# Help Critique My CFL Bulb Guide.



## Ken_McE (Jul 15, 2006)

I'm writing up a guide to compact fluorescent bulbs for eBay. If it seems appropriate I thought I might add it to the CPF wiki too. I would be greatful for any helpful comments anyone might have for improving it:



*Introduction:*

Compact fluorescent bulbs (CFLs) are small fluorescent bulbs with a screw-in base. They combine the simplicity of incandescent bulbs with the efficiency of fluorescent lighting.

A CFL should last roughly eight to ten times as long as a comparable incandescent. If it is mounted in an air tight fixture or a hot location you should expect a shorter life for the bulb. Around 750 - 1,000 hours is a common burn time for an incandescent bulb and around 8,000 - 10,000 hours is normal for a CFL. A CFL will lose perhaps 20% of its brightness over the first 2,000 hours of burn time, so it it not a bad idea to get one that starts out brighter than you need.

An incandescent bulb will radiate about 90% of its energy as heat and 10% as light. A CFL will be closer to 75% heat and 25% light. This means a CFL should produce about three to four times as much light (lumens per watt) as a comparable incandescent. They will also produce less heat than a comparable incandescent bulb.

CFLs have a higher initial cost. An ordinary 100 watt incandescent bulb will produce 1,700 lumens of light and has an initial cost of around $.75 to $2.00 A comparable CFL would cost around $6.00 and use about 26 watts to produce the same 1,700 lumens.
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Color Temperature:*

Manufacturers use a system called "Color Temperature" to help describe the quality, the exact tone of white, that their bulbs emit. Incandescent bulbs have a temperature of around 2,800K, which is a yellowish white. A lower number , such as 2,400K would start to look reddish. A higher number, say 5,000 to 6,000K will have more of a bluish white color. By comparing numbers you can get a fair idea of what the light from your bulb will look like before you buy it.

The light from an incandescent bulb will be a warm yellowish color that people are accustomed to. The light from a CFL will often tend to be a much cooler blue-white. In public spaces people don't mind bluish light. In a private setting, or in a situation where you will need to see colors particularly well, you should try try using just one or two and make sure you like the look before you get a case of them. If a listing does not say what the color temperature is, you should assume that it is bluish-white. If a listing says "Warm White" then it will more like an incandescent and less blue.

*When Are CFLs Better?*

CFLs will normally cost more up front, but save you money over the life of the bulb because you will spend less on electricity, and spend less time changing bulbs. CFLs are better if you pay for the electricity, and for spots where it is hard to get at the bulb to change it.

Incandescent bulbs are essentially immune to extreme heat and cold. CFLs will have a shortened life in an enclosed fixture or other very hot situation. They may start slowly or be dim at first if they are in a very cold area. Some CFLs may get cranky below 32 degrees F. Incandescents are also better if you have a light that gets turned on and off quite frequently, as this tends to wear out CFLs. Incandescents may also be the logical choice if someone else pays for the electricity, if the bulb is liable to be stolen, or in a spot where bulbs often get broken .

CFLs can generate radio interference. They may cause interference with IR remotes and IRDA data transfer devices. Incandescents will not.

*Dimming:*

Almost any incandescent bulb can be dimmed without harming it. Most CFLs take badly to dimming. There are a few CFLs that are specifically made to work with dimmers. They will mention that right on the box. unless the listing specifically says so, you should assume the bulb cannot be dimmed. If you try to dim it anyhow, you will probably kill it.

*Size:*

CFLs are more efficient with electricity, but less efficient with space. They will tend to be both longer and wider than a comparable incandescent bulb. If you have a tight space you may want to check the size of the bulb before you get it.

*Manufacturers claims:*

You need to read CFL listings carefully. Different manufacturers aim towards different goals. One plant may be trying for the longest bulb life, another may be trying for a bulb that renders colors particularly well, another may be aiming for the lowest possible cost per unit. 

Their advertising will sometimes stretch the truth a bit. If you look at the numbers for brightness, measured in lumens, color temperature, measured in degrees K, and power consumption, measured in watts, you should be able to see through most exaggerations. They will always mention their particular strength prominently. If a particular number is missing from a product it is because they would prefer not to focus on a weakness.

