CFL Color Temperature

[Victor Roberts]

Over this past weekend I purchased a few screw-base CFLs.
I was greatly disappointed to find out that it was hard or
impossible to determine the color temperature of the CFLs
that I was trying to purchase. And, I'm supposed to be an
expert in this field!

None of the CFLs had a clear statement of the color
temperature on the package. Some of CFLs had numbers such
as 3000K or 5000K in small type buried among the other
numbers on the ballast compartment. We all know that these
refer to the color temperature, but what would these numbers
mean to the typical consumer if they are not identified?

Other CFLs had no indication whatsoever about the color
temperature. And still other CFLs used terminology to
describe the color that was taken from another context and
therefore was meaningless for this use. For example, GE
developed the term Soft White to describe the high diffusive
coating on incandescent lamps. It originally had nothing to
do with color temperature. Now GE is using Soft White to
describe the color temperature of their CFLs and certain
consumer fluorescent lamps. While I was at the store I had
no idea what CCT was associated with the Soft White. After
returning home I determined that GE Soft White CFLs have a
CCT of 2700K, but there are also many other GE CFLs that
have a CCT of 2700K that are not listed as Soft White.

While I understand that some people prefer a CCTs of4000K,
5000K, or even 6500K and respect those decisions, I also
believe that first time users of CFLs may be discouraged
from ever tying one again if they go to the store to by a
replacement for a normal incandescent lamp in their home and
return unknowingly with a 5000K CFL. Half of the bad press
for CFLs comes from what some people consider the "harsh"
light generated high CCT linear fluorescent lamps used in
offices.

I'm rather surprised and disappointed that Energy Star does
not require color temperature to be predominately displayed
on the box along with light output in Lumens and input power
in Watts. I'm going to encourage Energy Star to add the CCT
requirement to CFL packaging.

--
Vic Roberts
http://www.RobertsResearchInc.com
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site without written permission.

 

[Rusty]

While I understand that some people prefer a CCTs of4000K,
5000K, or even 6500K and respect those decisions, I also
believe that first time users of CFLs may be discouraged
from ever tying one again if they go to the store to by a
replacement for a normal incandescent lamp in their home and
return unknowingly with a 5000K CFL. Half of the bad press
for CFLs comes from what some people consider the "harsh"
light generated high CCT linear fluorescent lamps used in
offices.

I was talking to a electrician the other day after he had installed
fluorescent to replace a incandescent fixture in the break room. We got
to discussing CFLs, he mentioned he bought some for his house, but he
said that he didn't like how half his house has a 'bluish look' to it.

Granted, he probably didn't specialize in lighting, he just installed
the fixture and put whatever lights were on hand.


You would think the companies would realize this and market 2700K CFLs
as direct replacements for incandescents on the packaging.

 

[Victor Roberts]

I was talking to a electrician the other day after he had installed
fluorescent to replace a incandescent fixture in the break room. We got
to discussing CFLs, he mentioned he bought some for his house, but he
said that he didn't like how half his house has a 'bluish look' to it.

Granted, he probably didn't specialize in lighting, he just installed
the fixture and put whatever lights were on hand.


You would think the companies would realize this and market 2700K CFLs
as direct replacements for incandescents on the packaging.

I also believe that 2700K is the most appropriate CCT for
home use. Most of the CFLs that were marked at his store
were 3000K or higher. The only CFLs that were marked as
2700K CCT were a case of 12 Osram Sylvania.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
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This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

 

[[email protected]]

Over this past weekend I purchased a few screw-base CFLs. I was
greatly disappointed to find out that it was hard or impossible
to determine the color temperature of the CFLs that I was trying
to purchase.

Last summer, I wrote (in another group):

I was at Home Depot the other day and it was indeed marked on most of
the CFLs they sold. It wasn't on the front in the little "lumens/
watts/hours" box (where I think it should go), but it _was_ printed on
the back. The "nvision" brand had three different color temperatures
available and the packages were printed in different colors on a white
background. IIRC red was "soft white" and about 2800 K; green was
"bright white" and about 3500 K, and blue was "sunlight" or "daylight"
and about 5500 K.

More recently, one of the local Home Depots put up a small display on an
end cap near the CFLs. At first it was one of those three-lamp strip
fixtures (often used over a bathroom mirror with globe lamps) with three
CFLs in it, each with a different color temperature. The retail package
for each CFL was displayed in front of the lamp, so you could correlate
it with what was on the shelves. It was really easy to see the
differences in color, but the unshaded lamps also ended up being just
about at eye level and therefore rather glaring. They changed it to
three small portable fixtures ("desk lamps") with shades, again with the
retail package for the CFL displayed in front of each fixture. The three
fixtures were not all the same style, which doesn't really matter, but I
thought it wasn't as clear as the initial display; people might think
the color differences were due to the shades or some other property of
the fixture, rather than the lamps themselves.

