Getting More From Fluorescent  and Other Lamps 

Color accuracy also discussed.

Standard Fluorescent Lamps are about three to four times as efficient as incandescent lamps.

I've had problems with short lamp life with a few low-wattage desk lamp fixtures. It's hard to avoid poorly made fixtures. They often come with inadequate ballasts, a transformer-like device in all standard fluorescent fixtures. The ballast limits the current in the lamp. A ballast that is cheaply made allows too much current in the lamp, which makes it very bright at first. Then the ends blacken rapidly and in perhaps 1,000 hours, the life of a regular light bulb, they won't start. Normally fluorescent lamps should burn for at least 5,000 hours. What I have found is that it helps to lower the voltage to these fixtures in a safe manner with an external high-wattage resistance. This would require knowledge of making safe, customized electrical installations.

You may want to discard or recycle these old fixtures. Very old ballasts may contain PCBs (polychlorinated biphenyls, a persistent environmental poison.) Many localities now have hazardous material recycling events, and old fluorescent lamps also qualify because they contain mercury.

If you have the option, purchase standard fluorescent fixtures with a high efficiency ballast. It will save power and the lamps will last longer. Standard lamps are generally available in the daylight, cool white, and warm white colors. Cool white is by far the most common color in homes. It is sometimes possible to use 25 watt lamps in 40 watt fixtures but they will have a shorter life.

Standard fluorescent fixtures most commonly use 40 watt lamps in series-connected pairs, driven by a rapid-start ballast. These fixtures have no old-fashioned starters. The lamps must be of equal wattage. It is preferable to use new lamps in each pair when replacing them. You can squeeze a little more life out of some used lamps in these fixtures by testing them with a known good lamp as the other pair member. Then these used lamps can be installed as pairs for a few weeks or months more life.

Older fixtures have neon-based starters, which are in twist-to-lock sockets. These must be replaced if good lamps fail to start, or the lamps glow at the ends steadily. In these fixtures, allowing old lamps to blink for very long causes the starters and possibly the ballast to fail. Lamps are individually connected to the power with a ballast for each.

Never use incandescent lamp dimming devices with standard fluorescents.

Compact Fluorescent Lamps (CFLs)

This type of lamp has become more common in the 15 years or so it has been around. They are very worthwhile to use because they can last up to 10 times as long as a standard incandescent. They have become similar in price to incandescents recently. And they use about 1/3 to 1/4 the power. They use a solid-state (transistorized) ballast to limit lamp current.

Usually the color temperature is specified on the package. 2800 or 2900 K is the color of a standard light bulb. Colors over 4500 K are more like daylight. There are some lamps that claim to have a more accurate color or "full spectrum." These are somewhat more accurate in color than the "full-spectrum" incandescent lamps described below, but still less accurate than natural daylight or "color corrected" bluish incandescent lamps.

There are a few conditions where the CFL will not work out well. Solid state ballasts cannot tolerate heat or voltage spikes. So CFLs should not be placed in recessed enclosed fixtures with a glass cover, to avoid heat buildup. And CFLs should not be placed in a switched circuit with a fan or standard fluorescent lamp. When the circuit is switched off, the fan or standard lamp ballast will send a voltage spike to the CFL that will short out its ballast. The CFL will then burn out rapidly when the circuit is turned back on.

Another limitation is the physical size of the glass and the base. To fit the glass area, you may need to get a larger lamp "harp", the metal part that holds the shade. Or you may be able to fit a lower wattage CFL in. Since the base contains an electronic ballast, it is larger than the base of a comparable standard incandescent lamp. You can overcome this problem by using an extender socket found in hardware stores. I have not yet found extender sockets for 3-way CFLs.

CFLs are designed to give a lot of light from a small glass area, but for maximum lamp life, burn two- and three-way lamps at the lower settings.   It is normal for them to need up to 5 minutes to reach full brightness. This is necessary to keep them from being overdriven when fully warmed up. Three-way lamp sockets for incandescent lamps are compatible with 3-way CFLs.

