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16 mars 2011 3 16 /03 /mars /2011 03:34

A flash is a device used in photography producing a flash of artificial light (typically 1/1000 to 1/200 of a second) at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene. Other uses are capturing quickly moving objects or changing the quality of light. Flash refers either to the flash of light itself or to the electronic flash unit discharging the light. Most current flash units are electronic, having evolved from single-use flashbulbs and flammable powders. Modern cameras often activate flash units automatically.

Flash units are commonly built directly into a camera. Some cameras allow separate flash units to be mounted via a standardized "accessory mount" bracket (hot shoe). In professional studio equipment, flashes may be large, standalone units, or studio strobes, powered by special battery packs or connected to mains power   SONY VAIO VGN-FW21E Battery .

They are either synchronized with the camera using a flash synchronization cable or radio signal, or are light-triggered, meaning that only one flash unit needs to be synchronized with the camera, and in turn triggers the other units  SONY VAIO VGN-FW21J Battery .


The earliest flashes had of a quantity of thermite flash powder that was ignited by hand. Later, magnesium filaments were contained in flash bulbs, and electrically ignited by a contact in the camera shutter   SONY VAIO VGN-FW21L Battery ;

such a bulb could only be used once, and was too hot to handle immediately after use, but the confinement of what would otherwise have amounted to a small explosion was an important advance. An innovation was coating flashbulbs with a blue plastic coating to match the spectral quality to daylight balanced colour film and to make it look more moderate SONY VAIO VGN-FW21M Battery ,

as well as providing shielding for the bulb in the unlikely event of it shattering during the flash. Later bulbs substituted zirconium for the magnesium, which produced a brighter flash and tended to temporarily blind people  SONY VAIO VGN-FW21Z Battery .

Flashbulbs took longer to reach full brightness and burned for longer than electronic flashes. Slower shutter speeds (typically from 1/10 to 1/50 of a second) were used on cameras to ensure proper synchronization. A widely used flashbulb through the 1960s was the number 25  SONY VAIO VGN-FW25T/B Battery .

This is the large (approximately 1 inch (25 mm) in diameter) flashbulb often shown used by newspapermen in period movies, usually attached to a press camera or a twin-lens reflex camera  SONY VAIO VGN-FW26T/B Battery .

Flashcubes, Magicubes and Flipflash

In the late 1960s, Kodak improved their Instamatic camera line by replacing the individual flashbulb technology (used on early Instamatics) with theFlashcube  Dell Latitude E6400 battery,10400mAh,11.1V .

Flashcubes consisted of four electrically fired flashbulbs with an integral reflector in a cube-shaped arrangement that allowed taking four images in a row. A mechanism in the camera automatically rotated the flashcube 90 degrees to a fresh bulb upon advancing the film to the next exposure  Dell Latitude E6400 battery,10400mAh,11.1V .

The later Magicube (or X-Cube) retained the four-bulb format, and was superficially similar to the original Flashcube. However, the Magicube did not require electrical power- each bulb was set off by a plastic pin in the cube mount that released a cocked spring wire within the cube  Dell Latitude E6400 Battery,10400mAh/7800mAh .

This wire, in turn, struck a primer tube, at the base of the bulb, which contained a fulminate. The fulminate ignited shredded Zirconium foil in the flash and, thus, a battery was not required. Magicubes could also be fired by inserting a thin object, such as a key or paper clip, into one of the slots in the bottom of the cubeDell Latitude E6400 Battery,10400mAh/7800mAh.

Flashcubes and Magicubes are superficially similar but not interchangeable. Cameras requiring flashcubes have a round socket and a round hole for the flashcube's pin, while those requiring Magicubes have a round shape with protruding studs and a square socket hole for the Magicube's square pin Dell Latitude E6500 battery,10400mAh/7800mAh .

The Magicube socket can also be seen as an X, which accounts for its alternate name, X-Cube.

Another common flashbulb-based device was the Flipflash which included ten or so bulbs in a single unit  Dell Latitude E6500 battery,10400mAh/7800mAh .

The name derived from the fact that once half the flashes had been used up, the unit had to be flipped and re-inserted to use the remainder.

Modern flash technology

Today's flash units are often electronic flashtubes  Dell Latitude E6500 battery,10400mAh/7800mAh.

An electronic flash contains a tube filled with xenon gas, where electricity of high voltage is discharged to generate an electrical arc that emits a short flash of light. (A typical duration of the light impulse is 1/1000 second.) As of 2003, the majority of cameras targeted for consumer use have an electronic flash unit built in  Dell Latitude E6500 battery,10400mAh/7800mAh .

Another type of flash unit are microflashes, which are high-voltage flash units discharging a flash of light with an exceptionally quick, sub-microsecond duration. These are commonly used by scientists or engineers for examining extremely fast moving objects or reactions  HP Pavilion DV7 battery , 7200mAh ,

famous for producing images of bullets tearing through objects like lightbulbs or balloons (see Harold Eugene Edgerton).

Studio flashes usually contain a modeling light, an incandescent lightbulb close to the flash tube. The continuous illumination of a modeling light helps in visualizing the effect of the flash  HP Pavilion DV6-1210SA battery - 5200mAh/8800mAh .

The strength of a flash device is often indicated in terms of a guide number, despite the fact that the published guide numbers of different units can not necessarily be directly compared. The strength of larger studio flash units, such as monolights are indicated in watt-seconds  SONY VAIO VGN-FW27/B Battery .

Flash intensity

Unlike flashbulbs, the intensity of an electronic flash can be adjusted on some units. Small flash units typically vary the length of time of the discharge, larger (studio) units typically charge the capacitor less   SONY VAIO VGN-FW27/W Battery .