Matt Roberds

 

[Andrew Gabriel]

In the UK, it's very difficult to buy anything other than 2700K
CFL's in standard retail outlets. Some of IKEA's are very slightly
higher CCT, I guess 3000K, but not marked as such.

Conversely, it's quite hard to find 2700K linear fluorescent tubes
in standard retail outlets. The default is 3500K.

 

[[email protected]]

| Over this past weekend I purchased a few screw-base CFLs.
| I was greatly disappointed to find out that it was hard or
| impossible to determine the color temperature of the CFLs
| that I was trying to purchase. And, I'm supposed to be an
| expert in this field!

As an engineer should should already know it's marketing issue.
They don't want to print all the specs on the box because it
confuses people (like those in the marketing department).


| None of the CFLs had a clear statement of the color
| temperature on the package. Some of CFLs had numbers such
| as 3000K or 5000K in small type buried among the other
| numbers on the ballast compartment. We all know that these
| refer to the color temperature, but what would these numbers
| mean to the typical consumer if they are not identified?

If the consumer does not know what color temperature is, which
describes nearly all of them, then it will mean nothing to them.
For all they know, it could be certification of Kosher compliance.


| While I understand that some people prefer a CCTs of4000K,
| 5000K, or even 6500K and respect those decisions, I also
| believe that first time users of CFLs may be discouraged
| from ever tying one again if they go to the store to by a
| replacement for a normal incandescent lamp in their home and
| return unknowingly with a 5000K CFL. Half of the bad press
| for CFLs comes from what some people consider the "harsh"
| light generated high CCT linear fluorescent lamps used in
| offices.

I'd prefer something around 2700K. I know I can get near that
with an incandescent bulb, and get a reasonably continuous
spectrum (at least no large gaps) as well. I only need that
for long term task lighthing (e.g. kitchen, shop, work bench).
All the rest can be [C]FL.


| I'm rather surprised and disappointed that Energy Star does
| not require color temperature to be predominately displayed
| on the box along with light output in Lumens and input power
| in Watts. I'm going to encourage Energy Star to add the CCT
| requirement to CFL packaging.

At least for "white" lights. I have not yet seen color bulbs in
CFL form, but it should not be hard to make them. I'm sure they
eventually will.

Many smaller lights can now be LED. Please include those in your
request for labeling requirements. I don't want some harsh blue
nightlight.

 

[Paul M. Eldridge]

Over this past weekend I purchased a few screw-base CFLs.
I was greatly disappointed to find out that it was hard or
impossible to determine the color temperature of the CFLs
that I was trying to purchase....

Hi Victor,

Even when I'm sure I know what I'm getting I often prove myself wrong.
For example, Osram Sylvania's "Daylight Plus" CFLs have a colour
temperature of 3,500K and with a name like that I would fully expect
these lamps to be 5,000K, or perhaps higher given the "Plus"
designation. What marketing genius thought this up?

BTW, I've grown to dislike 2,700K CFLs and find the aforementioned
Sylvania a good choice for residential applications. The only 2,700K
CFL I like, and it happens to be my all time favorite, is GE's 2D.
For the life of me, I can't explain why I like this lamp so much more
than anything else, but there's something very pleasing about the
light it produces. Is there any rational explanation for this or do I
need to cut back on my happy pills?

Cheers,
Paul

 

[Andrew Gabriel]

BTW, I've grown to dislike 2,700K CFLs and find the aforementioned
Sylvania a good choice for residential applications. The only 2,700K
CFL I like, and it happens to be my all time favorite, is GE's 2D.
For the life of me, I can't explain why I like this lamp so much more
than anything else, but there's something very pleasing about the
light it produces. Is there any rational explanation for this or do I
need to cut back on my happy pills?

I've used the GE 2D lamps in some fittings I've designed.
Their initial light output to final light output ratio is
not as bad as most other compact fluorescents. I use 2700K
and 3500K in different situations.

 

[Victor Roberts]

| Over this past weekend I purchased a few screw-base CFLs.
| I was greatly disappointed to find out that it was hard or
| impossible to determine the color temperature of the CFLs
| that I was trying to purchase. And, I'm supposed to be an
| expert in this field!

As an engineer should should already know it's marketing issue.
They don't want to print all the specs on the box because it
confuses people (like those in the marketing department).