CFLs are often a good choice, sensible and economical, once you get used to the small differences between the old incandescent and the new compact fluorescent technologies.


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## jtr1962 (Jul 16, 2006)

Ken_McE said:


> Incandescent bulbs have a temperature of around 3,500K, which is a yellowish white.


The only incandescent bulbs with a color temp of 3500K are very short life projector and flashlight bulbs. Typical household incandescents have color temps under 3000K, and usually lower wattage bulbs have lower color temps. A 200 watt bulb is around 2900K. A 60 watt bulb is about 2700K. Small base 40 watt candelabra bulbs are usually under 2500K. Also, "long life" bulbs tend to have lower color temperatures than equivalent wattage standard bulbs.



> The light from an incandescent bulb will be a warm yellowish color that people naturally like.


I would leave that part out. Color temp is a personal preference and just as many people prefer cooler light as warmer light. Even many of those who say they "prefer" warmer light may actually just be conditioned to it from years of using incandescents.



> The light from a CFL will tend to be a much cooler blue-white. In public spaces people don't mind bluish light.


This was certainly true when CFLs came out 20 years ago but most sold in retail stores these days tend to be warm white. It's actually a long-running pet peeve of mine that higher color temps aren't readily available except through mail order.



> In a private setting, or in a situation where you will need to see colors particularly well, you should try try using just one or two and make sure you like the look before you get a case of them.


You might mention that CRI is the best determinant of how well you can distinguish between colors which are close. This is quite different from seeing colors accurately. For example, an incandescent lamp has a CRI of 100 which makes distinguishing between close colors possible but because the color temp is way lower than sunlight the colors seen can hardly be described as accurate. Most CFLs have a CRI in the 80 to 84 range which is acceptable but not spectacular. Some are available with CRIs as high as 96, although usually in a color temp of 5000K to 5500K.

Other than those minor points, excellent write-up!


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## NewBie (Jul 16, 2006)

You might add that turning CFL lights off and on frequently, greatly shortens their life.

A number of CFL lights cause RF interference which can cause issues.

CFL lights, especially dimmable ones, can cause issues with IR remotes and IRDA data transfer devices.

Many CFL bulbs have difficulties when temperatures get down in the 32F and below range. Some CFL bulbs can deal with this, starting fine as low as 15F.


If you thought your CFL bulbs appear quickly dim, it isn't your eyes playing tricks on you.

While CFL bulbs have high efficiencies in the beginning, their light output drops down in the 80% range in as little as 4000 hours- even on a long life rated 10,000 hour bulb, with a rather quick drop in the first 2,000 hours.

http://www.gelighting.com/na/busine...ell_sheets/downloads/cfl/28306_42w_spiral.pdf

The situation is worse with typical consumer grade CFL lamps/bulbs.


That should be enough to get you started.


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## evan9162 (Jul 16, 2006)

One important thing to mention:

Heed the manufacturer's reccomendation as to usage in enclosed or recessed fixtures. Some mfgr's bulbs can be used pretty much anywhere (Commercial Electric bulbs from Home Depot are good about this), while others say don't used in enclosed or recessed fixtures. This is important, as using a CFL in an enclosed fixture when it's not designed for it can result in early bulb death. I placed a GE 23W CFL in a recessed fixture when the instructions warned specifically against that. It died after 2 weeks of use. However, I've had Commercial Electric bulbs in fully enclosed fixtures for 2 years now without any problems. So make sure the bulb can handle the application you have in mind or you will likely end up with a dead bulb.


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## Handlobraesing (Jul 16, 2006)

I've had my share of bad CFLs that lasted less than a regular light bulb and they are more and more common with el-cheapos these days. I wouldn't feel comfortable buying them in bulk unless you could back it up with a warranty.

These cheapos become some expensive light bulbs when they start popping after 500 hours.


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## TedTheLed (Jul 16, 2006)

I bought several Philips "Earthlight" cfl lamps because they were claimed to be dimmable, rfi free, and came inside weatherproof globes.