The disadvantage of charging the capacitor less is that the color temperature may change, necessitating corrections. With advances in semiconductor technology, there are some monolight (studio) units which can vary the time of the discharge  SONY VAIO VGN-FW31ZJ Battery .

The flash duration is typically described with two numbers: t.5 is the length of time for which the flash impulse is above 0.5 (50%) of the peak intensity, while t.1 is the length of time for which the impulse is above 0.1 (10%) of the peak (t.3 of course, would be above 30%)  SONY VAIO VGN-FW27T/H Battery .

For instance, t.5 can be 1/1200 sec whereas t.1 can be 1/450 sec for the same flash at the same intensity. For a small flash controlling intensity by time, the t.5 and t.1 numbers decrease as the intensity decreases. On flash units controlling intensity by capacitor charge   SONY VAIO VGN-FW29/B Battery ,

the t.5 and t.1 numbers increase as the intensity decreases (i.e. takes longer for the capacitor to discharge to that point). These times become important if a person wants to freeze action with the flash (as in sports)   SONY VAIO VGN-FW290JRB Battery .

Flash intensity is typically measured in stops or in fractions (1, 1/2, 1/4, 1/8 etc.). Some monolights display an "EU Number", so that a photographer can know the difference in brightness between different flash units with different watt-second ratings. EU10.0 is defined as 6400 Watt-seconds, and EU9.0 is one stop lower, i.e. 3200 watt-seconds  SONY VAIO VGN-FW290JTB Battery .

LED Flash (Illumination)

Although they are not yet at the power levels to replace xenon flash devices in still cameras, LEDs (specifically, high current flash LEDs) have recently been used as flash sources in camera phones   SONY VAIO VGN-FW290JTH Battery .

LEDs are expected to approach the power levels of xenon in the near future and may replace built-in xenon flashes in still cameras. The major advantages of LEDs over xenon include low voltage operation, higher efficiency and extreme miniaturization  SONY VAIO VGN-FW33G/E1 Battery .

Focal plane shutter synchronization

Electronic flash units have compatibility issues with focal plane shutters. Focal plane shutters expose using two curtains that cross the sensor. The first one opens and then the second curtain follows it after a delay equal to the nominal shutter speed SONY VAIO VGN-FW33G/W Battery .

A typical modern focal plane shutter takes about 1/200s to cross the sensor, so at speeds shorter than this only part of the sensor is uncovered at any one time. Electronic flash can have durations as short as 50 µs, so at speeds above the shutter traverse time only part of the sensor is exposed  SONY VAIO VGN-FW33GW Battery .

This limits the shutter speed to about 1/200s when using flash.

High-end flash units address this problem by offering a mode, typically called FP sync or HSS (High Speed Sync), which fires the flash tube multiple times during the time the slit traverses the sensor  (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

Such units require communication with the camera and are thus dedicated to a particular camera make. The multiple flashes result in a significant decrease in guide number, since each is only a part of the total flash power, but it's all that illuminates any particular part of the sensor  Dell Studio XPS 1640 Battery .

In general, if s is the shutter speed, and t is the shutter traverse time, the guide number reduces by ?s / t. For example, if the guide number is 100, and the shutter traverse time is 5 ms (a shutter speed of 1/200s), and the shutter speed is set to 1/2000s (0.5 ms), the guide number reduces by a factor of?0.5 / 5, or about 3.16, so the resultant guide number at this speed would be about 32 Dell Vostro 1710 Battery .

In fact, current (2010) flash units frequently have much lower guide numbers in HSS mode than in normal modes, even at speeds below the shutter traverse time. For example, the Mecablitz 58 AF-1 digital flash unit has a guide number of 58 in normal operation, but only 20 in HSS mode, even at low speeds  Dell KM958 battery .


As well as dedicated studio use, flash may be used as the main light source where ambient light is inadequate, or as a supplementary source in more complex lighting situations. Basic flash lighting produces a hard, frontal light unless modified in some way  Dell Studio 1555 battery .

Umbrellas and softboxes are commonly used for this purpose (even with small hand-held flash units).

Fill flash or "fill-in flash" describes flash used to supplement ambient light in order to illuminate a subject close to the camera that would otherwise be in shade relative to the rest of the scene   Sony VGP-BPS13 battery .

The flash unit is set to expose the subject correctly at a given aperture, while shutter speed is calculated to correctly expose for the background or ambient light at that aperture setting   Sony VGP-BPS13/B battery .

Bounce flash is a related technique in which flash is directed onto a reflective surface, for example a white ceiling or a flash umbrella, which then reflects light onto the subject. It can be used as fill-flash or, if used indoors, as ambient lighting for the whole scene  Sony VGP-BPS13/S battery .

Bouncing creates softer, less artificial-looking illumination than direct flash, often reducing overall contrast and expanding shadow and highlight detail, and typically requires more flash power than direct lighting   Sony VGP-BPS13A/B battery .

Part of the bounced light can be also aimed directly on the subject by "bounce cards" attached to the flash unit which increase the efficiency of the flash and illuminate shadows cast by light coming from the ceiling. It's also possible to use one's own palm for that purpose  Sony VGP-BPS13B/B battery ,

resulting in warmer tones on the picture, as well as eliminating the need to carry additional accessories.

Also, slave flash units exist that are set up away from the subject and camera, that are triggered by the light from the master flash. This slave flash provides fill or bounce light  Sony VGP-BPL9 battery .

Many small flashes and studio monolights have optical slaves built in. Wireless radio transmitters, such as Pocket Wizards are also popular for remote synchronization since the receiver unit can be around a corner, or well over 100 meters away (which would be far to difficult to trigger using an optical sync)  Sony VGP-BPS13B/B battery .

