I seem to remember reading this somewhere. Can anyone tell me if it's
true or not?

Hugh

--

Hugh Newbury

www.evershot-weather.org

On 12/09/2014 08:49, Hugh Newbury wrote:

I seem to remember reading this somewhere. Can anyone tell me if it's
true or not?

If you stare at the actual bare illuminated LED die from point blank
range it's visible output is about equivalent to the surface brightness
of the sun. It doesn't have much thermal or UV component but it really
isn't good to look at. Same issue with staring into a laser pointer.

If you are using bare LEDs they come with warnings not to look directly
at them (which are largely unnecessary since it is painful to do it).

Once the light is diffused it is just light like any other although the
colour rendering is a bit poor (though nowhere near as bad as CFLs).

--
Regards,
Martin Brown

On 12/09/2014 09:02, Martin Brown wrote:
On 12/09/2014 08:49, Hugh Newbury wrote:

I seem to remember reading this somewhere. Can anyone tell me if it's
true or not?

If you stare at the actual bare illuminated LED die from point blank
range it's visible output is about equivalent to the surface brightness
of the sun. It doesn't have much thermal or UV component but it really
isn't good to look at. Same issue with staring into a laser pointer.

If you are using bare LEDs they come with warnings not to look directly
at them (which are largely unnecessary since it is painful to do it).

Once the light is diffused it is just light like any other although the
colour rendering is a bit poor (though nowhere near as bad as CFLs).

And there are people who suffer the effects of any form of fluorescent
lamp such as getting skin and eye problems. Those with macular
degeneration are sometimes advised to wear yellow glasses outdoors to
reduce the impact of blue light (and, I assume, any UV).

Maybe, for some, LEDs are better than fluorescents and even quartz
lamps? (Or perhaps that should be "some LEDS"?)

--
Rod

On 12/09/2014 09:26, polygonum wrote:
On 12/09/2014 09:02, Martin Brown wrote:
On 12/09/2014 08:49, Hugh Newbury wrote:

I seem to remember reading this somewhere. Can anyone tell me if it's
true or not?

If you stare at the actual bare illuminated LED die from point blank
range it's visible output is about equivalent to the surface brightness
of the sun. It doesn't have much thermal or UV component but it really
isn't good to look at. Same issue with staring into a laser pointer.

If you are using bare LEDs they come with warnings not to look directly
at them (which are largely unnecessary since it is painful to do it).

Once the light is diffused it is just light like any other although the
colour rendering is a bit poor (though nowhere near as bad as CFLs).

And there are people who suffer the effects of any form of fluorescent
lamp such as getting skin and eye problems. Those with macular
degeneration are sometimes advised to wear yellow glasses outdoors to
reduce the impact of blue light (and, I assume, any UV).

Fluorescent lamps emit a fair amount of relatively short wave radiation
even in the conventional glass envelope. They also give a greenish cast
to photographs as the predominant mercury wavelength is in the green.

I understand that short wavelengths are not good for people with macular
degeneration.

Maybe, for some, LEDs are better than fluorescents and even quartz
lamps? (Or perhaps that should be "some LEDS"?)

"White" LEDs are essentially a shortwave blue LED emitter coated with a
yellow phosphor the exact composition of which determines the percieved
colour temperature. The mixture of blue and yellow light is a pretty
good approximation but its spectrum is different to natural sunlight.

This only really matters with a handful of materials that exhibit
serious depending on the character of ambient light.

http://en.wikipedia.org/wiki/Neodymium

Alexandrite is the canonical mineral and neodymium glass is the most
commonly seen example of this phenomena.

http://www.20thcenturyglass.com/glas...mium_glass.htm

http://www.gemstone.org/index.php?op...-gem&Itemid=14

--
Regards,
Martin Brown

In article ,
Martin Brown wrote:
Fluorescent lamps emit a fair amount of relatively short wave radiation
even in the conventional glass envelope. They also give a greenish cast
to photographs as the predominant mercury wavelength is in the green.

That entirely depends on the tubes. There is a big variety of colour
temperature and spectrums available from specialists. 'Standard' tubes may
be ok for lighting a corridor but can be greatly improved for domestic
use. The tubes will cost more - but with electronic control will have a
very long life.

--
*I didn't fight my way to the top of the food chain to be a vegetarian.

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

On 2014-09-12, Martin Brown wrote:

On 12/09/2014 08:49, Hugh Newbury wrote:

I seem to remember reading this somewhere. Can anyone tell me if it's
true or not?

If you stare at the actual bare illuminated LED die from point blank
range it's visible output is about equivalent to the surface brightness
of the sun. It doesn't have much thermal or UV component but it really
isn't good to look at. Same issue with staring into a laser pointer.

If you are using bare LEDs they come with warnings not to look directly
at them (which are largely unnecessary since it is painful to do it).