I wouldn't recommend anyone buy a cfl without those qualities -- brown-outs are a fact of life, and if the fluorescent isn't dimmable it can burn right out (literally; before the Philips, one of my non-dimming fixtures burned a hole in it's plastic base during a 'brownout' one summer in New York..)

I haven't bought a cfl in over ten years, so I don't even know if they still make them. I sure hope so. Can anyone clue me in?

btw I prefer a slight warmth (pink) to a cool blue, it just seems to make people look healthier.. and the weatherproof globe on the Philips earthlights makes the glow of cfls much more even and, nice..


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## NewBie (Jul 16, 2006)

Anything like this Ted?


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## TedTheLed (Jul 16, 2006)

yes, eggsackly! brownout?

(go dimmable.)


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## JimH (Jul 16, 2006)

Here's a good site to check out. I use 12v 2700k CFL's for camping.


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## TedTheLed (Jul 17, 2006)

yup, 19 and 93, that's when Philips first introduced the 'folded bridged' cfl in the US, the sls -- 

http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/94/940103.html


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## Melchior (Jul 17, 2006)

Also some CFL's have a shortened life when run in 'downbase' position. Some manufactuerers will warn about this, most don't.
(standard really for ceiling lights)

Also "Energy Star" marked CFLs have a rated colour temperature of 2700K, this is intentional as it is meant to replace 'soft-white' bulbs. Thats the default colour temperature more or less.

Be shure to tell about the CRI or Colour Rendering Index, where 100 is perfect for colour rendition and the average 2700 Kelvin CFL has a CRI of 82, which is less than perfect but acceptable for most use.


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## yuandrew (Jul 18, 2006)

I heard Philips might have been first to introduce the CFL in the form of a magnetically ballasted unit the size of a soup can back in the early 80's. Mitsubishi Electric later followed with their Marathon bulb but they were sued by Philips because of the similar product design and patent infringments. My uncle still has a pair of Mitsubishi Marathon 15 watt bulbs from 85' still going in two table lamps though. Ironically, Philips renamed their Earthlight line to Marathon just a few years ago.

The now common spiral flourescent lamp was first invented by GE in 1976 but the equipment for production wasn't made until 1992. The GE Helix CFL however never got to mass production (source-lamptech). It wasn't until late 1997 or 98 when Lights of America re-introduced the spiral CFL as "The Twister" series did spiral CFLS get popular and are now mass produced by many Asian manufacturers plus marketed cheaply.

Philips introduced their Earthlight Dimmable to market in 1996 I think but I think they discontinued makeing them since it is no longer listed on their site. I did find some early models with the Earthlight brand still on them at my Big-Lots for $4.00 each however. The only other companies I know of making dimming CFLS are Greenlite (a chinese company) and TCP. I did hear the TCP dimmables create interferance with remote controls and X10 when dimmed so you might want to take that into consideration if you have home automation devices. Philips and Greenlite works fine with X10 and my Philips seems ok with my TV remote.


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## Canuke (Aug 4, 2006)

Regarding color CFL's, here's a few tidbits.

The only color CFL's I've found in stores (around Los Angeles CA) are the Feit brand, and TCP. The main knock on Feit is that they use the same warm-white phoshors in color bulbs as they do regular ones, and then just filter them, the same as incandescents. This is OK for red, orange and yellow bulbs, but their green and blue ones are very dim, inefficient, and are very desaturated.

TCP, on the other hand, starts off with the nearest color phosphor and filters from there, resulting in a much brighter, richer color for their blue and green. I have their blue, its color is comparable to the output of 470nm blue LED's. Their soft pink is all phosphor, no filtering at all, and is consequently really bright.