Another method that can be used is strobe. Some high end units can be set to flash a specified number of times at a specified frequency. This allows action to be frozen multiple times in a single exposure.

Colored gels can also be used to change the color of the flash  Sony VGP-BPL15 battery .

Correction gels are commonly used, so that the light of the flash would be the same as the tungsten lights (using a CTO gel) or the fluorescent lights   Dell Inspiron E1505 battery .


  • Using on-camera flash will give a very harsh light, which results in a loss of shadows in the image, because the only lightsource is in practically the same place as the camera. Balancing the flash power and ambient lighting or using off-camera flash can help overcome these issues    Dell Latitude E6400 battery .
  • Using an umbrella or softbox (the flash will have to be off-camera for this) makes softer shadows.
  • A typical problem with cameras using built-in flash units is the low intensity of the flash; the level of light produced will often not suffice for good pictures at distances of over 3 meters (10 ft) or so   HP Pavilion dv6000 Battery .
  • Dark, murky pictures with excessive image noise or "grain" will result. In order to get good flash pictures with simple cameras, it is important not to exceed the recommended distance for flash pictures. Larger flashes, especially studio units and monoblocks   HP Pavilion dv8000 battery ,
  • have sufficient power for larger distances, even through an umbrella, and can even be used against sunlight, at short distances.
  • The "Red-eye effect" is another problem with on camera and ring flash units   HP PAVILION DV6000 Battery,  8800mAh, 10.8V .
  • Since the retina of the human eye reflects red light straight back in the direction it came from, pictures taken from straight in front of a face often exhibit this effect. It can be somewhat reduced by using the "red eye reduction" found on many cameras (a pre-flash that makes the subject's irises contract)  HP PAVILION DV8000 Battery,  8800mAh, 10.8V .
  • However, very good results can be obtained only with a flash unit that is separated from the camera, sufficiently far from the optical axis, or by using bounce flash, where the flash head is angled to bounce light off a wall, ceiling or reflector SONY VAIO VGN-FZ Battery .
  • On some cameras the flash exposure measuring logic fires a pre-flash very quickly before the real flash. In some camera/people combinations this will lead to shut eyes in every picture taken. The blink response time seems to be around 1/10 of a second  HP Pavilion DV6000 battery - 8800mAh .
  • If the exposure flash is fired at approximately this interval after the TTL measuring flash, people will be squinting or have their eyes shut. One solution may be the FEL (flash exposure lock) offered on some more expensive cameras HP Pavilion DV8000 battery - 7800mAh ,
  • which allows the photographer to fire the measuring flash at some earlier time, long (many seconds) before taking the real picture. Unfortunately many camera manufacturers do not make the TTL pre-flash interval configurable  HP Pavilion DV6000 battery - 8800mAh .
  • Flash distracts people, limiting the number of pictures that can be taken without irritating them.
  • Photographing with flash may not be permitted in some museums even after purchasing a permit for taking pictures HP Pavilion DV8000 battery - 6600mAh .
  • Flash equipment may take some time to setup, and like any grip equipment, may need to be carefully secured, especially if hanging overhead so it does not fall on anyone. A small breeze can easily topple a flash with an umbrella on a lightstand if it is not tied down or sandbagged SONY VAIO VGN-FZ Battery .
  • Larger equipment (e.g. monoblocks) will need a supply of A.C. power.

A ring flash, invented by Lester A. Dine in 1952, originally for use in dental photography , is a circular photographic flash that fits around the lens, especially for use in macro (or close-up) photography  SONY VAIO VGN-FZ18 Battery .

Its most important characteristic is providing even illumination with few shadows visible in the photograph, as the origin of the light is very close to (and surrounds) the optical axis of the lens. When the subject is very close to the camera, as is the case in macro photography, the distance of the flash from the optical axis becomes significant  SONY VAIO VGN-FZ21E Battery .

For objects close to the camera, the size of the ring flash is significant and so the light encounters the subject from many angles in the same way that it does with a conventional flash with soft box. This has the effect of further softening any shadows SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

Ring flashes are also very popular in portrait and fashion photography. In addition to softening shadows, the unique way that a ring flash renders light gives the model a shadowy halo which is a common feature of fashion photography  SONY VAIO VGN-FW31J Battery - 5200mAh/7800mAh/10400mAh, 11.10V .

Macro ring flash usually consists of two parts: a shoe-mount unit mounted on a hot shoe, and a circular flash unit mounted on the front of a lens. Power is supplied by batteries in the shoe-mount unit, and a cord relays the power and control signals to the circular flash unit  SONY VAIO VGN-FW21E Battery .

For larger ring flash units like those used for fashion photography, power is usually delivered by a power pack which can be battery or AC powered. Some ring flashes however, like ones made by Alien Bees, are constructed like mono lights where the light and power are contained in one unit  SONY VAIO VGN-NR11S/S Battery .

Within the circular flash unit, there can be one or more flash tubes, each of which can be turned on or off individually. Some ring flashes have focusing lamps for helping low-light focusing. Also available are ring flash diffusers, which have no light source of their own   SONY VAIO VGN-NR11M/S Battery ,

but instead mount in front of a conventional flash unit and transmit the light to a ring-shaped diffuser at the front of the lens.

There are also specialty (passive) light modifiers, which will shape the light from an ordinary (shoe mount) flash into that of a ring flash   SONY VAIO VGN-NR11Z/S Battery .

The adapters use a series of diffusers and reflectors to "bend" the light around the lens axis. The light is then emitted from that axis. This maintains any TTL lighting functions that may be shared by the camera and flash, as the actual light source has not changedSONY VAIO VGN-NR11Z/T Battery .