Some of my best friends were marketing people

| None of the CFLs had a clear statement of the color
| temperature on the package. Some of CFLs had numbers such
| as 3000K or 5000K in small type buried among the other
| numbers on the ballast compartment. We all know that these
| refer to the color temperature, but what would these numbers
| mean to the typical consumer if they are not identified?

If the consumer does not know what color temperature is, which
describes nearly all of them, then it will mean nothing to them.
For all they know, it could be certification of Kosher compliance.

Then we need to explain what color temperature is. I've
seen a nice chart that does that.

| While I understand that some people prefer a CCTs of4000K,
| 5000K, or even 6500K and respect those decisions, I also
| believe that first time users of CFLs may be discouraged
| from ever tying one again if they go to the store to by a
| replacement for a normal incandescent lamp in their home and
| return unknowingly with a 5000K CFL. Half of the bad press
| for CFLs comes from what some people consider the "harsh"
| light generated high CCT linear fluorescent lamps used in
| offices.

I'd prefer something around 2700K. I know I can get near that
with an incandescent bulb, and get a reasonably continuous
spectrum (at least no large gaps) as well. I only need that
for long term task lighthing (e.g. kitchen, shop, work bench).
All the rest can be [C]FL.


| I'm rather surprised and disappointed that Energy Star does
| not require color temperature to be predominately displayed
| on the box along with light output in Lumens and input power
| in Watts. I'm going to encourage Energy Star to add the CCT
| requirement to CFL packaging.

At least for "white" lights. I have not yet seen color bulbs in
CFL form, but it should not be hard to make them. I'm sure they
eventually will.

I'm not sure there is a big enough market for color CFLs.

Many smaller lights can now be LED. Please include those in your
request for labeling requirements. I don't want some harsh blue
nightlight.

Energy Star has a separate set of "certification"
requirements for LED-based luminaires and replacement lamps.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

 

[Victor Roberts]

Hi Victor,

Even when I'm sure I know what I'm getting I often prove myself wrong.
For example, Osram Sylvania's "Daylight Plus" CFLs have a colour
temperature of 3,500K and with a name like that I would fully expect
these lamps to be 5,000K, or perhaps higher given the "Plus"
designation. What marketing genius thought this up?

BTW, I've grown to dislike 2,700K CFLs and find the aforementioned
Sylvania a good choice for residential applications. The only 2,700K
CFL I like, and it happens to be my all time favorite, is GE's 2D.
For the life of me, I can't explain why I like this lamp so much more
than anything else, but there's something very pleasing about the
light it produces. Is there any rational explanation for this or do I
need to cut back on my happy pills?

Cheers,
Paul

Well, there is some physics driving the high CCT of CFLs. As
you know, in normal fluorescent lamps the mercury produces a
bit of blue and green light that is mixed with the slightly
yellow light from the phosphor to make white.

It turns out that the current density in most CFLs is so
high that they generate a lot of blue light. So much in
fact that many CFLs use only a two-component rare earth
phosphor mix instead of the normal three-component mix.
There is just too much blue to have any more coming from the
phosphor. (If the phosphor does have all three components,
then the blue component is reduced in small diameter lamps.)
The 2D is made in a rather large diameter tube, at least
measured by CFL standards. I believe it is T5 for most
wattages, while most lower power CFLs use T4 tubing or even
smaller. The larger diameter discharge in the 2D, along
with the length, reduces the current density, which in turn
reduces the amount of blue light produced by the discharge.
This allows a three-component rare earth phosphor to be used
which may lead to high quality light.


--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.

 

[Don Klipstein]

Well, there is some physics driving the high CCT of CFLs. As
you know, in normal fluorescent lamps the mercury produces a
bit of blue and green light that is mixed with the slightly
yellow light from the phosphor to make white.

It turns out that the current density in most CFLs is so
high that they generate a lot of blue light. So much in
fact that many CFLs use only a two-component rare earth
phosphor mix instead of the normal three-component mix.
There is just too much blue to have any more coming from the
phosphor. (If the phosphor does have all three components,
then the blue component is reduced in small diameter lamps.)

Somehow I see either 3 or 4 phosphor bands/features in the spectra of
CFLs and "triphosphor" T8 fluorescents, Philips "Ultralume", etc. Could
two of these spectral features be from the same phosphor?