You may use an incandescent lamp dimmer ONLY with CFLs marked "dimmable." These will not dim as completely as incandescent lamps. Below a certain setting, they will flicker or go out.   Regular CFLs will flicker visibly all the time with incandescent dimmers or photoelectric switches and the ballast will soon be destroyed. Some photoelectric switches or timers may be compatible with ordinary CFLs. They will be so marked on the package.

The ballast in CFLs normally causes them to flicker invisibly at a very fast rate. This might be something like 50,000 times per second. This can cause them to interfere with infrared remote controls that are common for your stereo or television devices. You may need to use standard incandescent light bulbs or standard fluorescent lamps near these appliances if CFLs cause the remote control to "lock up."

Consumer Reports has comments on CFLs in the May 2008 issue, and in the October 2009 issue.

Incandescent Light Bulbs

The old standby wastes power and should not be used where a CFL will work. They may be good for high wattage types that give some heat, as in your bathroom. Incandescent lamps are inefficient because most of their energy is radiated in the infrared spectrum that we cannot see. They are still good for where you don't need much light, in the 4 and 7 watt sizes. Of course, they come in many special decorative types. You'll notice that the ones over 7 watts with the small (candelabra) bases and flame shapes are burned base down. This is to avoid overheating and separating the base from the glass, which makes them hazardous to remove. Now there are 1/2 watt LED lamps to replace the 4 to 7 watt lamps, and LED lamps of about 9 watts that can replace 40-watt flame-shaped incandescent lamps.

In the next few years, I have heard, standard incandescent lamps of 40 thru 100 watts will no longer be available, by law, to save energy and the environment. Electrical generation is a leading source of CO2. I think that special shapes, such as flame, and special bases, such as candelabra, will continue to be available. CFLs in these shapes and base types are very large and don't fit well in some fixtures. The flame-shaped CFLs are getting smaller all the time, though. The new LED types above, are smaller.

Long-life incandescent bulbs and "Full-Spectrum" bulbs are often found in catalogs. Long-life types sound like a great bargain, but the tradeoff is reduced light output per watt, making them even less efficient. This is marked enough to cause you to use about one size larger lamp. The filament is longer and burns at a lower, yellower temperature. This is the same as buying a higher voltage lamp, such as 130 volts, and operating it at the standard 120 volts. This is fine for things like hard-to-access exit signs. Sometimes even 240 volt lamps are installed in exit signs. They will burn for about 10 years. However, they are quite dim.

"Full-Spectrum"  incandescent bulbs claim to have a more natural color or to pep up some colors. These lamps have a light purple to light blue color depending on what light source you are looking at them with when they are off. The glass contains a rare-earth element that gives it this strange, changeable color. What the glass really does is filter out a narrow area of the yellow spectrum. This makes oranges and reds redder and sometimes greens and blues get a bit bluer. Caucasian people definitely look pinkish under these lamps. Because some of the spectrum has been filtered out, they give even less light per watt than standard incandescents.

The opposite of the long-life types is brighter and higher efficiency bulbs for projectors and photography. These have color temperatures as high as 3400 K and life spans as short as 6 hours. The blue photoflood is corrected to about 4800 K, slightly warmer than daylight, which is about 5500 K.

The most accurate artificial light source to judge colors with is the "color-corrected" bluish incandescent lamp, especially the blue photoflood. Their color when off resembles that of the "full spectrum" lamp above, but is more consistently a deeper blue to blue-green. This type of lamp is not commonly found in retail stores any longer. Because of the medium color filtration, these lamps are very inefficient. Note that I am not describing decorator lamps of any color, which only emit a single color.