Ring flash as a lighting technique has enjoyed a strong resurgence over the last few years, as photographers realize that it is far more useful than the one-look way in which it has been used for decades. Specifically, it is now being used primarily as a fill light to raise the illumination level of shadows created by other, off-axis lights   Sony VAIO VGN-FZ21E Battery .

It is considered to be a particularly good source of fill light because it does not create its own new set of shadows.

Through-the-lens (TTL) metering is a photographic term describing a feature of cameras capable of measuring light levels in a scene through their taking lenses, as opposed to a separate metering window  Sony VAIO VGN-FW21E Battery .

This information can then be used to select a proper exposure (average luminance), and control the amount of light emitted by a flash connected to the camera.

Through-the-lens metering is most often associated with single-lens reflex (SLR) cameras  Sony VAIO VGN-NR11S/S Battery .

A light sensor can be incorporated into the pentaprism or pentamirror, the mechanism by which an SLR allows the viewfinder to see directly out the lens. However, TTL metering systems have been incorporated into other types of cameras. All digital "point-and-shoot cameras" use TTL metering, performed by the imaging sensor itself   Sony VAIO VGN-NR11Z/S Battery .

With digital SLR cameras, the metering is typically carried out by a metering/autofocus module located at the bottom of the mirror chamber, underneath the mirror, however other methods exists as well. Sony's 'SLT' cameras use a fixed semi-transparent mirror to bounce a small part of the light towards the autofocus and light metering module, located at the top of the camera Sony VAIO VGN-NR11M/S Battery .

In more advanced modern cameras multiple 'segments' are used to acquire the amount of light in different places of the picture. Depending on the mode the photographer has selected, this information is then used to correctly set the exposure. With a simple spot meter, a single spot on the picture is selected   Sony VAIO VGN-NR11Z/T Battery .

The camera sets the exposure in order to get that particular spot properly exposed. With multiple segment metering (also known as matrix metering), the values of the different segments are combined and weighted to set the correct exposure   SONY VAIO VGN-FZ180E Battery .

Implementations of these metering modes vary between cameras and manufacturers, making it difficult to predict how a scene will be exposed when switching cameras.

Through the lens flash metering

The process of calculating the correct amount of flash light can also be done 'through the lens'  SONY VAIO VGN-FZ220E Battery .

This is being done in a significantly different way than non-flash 'through the lens' metering. The actual metering itself happens in two different ways, depending on the medium. Digital TTL works differently than analog TTL.

The analog version of TTL works as follows: when the incoming light hits the film, a part of it is reflected towards a sensor SONY VAIO VGN-FZ340E Battery .

This sensor controls the flash. If enough light is captured, the flash is stopped. The biggest problem here is the film; not all brands and types reflect the light to the same amount. Nevertheless, this method of flash metering is more advanced than those previously usedSONY VAIO VGN-FZ430E Battery .

With digital, this way of metering is not possible any more since a CMOS or CCD chip, used to collect the light, is not reflective enough. There are a few older digital cameras which still use the analog technique, but these are getting rare. The Fujifilm S1 and S3 are the most known to use this technique  SONY VAIO VGN-FZ460E Battery .

Digital TTL works as follows: Before the actual exposure one or more small flashes, called "preflashes", are emitted. The light returning through the lens is measured and this value is used to calculate the amount of light necessary for the actual exposure  SONY VAIO VGN-FZ480E Battery .

Multiple pre-flashes can be used to improve the flash output . Canon refers to this technique as "E-TTL" and has later improved the system with "E-TTL II". The first form of digital TTL by Nikon, called "D-TTL", was used in a few early models. Since then, the superior "i-TTL" system has been used  SONY VAIO VGN-FZ4000 Battery .

When using front-curtain flash (when the flash fires immediately after the shutter opens), the preflashes and main flash appear as one to the human eye, since there is very little time between them. When using rear-curtain flash (when the flash fires at the end of the exposure) and a slow shutter speed   SONY VAIO VGN-FZ31E Battery ,

the distinction between the main flash and the preflashes is more obvious.

Some cameras and flash units take more information into account when calculating the necessary flash output, including the distance of the subject to the lens   SONY VAIO VGN-FZ31B Battery .

This improves the lighting when a subject is placed in front of a background. If the lens is focused on the subject, the flash will be controlled to allow for proper exposure on the subject, thus leaving the background underexposed    SONY VAIO VGN-FZ31J Battery.

Alternatively, if the lens is focused on the background, the background will be properly exposed, leaving the subject in the foreground typically overexposed. This technique requires both a camera capable of calculating the distance information, as well as the lens being capable of communicating the focal distance to the body   SONY VAIO VGN-FZ31M Battery .

Nikon refers to this technique as "3D matrix metering", although different camera manufacturers use different terms for this technique. Canon incorporated this technique in E-TTL II.

More advanced TTL flash techniques include off-camera flash lighting, where one or more flash units are located at different locations around the subject  SONY VAIO VGN-FZ31Z Battery .

In this case a 'commander' unit (which can be integrated in the camera body) is used to control all of the remote units. The commander unit usually controls the remote flashes by using flashes of visible or infrared light, although TTL-capable radio triggering systems are available   SONY VAIO VGN-FZ38M Battery .

The photographer can normally vary the light ratios between the different flashes. The technique of using preflashes to get a proper exposure is still used in automatic flash modes   SONY VGP-BPS8 Battery .

A compact fluorescent lamp (CFL), also known as a compact fluorescent light or energy saving light (or less commonly as a compact fluorescent tube), is a type of fluorescent lamp. Many CFLs are designed to replace an incandescent lamp and can fit into most existing light fixtures formerly used for incandescents  SONY VGP-BPS13/S Battery .