By "bare" you mean not even in the plastic blob that free-standing
LEDs usually have?

On 15/09/2014 11:43, Adam Funk wrote:
On 2014-09-12, Martin Brown wrote:

On 12/09/2014 08:49, Hugh Newbury wrote:

I seem to remember reading this somewhere. Can anyone tell me if it's
true or not?

If you stare at the actual bare illuminated LED die from point blank
range it's visible output is about equivalent to the surface brightness
of the sun. It doesn't have much thermal or UV component but it really
isn't good to look at. Same issue with staring into a laser pointer.

If you are using bare LEDs they come with warnings not to look directly
at them (which are largely unnecessary since it is painful to do it).

By "bare" you mean not even in the plastic blob that free-standing
LEDs usually have?

The water clear plastic blob lens doesn't much difference. It does make
the emitter occupy a slightly larger apparent angle but even so the
light intensity of the LED die is potentially damaging to the eye.

I meant without any diffuser or beam spreading optics in the way.

They have to be on a decent heat sink to run at high power.

--
Regards,
Martin Brown

Well, anything too bright or of a wavelength shorter than you can see can
damage the eyes. I've never heard of anyone having an issue as after all one
does not usually look at light sources directly normally.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Hugh Newbury" wrote in message
...
I seem to remember reading this somewhere. Can anyone tell me if it's true
or not?

Hugh

--

Hugh Newbury

www.evershot-weather.org

On 12/09/2014 11:36, Tim Streater wrote:
In article , Brian Gaff
wrote:

Well, anything too bright or of a wavelength shorter than you can see
can damage the eyes. I've never heard of anyone having an issue as
after all one does not usually look at light sources directly normally.

Even with filters an LED light will be too bright. Is why we ended up
not putting the in the bathroom, where you're gonna be lying down
looking up at them, potentially.

You could, at least in theory, have fitted LED uplighters and completely
avoided the possibility of seeing LEDs directly from your luxuriating,
soaped position. The issue is surely at least close to as bad with
quartz downlighters? It isn't the fundamental light source so much as
the lack of diffusion/dispersion to ensure that there is no extremely
bright spot that can be viewed directly.

--
Rod

On 12/09/2014 11:36, Tim Streater wrote:
In article , Brian Gaff
wrote:

Well, anything too bright or of a wavelength shorter than you can see
can damage the eyes. I've never heard of anyone having an issue as
after all one does not usually look at light sources directly normally.

Even with filters an LED light will be too bright. Is why we ended up
not putting the in the bathroom, where you're gonna be lying down
looking up at them, potentially.

Once they are inside a diffuser they are no different to incandescents.

You have got used to the claimed wattage equivalents of poxy CFLs but
the new generation of LED really are as bright as the incandescent that
they claim to replace and light up instantly. I got caught out by a
bathroom too - I got one for my parents because I worried about them
stumbling around in the half darkness as the CFL took an age to warm up.

The first LED unit I chose a nominally 60W equivalent was too bright!

--
Regards,
Martin Brown

On 12/09/2014 13:00, Tim Streater wrote:
We haven't been caught out in the bathroom as what we put in is a
fluorescent, not a CFL, and it has no discernible delay before coming
on.

So not the link you put in your response to me which says, quite
clearly, "CFL"?

--
Rod

On 12/09/2014 14:39, Tim Streater wrote:
In article , polygonum
wrote:

On 12/09/2014 13:00, Tim Streater wrote:
We haven't been caught out in the bathroom as what we put in is a
fluorescent, not a CFL, and it has no discernible delay before coming
on.

So not the link you put in your response to me which says, quite
clearly, "CFL"?

How witty. Not that I care one way or the other - the line between a
traditional fluorescent and what people think of when "CFL" is
mentioned, depends who you ask. Both are fluorescent, but whatever
Martin installed that apparently "caught him out" was evidently what
most people think of as a CFL - something that you plug into a 60W
lightbulb socket.

Err. No! You have precisely the wrong end of the stick.

It was a modern LED nominal 60W brightness device that was *VERY* much
brighter than the crappy nominal 60W slow to light up CFL it replaced.
CFL nominal 60W incandescent equivalent is more like 45W and I have yet
to see a convincing 150W incandescent equivalent in either CFL or LED.

What I linked to, we already knew would work fine as we already had one
installed elsewhere in the house. As I said, comes on straight away and
pretty much at full brightness.

LED units come on immediately at full brightness. No ifs no buts.

The price is getting competitive now too for replacements.

--
Regards,
Martin Brown

On Fri, 12 Sep 2014 20:14:23 +0100, Martin Brown
wrote:

On 12/09/2014 14:39, Tim Streater wrote:
In article , polygonum
wrote:

On 12/09/2014 13:00, Tim Streater wrote:
We haven't been caught out in the bathroom as what we put in is a
fluorescent, not a CFL, and it has no discernible delay before coming
on.