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## MoonRise (Aug 8, 2006)

Color temperature, also called CCT for "Correlated Color Temperature", is measured in degrees Kelvin and relates to the color of the light produced. Or more correctly, it relates to the temperature an object, like a filament or black-body radiator, would have to be to radiate light of a similar color. Think of a coil of an electric stove or a piece of metal being heated very hot. As it gets hotter, the color changes from a dull red to a brighter red, and then to even brighter colors as it gets hotter and hotter. At a temperature of around 2700 K, the color would be similar to the light produced from common 40-60 Watt incandescant light bulbs. As the temperature or CCT rises, the color changes from reddish, to orangish, to yellowish, to whitish, to bluish. Within limits, your eyes and brain will adjust to various CCT light sources and try to make 'white' things white. Different CCT light sources are also why digital imagers (cameras and video cameras) usually have a setting to adjust the "white balance", because your brain can be partially fooled or can compensate for different CCT light sources but the camera has to be adjusted (manually or automatically) for different CCT light sources.

Having different CCT sources in view at the same time is generally a simple and easy way to see the difference between them, because then the eyes and brain can't really make both sources 'white' at the same time so you can better see the differences between them. Look at an incandescent bulb and a fluorescent bulb by a sun-lit window and you can pretty quickly see the CCT differences between the three light sources.

Color Rendering Index, or CRI, is a scale used to describe the quality of the light and how well colors can be seen. The scale is from 0 to 100, and midday summer sunlight is the basis for a CRI of 100. Incandescent bulbs almost always have a CRI of 100, but because fluorescent bulbs (and other lighting technologies like the various vapor lamps, such as mercury, sodium, etc) work differently, they can have CRI values ranging from 20 to 96 or so. The higher the CRI, the better and more realistic colors can be seen.

Your (Ken_McE) statements in your original "Color Temperature" block are sort of close but not really correct, especially in a reference document. IMHO you should rewrite it.

Also, some of your statements saying "any" or "all" should probably be changed to "many" or "most". If you write a statement as an absolute (any, all, never, none, always, etc), then a single counter-example makes your statement false. Such as "Any incandescent bulb can be dimmed without harming it." Well, not quite. One counter-example is if you take a quartz-halogen bulb and dim it to a certain point then it will rapidly blacken and fail.

Regarding interference, I think it would be more correct to state:

CFLs can generate radio interference or RFI (Radio Frequency Interference). They may cause interference with electronic devices.

RFI would not affect just IR or IRDA devices.

Also, regarding lumens. Lumens is a measurement of how MUCH light a device produces, not it's brightness. More lumens landing on a viewed area makes it brighter, but not because the lumens themselves are brighter. Brightness is actually measured in candlepower. A common laser pointer is very bright (damaging to the eyes bright), but the lumen output is very low. A common 4 foot long fluorescent bulb is really not all that bright, but it usually produces more than 2000 lumens. So the fluorescent bulb is used to light up a room (lots of distributed lumens) but a simple laser pointer is brighter and can still be easily seen in the well lit room. If you take a certain amount of lumens and through lenses, optics, and/or reflectors -concentrate- those lumens on a smaller and smaller area, than that area will be brighter and brighter. Even though the lumens is the same.


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## Norm (Aug 8, 2006)

Ken_McE said:


> A CFL will be closer to 75% heat and 25% light.


Seems you have reversed the figures here.


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## Lightmeup (Aug 9, 2006)

Norm, I think he is right.


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## benighted (Aug 9, 2006)

Where can you get the high color temp CFL's? It seems like any of the newer CFL's you can get are less than 3000k :candle:


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## yuandrew (Aug 11, 2006)

You have to look around for them; Home Depot used to sell some by Philips that said "Daylight 50" on them, Lowes has some Sylvania Daylight Extra lamps that are around 4000K, and Wal*Mart has the Lights Of America Fluorex 6500K bulbs.

Other than those, you'll probably have to order them. Search for "full spectrum" CFL bulbs or look for anything with a color temp of 4100K-6500K.


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## Norm (Aug 11, 2006)

Norm said:


> Seems you have reversed the figures here.





Lightmeup said:


> Norm, I think he is right.



From here http://www.cityofdavis.org/yeep/cfl.cfm

*Less Heat* Because twisters use 90% of the energy to produce light, very little heat is generated, which reduces cooling costs.