Compared to general service incandescent lamps giving the same amount of visible light, CFLs use less power and have a longer rated life. In the United States, a CFL has a higher purchase price than an incandescent lamp, but can save over US$40 in electricity costs over the lamp's lifetime      SONY VGP-BPS13A/B Battery .

Like all fluorescent lamps, CFLs contain mercury, which complicates their disposal.

CFLs radiate a different light spectrum from that of incandescent lamps  SONY VGP-BPS13B/B Battery .

Improved phosphor formulations have improved the perceived colour of the light emitted by CFLs such that some sources rate the best "soft white" CFLs as subjectively similar in colour to standard incandescent lamps  SONY VGP-BPS13A/S Battery .

The parent to the modern fluorescent lamp was invented in the late 1890s by Peter Cooper Hewitt. The Cooper Hewitt lamps were used for photographic studios and industries.

Edmund Germer, Friedrich Meyer, and Hans Spanner then patented a high pressure vapor lamp in 1927  SONY VGP-BPS13AS Battery.

George Inman later teamed with General Electric to create a practical fluorescent lamp, sold in 1938 and patented in 1941.Circular and U-shaped lamps were devised to reduce the length of fluorescent light fixtures. The first fluorescent bulb and fixture were displayed to the general public at the 1939 New York World's Fair  Dell Inspiron 1320n Battery .

The spiral tube CFL was invented in 1976 by Edward E. Hammer, an engineer with General Electric, in response to the 1973 oil crisis. The design met its goals, and it would have cost GE only about US$25 million to build new factories to produce them, but the invention was shelved  Dell Inspiron 1464 Battery .

The design was eventually copied by others. It was not until 1995 that spiral lamps manufactured in China were commercially available; spiral lamps have steadily increased in sales volume.

In 1980, Philips introduced its model SL, which was a screw-in lamp with integral ballast   Dell Inspiron 1564 Battery .

The lamp used a folded T4 tube, stable tri-color phosphors, and a mercury amalgam. This was the first successful screw-in replacement for an incandescent lamp. In 1985 Osram started selling their model EL lamp which was the first CFL to include an electronic ballast  Dell Inspiron 1764 Battery .

Development of fluorescent lamps that could fit in the same volume as comparable incandescent lamps required the development of new, high-efficacy phosphors that could withstand more power per unit area than the phosphors used in older, larger fluorescent tubes  Dell Studio 1450 Battery .

The most important technical advance has been the replacement of electromagnetic ballasts with electronic ballasts; this has removed most of the flickering and slow starting traditionally associated with fluorescent lighting  Dell Studio 1457 Battery .

There are two types of CFLs: integrated and non-integrated lamps. Integrated lamps combine a tube, an electronic ballast and either an Edison screw or abayonet fitting in a single unit. These lamps allow consumers to replace incandescent lamps easily with CFLs Dell Latitude D610 Battery .

Integrated CFLs work well in many standard incandescent light fixtures, reducing the cost of converting to fluorescent. Special 3-way models and dimmable models with standard bases are available   Toshiba NB100 Battery .

Non-integrated CFLs have the ballast permanently installed in the luminaire, and only the lamp bulb is usually changed at its end of life. Since the ballasts are placed in the light fixture they are larger and last longer compared to the integrated ones, and they don't need to be replaced when the bulb reaches its end-of-life  Toshiba Satellite M65 battery .

Non-integrated CFL housings can be both more expensive and sophisticated. They have two types of tubes: a bi-pin tube designed for a conventional ballast, and a quad-pin tube designed for an electronic ballast or a conventional ballast with an external starter  Toshiba Satellite M60 battery .

A bi-pin tube contains an integrated starter which obviates the need for external heating pins but causes incompatibility with electronic ballasts.


CFLs have two main components: a gas-filled tube (also called bulb or burner) and a magnetic or electronic ballast  Dell Latitude D830 Battery .

For their principles of operation, seeFluorescent lamp.

Standard shapes of CFL tube are single-turn double helix, double-turn, triple-turn, quad-turn, circular, and butterfly  Dell Latitude D620 Battery .

Electronic ballasts contain a small circuit board with rectifiers, a filter capacitor and usually two switching transistors connected as a high-frequency resonant series DC to AC inverter. The resulting high frequency, around 40 kHz or higher, is applied to the lamp tubeDell Inspiron Mini 10 Battery .

Since the resonant converter tends to stabilize lamp current (and light produced) over a range of input voltages, standard CFLs do not respond well in dimming applications and special lamps are required for dimming service. CFLs that flicker when they start have magnetic ballasts; CFLs with electronic ballasts are now much more common  Sony VGN-FW11S Battery .

CFL power sources

CFLs are produced for both alternating current (AC) and direct current (DC) input. DC CFLs are popular for use in recreational vehicles and off-the-gridhousing   Sony VGN-FW11M Battery .

There are various aid agency led initiatives in developing countries to replace kerosene lanterns (with their associated health hazards) with DC CFLs (with car batteries and small solar panels or wind generators)  Sony VGN-FW139E/H battery .

CFLs can also be operated with solar powered street lights, using solar panels located on the top or sides of a pole and light fixtures that are specially wired to use the lamps  Dell Latitude E5400 Battery .


The average rated life of a CFL is between 8 and 15 times that of incandescents. CFLs typically have a rated lifespan of between 6,000 and 15,000 hours, whereas incandescent lamps are usually manufactured to have a lifespan of 750 hours or 1,000 hours  Dell Latitude E4200 Battery .

The lifetime of any lamp depends on many factors including operating voltage, manufacturing defects, exposure to voltage spikes, mechanical shock, frequency of cycling on and off, lamp orientation, and ambient operating temperature, among other factors  Dell Inspiron 300M Battery .