So not the link you put in your response to me which says, quite
clearly, "CFL"?

How witty. Not that I care one way or the other - the line between a
traditional fluorescent and what people think of when "CFL" is
mentioned, depends who you ask. Both are fluorescent, but whatever
Martin installed that apparently "caught him out" was evidently what
most people think of as a CFL - something that you plug into a 60W
lightbulb socket.

Err. No! You have precisely the wrong end of the stick.

It was a modern LED nominal 60W brightness device that was *VERY* much
brighter than the crappy nominal 60W slow to light up CFL it replaced.
CFL nominal 60W incandescent equivalent is more like 45W and I have yet
to see a convincing 150W incandescent equivalent in either CFL or LED.

What I linked to, we already knew would work fine as we already had one
installed elsewhere in the house. As I said, comes on straight away and
pretty much at full brightness.

LED units come on immediately at full brightness. No ifs no buts.

The price is getting competitive now too for replacements.

There is a chain of shops around Manchester that do LED wide-beam 5W
GU10s at £2.99. Choice of "cool" "daylight" or "warm". I thought the
price was good, but I'd be interested in hearing of any better deals
around.


--

Graham.

%Profound_observation%

On Fri, 12 Sep 2014 22:02:21 +0100, Tim Streater
wrote:

In article , Martin Brown
wrote:

On 12/09/2014 14:39, Tim Streater wrote:
In article , polygonum
wrote:

On 12/09/2014 13:00, Tim Streater wrote:
We haven't been caught out in the bathroom as what we put in is a
fluorescent, not a CFL, and it has no discernible delay before coming
on.

So not the link you put in your response to me which says, quite
clearly, "CFL"?

How witty. Not that I care one way or the other - the line between a
traditional fluorescent and what people think of when "CFL" is
mentioned, depends who you ask. Both are fluorescent, but whatever
Martin installed that apparently "caught him out" was evidently what
most people think of as a CFL - something that you plug into a 60W
lightbulb socket.

Err. No! You have precisely the wrong end of the stick.

It was a modern LED nominal 60W brightness device that was *VERY* much
brighter than the crappy nominal 60W slow to light up CFL it replaced.
CFL nominal 60W incandescent equivalent is more like 45W and I have yet
to see a convincing 150W incandescent equivalent in either CFL or LED.

What I linked to, we already knew would work fine as we already had one
installed elsewhere in the house. As I said, comes on straight away and
pretty much at full brightness.

LED units come on immediately at full brightness. No ifs no buts.

Yes, and we have a bunch of GU10 versions in the kitchen. We thought
also of using them in the bathroom (which was being renovated) but
decided against because even with diffusers, they have enough point
brightness to be irritating to older eyes. Hence why we installed the
fluorescent jobbie that we did. It has a built-in electronic ballast
which, AFAIK, is what is needed in such devices for immediate turnon.

In fact these "always-on" lights that cars seem to have now are going
to be very irritating as they are seem very often to be a string of
white LEDs and are very bright point sources.
I find the strobing of LED vehicle lights quite irritating.
It seems that some people don't notice it.

--

Graham.

%Profound_observation%

On 12/09/2014 08:49, Hugh Newbury wrote:
I seem to remember reading this somewhere. Can anyone tell me if it's
true or not?

Hugh


The study that was doing the rounds a while back was by Dr. Cecilia
Sanchez Ramos, but there have been others.

ISTM to be at the stage where there might potentially be an issue that
needs further investigation, at least with lights that emit excessive
blue, but that vested interests think there isn't.

In article ,
Hugh Newbury writes:
I seem to remember reading this somewhere. Can anyone tell me if it's
true or not?

This is a question which the EU is researching.

There is a health issue with exposure to intense blue light, which is
well known to laser operators (BLB - blue light blindness). Cumulative
exposure significantly increases chance of macular degeneration, but
above a certain threshold, it causes pretty instant blindess, although
there's a 24 hour delay following exposure before that happens and if
you know you've been exposed, there is an antidote which can be used
in that 24 hour window. (The exposure releases a chemical in the eye,
which in turn causes blindness, but that chemical can be mopped up if
caught in time.)

LEDs have a higher far blue component than filament lamps, and the danger
of macular degeneration and BLB is being considered. At the moment,
the EU believes it's not yet a problem for the public, but it is now
something which people with a larger exposure should protect themselves
against (such as someone regularly installing or relamping LED lamps).

Most white LEDs are actually blue LEDs with a phosphor to generate the
longer wavelength colours. In some high power industrial LEDs, the
phosphor is separated from the blue LED so that the LED chip does not
also have to dissipate the heat given off by the phosphor (the Stokes
Shift energy released when a high energy blue photon is changed into
a lower energy photon such as red). If such a lamp breaks or is
disassembled, then the high energy blue LED could be directly visible,
and carries the risk of BLB when handled at arm's length.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]