Halogen lamps are a special type of incandescent lamp which is slightly more efficient than standard ones. Not much more, though. When first introduced, they were called quartz-iodine lamps which sounded rather scary. They are generally higher-current bulbs for autos as well as household types. They are ok where space is limited and the heat output is not a hazard. They are often shielded with a pyrex cover. This also gives some protection from their modest ultraviolet output. When installed, they should be handled with clean fingers and tissues, because fingerprints and dirt will cause the lamp to melt and fail. Avoid using tissues that have lotion manufactured into them. These lamps have a longer life than standard incandescent lamps of equal wattage and color temperature. Also, they do not blacken as much.

Incandescent lamps, especially lower-wattage ones, are very sensitive to vibration when on. The lowest-wattage ones, 4 watts, will break filaments easily even when off.

Special Night Lights

These use special aqua-green glow material or white LEDs (light-emitting diodes.) The aqua ones use only about 0.03 watt and may be left plugged in all the time. Over several years they gradually become dimmer.

The LED ones are about 1/2 to 1 watt and give more light than the green ones above. Some samples of these are poorly designed and they stop working after a few weeks. This means the LED has shorted out and must be replaced. If so and you are handy with electronic construction, you should also change the resistor as well as the LED in these from about 9,100 ohms, 1 watt, to about 22,000 ohms, 1 watt, flameproof type. They will then work for many years. White LEDs, like the above, gradually become dimmer over many months and years. It is best to leave these lamps plugged in all the time because their internal solder connections cannot withstand the stress of plugging and unplugging. You should unplug them, however, if you are plugging a large motorized appliance such as a vacuum cleaner into the same outlet set. Otherwise a voltage spike may destroy the LED night light.

Outdoor and Commercial Lamps

These include sodium-vapor (yellow-orange) lamps, metal-arc (white) lamps, and mercury-vapor lamps (bluish-green). The mercury-vapor lamp is the oldest of these types and is only about twice as efficient as an incandescent. All these lamps are generally too hot and too bright for residential interiors. Also they may require a glass enclosure to filter out their ultraviolet light. (The lamp envelope is often quartz which transmits ultraviolet.) They work better at low temperatures than fluorescent lamps.

LED cluster lamps are still new and expensive, but are now found in most traffic signals. They have nearly eliminated bulb changing, because LEDs last indefinitely if the current is not excessive. They save a lot of energy. They are becoming more common and less expensive for home use.

Neon and mercury-vapor sign lamps are driven by a high voltage transformer. Nowadays you will notice that they are kept behind a plastic shield for safety. The common reddish-orange sign lamp is neon.  The blue-green ones use mercury vapor. Other colors usually use mercury vapor with a fluorescent coating. As with other lamps, getting satisfactory life from them requires keeping the voltage, current and brightness to the minimum satisfactory amount.

Light Sources For Judging Colors - Summary

Most accurate - 1. Daylight with sunlight outside

2. Cloudy daylight or shade outside

3. Daylight through a window - may reduce blue fluorescence in washed clothes or brightened paper.

4. Color-corrected incandescent lamps

Less accurate - 5."Full Spectrum" or "Deluxe Cool White" compact or standard fluorescent lamps

6. Standard incandescent lamps - emphasize reds, and hard to tell navy blue from black

Poor - 6. Standard cool white, daylight, or warm white, compact or standard fluorescent lamps - some light reddish tones may look brownish

Unsatisfactory - 7. "Full-Spectrum" incandescent lamps and most outside lamp types,

 especially sodium or mercury vapor. Not sure about metal-arc.

It should be noted that all fluorescent lamps have a broken spectrum, known technically as a "line spectrum". For this reason

certain object colors can look quite different than they look by daylight.


Clothing colors can also look different in photographs, even with daylight, because digital sensors

or film often have have a steeper peak response than the eye in each of the primary colors

of blue, green, and red.

This can coincide with peaks or valleys in the spectrum of the clothing dyes. It's also possible for

some clothing to have a fluorescence in the blue or UV spectrum that can create a false blue

color in a photograph.



Updated Jan. 27, 2015