The life of a CFL is significantly shorter if it is turned on and off frequently. In the case of a 5-minute on/off cycle the lifespan of a CFL can be reduced to "close to that of incandescent light bulbs". The U.S. Energy Star program suggests that fluorescent lamps be left on when leaving a room for less than 15 minutes to mitigate this problem  Dell Vostro A840 Battery .

CFLs produce less light later in their lives than when they are new. The light output decay is exponential, with the fastest losses being soon after the lamp is first used. By the end of their lives, CFLs can be expected to produce 70–80% of their original light output  Dell Studio 1737 battery .

The response of the human eye to light islogarithmic (a photographic "f-stop" reduction represents a halving in actual light, but is subjectively quite a small change). A 20–30% reduction over many thousands of hours represents a change of about half an f-stopDell Inspiron E1505 battery .

So, presuming the illumination provided by the lamp was ample at the beginning of its life, such a difference will be compensated for by the eyes, for most purposes  Dell RM791 battery .

For a given light output, CFLs use 20 to 33 percent of the power of equivalent incandescent lamps. Since lighting accounted for approximately 9% of household electricity usage in the United States in 2001, widespread use of CFLs could save as much as 7% of total U.S. household usage  Dell XPS M1530 battery .

Heating and cooling

If a building's indoor incandescent lamps are replaced by CFLs, the heat produced due to lighting is significantly reduced  Dell XPS M2010 battery .

In warm climates or in office or industrial buildings where air conditioning is often required, CFLs would reduce the load on the cooling system when compared to the use of incandescent lamps, resulting in savings in electricity, in addition to the energy efficiency savings of using CFLs instead of incandescent lamps  Acer Aspire One battery .

However, in cooler climates in which buildings require heating, the heating system will need to replace the inadvertently generated heat. While the CFLs are still saving electricity, total greenhouse gas emissions may increase in certain scenarios, such as the operation of a natural gas furnace to replace the unintended heating from CFLs running on low-GHG electricity Toshiba Satellite P10 Battery .

In Winnipeg, Canada, it is estimated that CFLs will only generate 17% savings in energy when switching from incandescent bulbs, as opposed to the 75% savings that can be expected if there were no heating or cooling considerations   SONY VGN-FZ210CE Battery .

Efficacy and efficiency

Because the eye's sensitivity changes with the wavelength, the output of lamps is commonly measured in lumens, a measure of the power of light perceived by the human eye      Dell Precision M70 Battery .

The luminous efficacy of lamps refers to the number of lumens produced for each watt of electrical power used. A theoretically 100% efficient electric light source producing light only at the wavelength the human eye is most sensitive to would produce 680 lumens per watt  Toshiba Satellite L305 Battery .

The typical luminous efficacy of CFL lamps is 60 to 72 lumens per watt,  and that of normal domestic incandescent lamps is 13 to 18 lm/W. Compared to the theoretical 100% efficient lamp, these figures are equivalent to lighting efficiency ranges of 9 to 11% for CFLs (60/680 and 72/680) and 1.9 to 2.6% for incandescents (13/680 and 18/680)  Toshiba Satellite T4900 Battery .

Embodied energy

While CFLs require more energy in manufacturing than incandescent lamps, this embodied energy is offset by their longer life and lower energy use than equivalent incandescent lamps  Toshiba PA3399U-2BRS battery .


While the purchase price of an integrated CFL is typically 3 to 10 times greater than that of an equivalent incandescent lamp, the extended lifetime and lower energy use will more than compensate for the higher initial cost  Toshiba Satellite A200 Battery .

A U.S. article stated "A household that invested $90 in changing 30 fixtures to CFLs would save $440 to $1,500 over the five-year life of the bulbs, depending on your cost of electricity. Look at your utility bill and imagine a 12% discount to estimate the savingsToshiba Satellite 1200 Battery ."

CFLs are extremely cost-effective in commercial buildings when used to replace incandescent lamps. Using average U.S. commercial electricity and gas rates for 2006, a 2008 article found that replacing each 75 W incandescent lamp with a CFL resulted in yearly savings of $22 in energy usage, reduced HVAC cost, and reduced labour to change lamps Toshiba Satellite M300 Battery .

The incremental capital investment of $2 per fixture is typically paid back in about one month. Savings are greater and payback periods shorter in regions with higher electric rates and, to a lesser extent, also in regions with higher than U.S. average cooling requirements  SONY VGP-BPS13A/Q Battery .

The current price of CFLs reflects the manufacturing of nearly all CFLs in China, where labour costs less. In September 2010, the Winchester, Virginia General Electric plant closed, leaving Osram Sylvania the last company to make standard incandescent bulbs in the United States  SONY VGP-BPS13A/Q Battery .

At that time, Ellis Yan, whose Chinese company made the majority of CFLs sold in the United States, was interested in building a United States factory to make CFL bulbs, but he needed $12.5 million to do so, and the U.S. government had not helped with this  SONY VGP-BPS13B/Q Battery .

Yan said stores wanted American-made bulbs, which would be 45 to 50 cents more each, but Yan said consumers were willing to pay this much.

General Electric had considered changing one of its bulb plants to make CFLs, but even after a $40 million investment, wage differences would mean the bulbs would cost one and a half times those made in China  SONY VGP-BPS13B/Q Battery .

Comparison with alternative technologies

Solid-state lighting has already filled a few specialist niches such as traffic lights and may compete with CFLs for house lighting as well. LEDs providing over 200 lm/W have been demonstrated in laboratory tests  and expected lifetimes of around 50,000 hours are typical  SONY VGP-BPS13/Q Battery .