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## brickbat (Aug 11, 2006)

Ken_McE said:


> ...A CFL will be closer to 75% heat and 25% light.



This is definitely not reversed.


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## brickbat (Aug 11, 2006)

Norm said:


> ...Because twisters use 90% of the energy to produce light....



Very deceptive. I suspect the cover their butts by taking the position that the electronic ballast within the CFL is 90% efficient.

That, or they are simply liars.


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## Ken_McE (Aug 13, 2006)

*Re: Help Critique/Efficiency*

Guys, fluorescents are much more efficient than incandescents, but they are not perfect, at least not yet. Just put your hand on the base of a CFL after its been running a while. They get hot. Also, I am not aware of any technology that is 90% efficient at converting energy to light. (bioluminescense maybe??) 

What do the numbers say?

Let's start off with an incandescent bulb. I consider a 100 watt Incan. producing 1,700 lumens to be a good benchmark:

http://www.bulbs.com/products/product_detail.asp?page=products&inventory=8543

It will produce 17 lumens per watt, running at 10% efficiency, which is typical for incandescent bulbs. At 100% efficiency, it would go up to 170 lumens per watt. At 90% efficiency that would be around 150 lumens per watt.

Let's take the second CFL on the next link. It uses 26 watts and produces 1,750 Lumens. At 1/4 of the energy for essentially the same light, it is a quite reasonable for a 100 watt replacement CFL:

http://www.wattbusters.com/store/home.php?cat=268

1,700 lumens (I expect it to dim after burn in) divided by 26 watts gives us 65 lumens per watt. This is about four times the efficiency of the 100 watt incan. above, but well below the 90% efficiency claim in the Yeep posting. I would say their hearts are in the right place, but that their numbers are off. They may not be looking at the entire bulb to generate that figure.

benighted,

Lately I have been using very large (thirteen inch), very high output CFLs. They are not really consumer models. Most of the ones I find are in the 6~6,500 K range. There are some that are lower temp, particularly in the red range, I believe they are intended for grow rooms. I am sorry that I cannot give you a specific reference for high K bulbs.

Moonrise,

I have been struggling with how to leave out the whole business of color temperature from the article, even though I'm not sure if this is possible. My concern is that it is just too technical for some eBayers. I want an article that is very, very simple and easy to understand. The target audience is people who just wanna use one a them twisty bulbs and save some money even if they don't know a lot about light, electricity, or electronics. I'm hoping to help them spend their money well and not buy a fancy $10 bulb without getting their moneys worth.

That said, your comments are spot on. Would you consider donating your comments to the CPF Wiki? Your writing would make a solid foundation for a "Color Temperature" article.


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## jtr1962 (Aug 13, 2006)

*Re: Help Critique/Efficiency*



Ken_McE said:


> I have been struggling with how to leave out the whole business of color temperature from the article, even though I'm not sure if this is possible. My concern is that it is just too technical for some eBayers. I want an article that is very, very simple and easy to understand. The target audience is people who just wanna use one a them twisty bulbs and save some money even if they don't know a lot about light, electricity, or electronics. I'm hoping to help them spend their money well and not buy a fancy $10 bulb without getting their moneys worth.


Color temperature isn't a hard concept to grasp for the average person. Basically, it's how yellow or white or blue a light source is. Anyone can relate to that. It's just that most people either don't notice or don't care. However, these same people will feel like they didn't get their money's worth if they don't like the color of the bulb they bought. I think color temperature belongs in any discussion of CFLs. In fact, one of the beauties of CFLs is that they not only allow you to replace your incandescents with something more efficient, but you're no longer limited to the 2700K to 2900K color temperature of incandescent (which quite a few people dislike intensely).


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## Lightbender (Aug 30, 2008)

Color Temp. : these days, you can get cfls in a variety of color temperatures. Even cooler, I actually just started using some colored cfls at work, and the colors are(in my opinion) more vivid than the 25w coated incandescent equivalent. 

I certainly agree with the previous comments in regards to color temperature and personal preference. I'm a big fan of the 'reveal' lamps, and have yet to find a comparable replacement in cfl form.


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