What I notice, in order from longer wavelength to shorter:

1. The strong orange-red linelike extremely narrow band around 611 nm,
along with some very weak similarly narrow bands nearby from yellow to
deep red,

2. a small group of wider but still very narrow bands in the green, with
the dominant feature maybe typically around 542 nm,

3. a dimmer, moderately narrow band in the green-blue/blue-green
with its brightest part around 485-490 nm but extending into the
blue-green around 500 nm, and

4. a wider still blue band, that with CFLs I usually only see when
nominal CCT is at least 3500K, mainly from 440-475 or 440-480 nm or so.

- Don Klipstein ([email protected])

 

[Paul M. Eldridge]

Well, there is some physics driving the high CCT of CFLs. As
you know, in normal fluorescent lamps the mercury produces a
bit of blue and green light that is mixed with the slightly
yellow light from the phosphor to make white.

It turns out that the current density in most CFLs is so
high that they generate a lot of blue light. So much in
fact that many CFLs use only a two-component rare earth
phosphor mix instead of the normal three-component mix.
There is just too much blue to have any more coming from the
phosphor. (If the phosphor does have all three components,
then the blue component is reduced in small diameter lamps.)
The 2D is made in a rather large diameter tube, at least
measured by CFL standards. I believe it is T5 for most
wattages, while most lower power CFLs use T4 tubing or even
smaller. The larger diameter discharge in the 2D, along
with the length, reduces the current density, which in turn
reduces the amount of blue light produced by the discharge.
This allows a three-component rare earth phosphor to be used
which may lead to high quality light.

Thank you, Victor, for explaining this. I had long suspected the 2D's
unusual design might have something to do with this, but now I know
the full story. Again, to my untrained eye, the quality of the light
it produces is noticably better than anything else I've seen to date
and it's the only 2,700K lamp I find pleasing.

Best regards,
Paul

 

[Paul M. Eldridge]

I've used the GE 2D lamps in some fittings I've designed.
Their initial light output to final light output ratio is
not as bad as most other compact fluorescents. I use 2700K
and 3500K in different situations.

Hi Andrew,

I'm sure this lamp's unusual design and significantly larger size
makes fixture design a bit more challenging. Do you have links to any
of the work you've done with this particular lamp?

Cheers,
Paul

 

[TKM]

Thank you, Victor, for explaining this. I had long suspected the 2D's
unusual design might have something to do with this, but now I know
the full story. Again, to my untrained eye, the quality of the light
it produces is noticably better than anything else I've seen to date
and it's the only 2,700K lamp I find pleasing.

Best regards,
Paul

I've noticed the same thing and have long suspected that the width or
"fatness" of spectral lines - especially as found in fluorescent and HID
lamps -- has something to do with the color quality and acceptance of light
by users. That aspect of light and color is not well-captured in our current
color rendering and chromaticity metrics.

The same thing is likely to affect the perception of color quality for LEDs
and I've discussed the idea with the group that's looking at new color
measurement standards for LEDs. Plus the notion came up in the LRO Light
and Color Symposium in 2006, so there's now a bit of research on it.

The 2D lamp design got a lot of things right and, unfortunately, the full
range of features was never well undertood or promoted although I give GE
credit for keeping the lamp, as designed, in their product line. I
particularly liked the 55W version as used in the "Berkeley Lamp". It used
a desk lamp configuration and two lamps (one for uplight; the other for
downlight) with separate dimmers that still work better than any other CFL
dimmer that I've seen. See:
http://enews.lbl.gov/Science-Articles/Archive/cfl-tablelamp.html

Terry McGowan

 

[Paul M. Eldridge]

I've noticed the same thing and have long suspected that the width or
"fatness" of spectral lines - especially as found in fluorescent and HID
lamps -- has something to do with the color quality and acceptance of light
by users. That aspect of light and color is not well-captured in our current
color rendering and chromaticity metrics.

The same thing is likely to affect the perception of color quality for LEDs
and I've discussed the idea with the group that's looking at new color
measurement standards for LEDs. Plus the notion came up in the LRO Light
and Color Symposium in 2006, so there's now a bit of research on it.

The 2D lamp design got a lot of things right and, unfortunately, the full
range of features was never well undertood or promoted although I give GE
credit for keeping the lamp, as designed, in their product line. I
particularly liked the 55W version as used in the "Berkeley Lamp". It used
a desk lamp configuration and two lamps (one for uplight; the other for
downlight) with separate dimmers that still work better than any other CFL
dimmer that I've seen. See:
http://enews.lbl.gov/Science-Articles/Archive/cfl-tablelamp.html

Terry McGowan

Thanks, Terry. Comforting to know my mind isn't playing ticks on me.
Mine are 39-watt tri-'s and must be close to ten years in age. And to
echo Andrew's comments, no noticable drop in light output even after
several thousands of hours operation. The reusable electronic ballast
is a nice plus too.