The luminous efficacy of available LED lamps does not typically exceed that of CFLs, though there have been LED lamps with 75 lm/W overall luminous efficacy at least since autumn 2009. DOE testing of commercial LED lamps designed to replace incandescent or CFL lamps showed that average efficacy was still about 31 lm/W in 2008   SONY VGP-BPS13/Q Battery .

General Electric discontinued a 2007 development project intended to develop a high-efficiency incandescent bulb with the same lumens per watt as fluorescent lamps. Meanwhile other companies have developed and are selling halogen incandescents that use 70% of the energy of standard incandescents  SONY VGP-BPS21A/B Battery .

Other CFL technologies

Another type of fluorescent lamp is the electrodeless lamp, known as magnetic induction lamp, radiofluorescent lamp or fluorescent induction lamp   SONY VGP-BPS21/S Battery .

These lamps have no wire conductors penetrating their envelopes, and instead excite mercury vapour using a radio-frequency oscillator.Currently, this type of light source is struggling with a high cost of production, stability of the products produced by domestic manufacturers in China, establishing an internationally recognized standard and problems with EMC and RFI SONY VGP-BPS21B Battery .

Furthermore, induction lighting is excluded from Energy Star standard for 2007 by the EPA.

The cold cathode fluorescent lamp (CCFL) is one of the newest forms of CFL. CCFLs use electrodes without a filament  SONY VGP-BPS21A Battery .

The voltage of CCFLs is about 5 times higher than CFLs, and the current is about 10 times lower. CCFLs have a diameter of about 3 millimeters. CCFLs were initially used for document scanners and also for back-lighting LCD displays, but they are now also manufactured for use as lamps   SONY VGP-BPS21 Battery .

The efficacy (lumens per watt) is about half that of CFLs. Their advantages are that they are instant-on, like incandescents, they are compatible with timers, photocells, and dimmers, and they have a long life of approximately 50,000 hours  Sony VGP-BPS21A/B Battery .

CCFLs are a convenient transition technology for those who are not comfortable with the short lag time associated with the initial lighting of CFLs. They are also an effective and efficient replacement for lighting that is turned on and off frequently with little extended use (e.g. a bathroom or closet)  Sony VGP-BPS21/S Battery .

A few manufacturers make CFL-style bulbs with mogul Edison screw bases intended to replace 250 watt and 400 watt metal halide lamps, claiming a 50% energy reduction; however, these lamps require slight rewiring of the lamp fixtures to bypass the lamp ballastSony VGP-BPS21A Battery .

Spectrum of light

CFLs emit light from a mix of phosphors inside the bulb, each emitting one band of colour. Modern phosphor designs are a compromise between the shade of the emitted light, energy efficiency, and cost  Sony VGP-BPS21 Battery .

Every extra phosphor added to the coating mix causes a loss of efficiency and increased cost. Good quality consumer CFLs use three or four phosphors to achieve a "white" light with a CRI (colour rendering index) of around 80, where 100 represents the appearance of colours under daylight or a black-body (depending on the correlated colour temperature) Sony Vaio PCG-5G2L Battery .

Colour temperature is a quantitative measure. The higher the number in kelvins, the more blue the shade. Colour names associated with a particular colour temperature are not standardized for modern CFLs and other tri-phosphor lamps like they were for the older-style halophosphate fluorescent lamps   Sony Vaio PCG-5G3L Battery .

Variations and inconsistencies exist among manufacturers. For example, Sylvania's Daylight CFLs have a colour temperature of 3,500 K, while most other lamps with a daylight label have colour temperatures of at least 5,000 K   Sony Vaio PCG-5J1L Battery .

Some vendors do not include the kelvin value on the package, but this is beginning to change now that the Energy Star criteria for CFLs is expected to require such labelling in its 4.0 revision.

Some manufacturers now label their CFLs with a 3-digit code to specify the colour rendering index (CRI) and colour temperature of the lamp  Sony Vaio PCG-5K2L Battery .

The first digit represents the CRI measured in tens of percent, while the second two digits represent the colour temperature measured in hundreds of kelvins. For example, a CFL with a CRI of 83 and a colour temperature of 2,700 K would be given a code of 827 Sony Vaio PCG-5J2L Battery

CFLs are also produced, less commonly, in other colours:

  • Red, green, orange, blue, and pink, primarily for novelty purposes
  • Blue for phototherapy  Sony Vaio PCG-5K1L Battery
  • Yellow, for outdoor lighting, because it does not attract insects
  • Black light (UV light) for special effects   Sony Vaio PCG-6S2L Battery

Black light CFLs, those with UVA generating phosphor, are much more efficient than incandescent black light lamps, since the amount of UV light that the filament of the incandescent lamp produces is only a fraction of the generated spectrum  Sony Vaio PCG-6S3L Battery .

Starting time

Incandescents reach full brightness a fraction of a second after being switched on. As of 2009, CFLs turn on within a second, but many still take time to warm up to full brightness  Sony Vaio PCG-6V1L Battery .

The light color may be slightly different immediately after being turned on.  Some CFLs are marketed as "instant on" and have no noticeable warm-up period, but others can take up to a minute to reach full brightness, or longer in very cold temperatures. Some that use a mercury amalgam can take up to three minutes to reach full output   Sony Vaio PCG-6W1L Battery .

This and the shorter life of CFLs when turned on and off for short periods may make CFLs less suitable for applications such as motion-activated lighting         Sony Vaio PCG-6W2L Battery .

Hybrid CFL

From November 2010 a Hybrid CFL as a solution for instant warm up time and brightness is commercially available.  A second company announced a similar product to be available during 2011   Sony Vaio PCG-6W3L Battery .

