a
likely average fall well below 6%, especially if you consider that the
world has a lot of 240V lamps too.

Tungsten deviates from blackbody largely by some supression of infrared,
enough to slightly outweigh heat conduction and convection by the fill gas
in some incandescents.

I think 240V 1000 hour 100 watt would be more like about 5.5%.

15 watt 120V 2500 hour incandescent, at 8 lumens/watt and color temp.
2400K at most, is close to 3%.

The steepness of that curve alone is enough to make large changes in
output of visible lumens with small changes in voltage.

Yes, quite true. But at full voltage most 120V incandescents 60 watts
or more are about 4.5-8% efficient at converting electricity to radiation
in the 400-700 nm range.

In short, I guess that the figure of 2.6% and others similar might not have
been gained by calculation at all, but by measurement. I don't know what
the conditions for that were though, so I can't comment on them.

- Don Klipstein )

LEDs as lamp replacements