Cheers,
Paul

 

[[email protected]]

I'm not sure there is a big enough market for color CFLs.

FWIW, I saw colored CFLs at Wal-Mart while shopping earlier this
evening. They were available in red, orange, yellow, green, blue,
and "black"/UV. These were all 13 W (60 W equivalent) spiral CFLs by
Feit Electric. The red, orange, green, and blue ones were marketed as
"party bulbs"; the yellow one was actually marked as an anti-insect
lamp. I took a close look at the red and orange ones, and I *think*
they used colored glass, as opposed to a coating on the outside of
clear glass. They sold for about $4 or $5 each.

Wal-Mart sells another brand of anti-insect CFL (GE or Philips - I
can't remember) that appears to have a translucent yellow plastic
covering over a normal CFL.

Matt Roberds

 

[Andrew Gabriel]

Hi Andrew,

I'm sure this lamp's unusual design and significantly larger size
makes fixture design a bit more challenging. Do you have links to any
of the work you've done with this particular lamp?

I must get round to putting up some pictures. The only one up
at the moment was the first one I converted...
http://www.cucumber.demon.co.uk/lights/diy2/
The ones I've done since then all use the 21W lamp.

The following might be amusing too, although it predates that:
http://www.cucumber.demon.co.uk/lights/diy/
The downlighters shown there are still in pretty continuous use
every day, for around 10 years now. Only one further capacitor
has had to be replaced since I wrote that article.

 

[Paul M. Eldridge]

I must get round to putting up some pictures. The only one up
at the moment was the first one I converted...
http://www.cucumber.demon.co.uk/lights/diy2/
The ones I've done since then all use the 21W lamp.

The following might be amusing too, although it predates that:
http://www.cucumber.demon.co.uk/lights/diy/
The downlighters shown there are still in pretty continuous use
every day, for around 10 years now. Only one further capacitor
has had to be replaced since I wrote that article.

Thanks, Andrew. Very cool. Please let us know when more pics are
available, as it's always interesting to see what others are doing.

Cheers,
Paul

 

[[email protected]]

On Fri, 15 Feb 2008 09:44:44 GMT [email protected] wrote:

|> On 12 Feb 2008 21:19:38 GMT, [email protected]
|> wrote:
|>
|>> I have not yet seen color bulbs in CFL form, but it should not be
|>> hard to make them. I'm sure they eventually will.
|>
|> I'm not sure there is a big enough market for color CFLs.
|
| FWIW, I saw colored CFLs at Wal-Mart while shopping earlier this
| evening. They were available in red, orange, yellow, green, blue,
| and "black"/UV. These were all 13 W (60 W equivalent) spiral CFLs by
| Feit Electric. The red, orange, green, and blue ones were marketed as
| "party bulbs"; the yellow one was actually marked as an anti-insect
| lamp. I took a close look at the red and orange ones, and I *think*
| they used colored glass, as opposed to a coating on the outside of
| clear glass. They sold for about $4 or $5 each.
|
| Wal-Mart sells another brand of anti-insect CFL (GE or Philips - I
| can't remember) that appears to have a translucent yellow plastic
| covering over a normal CFL.

They haven't figured out to use a different kind of fluorescing material?
Or maybe they have, but are cleaning the spectrum with the coloration of
the glass or outer coating.

 

[[email protected]]

19:38 GMT, [email protected]
|> wrote:
|>
|>> I have not yet seen color bulbs in CFL form, but it should not be
|>> hard to make them. I'm sure they eventually will.
|>
|> I'm not sure there is a big enough market for color CFLs.
|
| FWIW, I saw colored CFLs at Wal-Mart while shopping earlier this
| evening. They were available in red, orange, yellow, green, blue,
| and "black"/UV. These were all 13 W (60 W equivalent) spiral CFLs by
| Feit Electric. The red, orange, green, and blue ones were marketed as
| "party bulbs"; the yellow one was actually marked as an anti-insect
| lamp. I took a close look at the red and orange ones, and I *think*
| they used colored glass, as opposed to a coating on the outside of
| clear glass. They sold for about $4 or $5 each.
|
| Wal-Mart sells another brand of anti-insect CFL (GE or Philips - I
| can't remember) that appears to have a translucent yellow plastic
| covering over a normal CFL.

Now all I need are some colored HID lights. Maybe they would know to
use different HID technologies for the different colors. Unfortunately
there is probably no market for 400 watt HID colored bulbs. They could
be used on giant Christmas trees, though.