These products combine a halogen lamp with a CFL. The halogen lights immediately, and once the CFL has warmed up the halogen lamp goes out  Sony Vaio PCG-7111L Battery .

Health issues

The cost effectiveness of battery-powered CFLs is enabling aid agencies to support initiatives to replace kerosene lamps, the fumes from which cause chronic lung disorders in typical homes and work places in third world countries  Sony Vaio PCG-7112L Battery .

According to the European Commission Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) in 2008, the only property o

f compact fluorescent lamps that could pose an added health risk is the ultraviolet and blue light emitted by such devices  Sony Vaio PCG-7113L Battery .

The worst that can happen is that this radiation could aggravate symptoms in people who already suffer rare skin conditions that make them exceptionally sensitive to light. They also stated that more research is needed to establish whether compact fluorescent lamps constitute any higher risk than incandescent lamps  Sony Vaio PCG-7133L Battery .

If individuals are exposed to the light produced by some single-envelope compact fluorescent lamps for long periods of time at distances of less than 20 cm, it could lead to ultraviolet exposures approaching the current workplace limit set to protect workers from skin and retinal damage  Sony Vaio PCG-7Z2L Battery .

The UV radiation received from CFLs is too small to contribute to skin cancer and the use of double-envelope CFL lamps "largely or entirely" mitigates any other risks.

Mercury content

CFLs, like all fluorescent lamps, contain small amounts of mercury  as vapor inside the glass tubing. Most CFLs contain 3–5 mg per bulb, with the eco-friendly bulbs containing as little as 1 mg    Sony Vaio PCG-8Y1L Battery .

Because mercury is poisonous, even these small amounts are a concern for landfills and waste incinerators where the mercury from lamps may be released and contribute to air and waterpollution. In the U.S., lighting manufacturer members of the National Electrical Manufacturers Association (NEMA) have voluntarily capped the amount of mercury used in CFLs Sony Vaio PCG-8Y2L Battery .

In the EU the same cap is required by the RoHS law.

In areas with coal-fired power stations, the use of CFLs saves on mercury emissions when compared to the use of incandescent bulbsSony Vaio PCG-8Z1L Battery .

This is due to the reduced electrical power demand, reducing in turn the amount of mercury released by coal as it is burned.In July 2008 the U.S. EPA published a data sheet stating that the net system emission of mercury for CFL lighting was lower than for incandescent lighting of comparable lumen output  Sony Vaio PCG-8Z2L Battery .

This was based on the average rate of mercury emission for U.S. electricity production and average estimated escape of mercury from a CFL put into a landfill. Coal-fired plants also emit other heavy metals, sulphur, and carbon dioxide  SONY VAIO VGN-FW31J Battery .

In the United States, the U.S. Environmental Protection Agency estimated that if all 270 million compact fluorescent lamps sold in 2007 were sent to landfill sites, that this would represent around 0.13 metric tons, or 0.1% of all U.S. emissions of mercury (around 104 metric tons that year)  SONY VAIO VGN-FW31E Battery .

Health and environmental concerns about mercury have prompted many jurisdictions to require spent lamps to be properly disposed or recycled rather than being included in the general waste stream sent to landfills. It is unlawful to dispose of fluorescent bulbs as universal waste in the states of California, Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin  SONY VAIO VGN-FW31B Battery .

In the European Union, CFLs are one of many products subject to the WEEE recycling scheme. The retail price includes an amount to pay for recycling, and manufacturers and importers have an obligation to collect and recycle CFLs. Safe disposal requires storing the bulbs unbroken until they can be processed  SONY VAIO VGN-FW31M Battery .

In the U.S., The Home Depot is the first retailer to make CFL recycling options widely available.

Special handling instructions for breakage are currently not printed on the packaging of household CFL bulbs in many countries  SONY VAIO VGN-FW31Z Battery .

The amount of mercury released by one bulb can temporarily exceed U.S. federal guidelines for chronic exposure. Chronic however, implies that the exposure continues constantly over a long period of time and the Maine DEP study noted that it remains unclear what the health risks are from short-term exposure to low levels of elemental mercury SONY VAIO VGN-FW38M Battery .

The Maine DEP study also confirmed that, despite following EPA best-practice cleanup guidelines on broken CFLs, researchers were unable to remove mercury from carpet, and agitation of the carpet — such as by young children playing — created localized concentrations as high as 25,000 ng/m3 in air close to the carpet, even weeks after the initial breakage SONY VAIO VGN-AW41JF Battery .

Conventional tubular fluorescent lamps have been in commercial and domestic use since the 1930s with little public concern about their handling; these and other domestic products, such as the mercury-in-glass thermometer — now banned by many countries for medical use — contain far more mercury than modern CFLs   SONY VAIO VGN-AW41JF/H Battery .

The U.S. Environmental Protection Agency (EPA) recommends that, in the absence of local guidelines, fluorescent bulbs be double-bagged in plastic before disposal. The Maine DEP study of 2008 compared clean-up methods, and warned that the EPA recommendation of plastic bags was the worst choice, as vapors well above safe levels continued to leach from the bags  SONY VAIO VGN-AW41MF Battery .

The Maine DEP now recommends a sealed glass jar as the best repository for a broken bulb.

According to the Northwest Compact Fluorescent Lamp Recycling Project, because household users in the U.S. Northwest have the option of disposing of these products in the same way they dispose of other solid waste   SONY VAIO VGN-AW41MF/H Battery ,

in Oregon "a large majority of household CFLs are going to municipal solid waste". They also note the EPA's estimates for the percentage of fluorescent lamps' total mercury released when they are disposed of in the following ways: municipal waste landfill 3.2%, recycling 3%, municipal waste incineration 17.55% and hazardous waste disposal 0.2% SONY VAIO VGN-FW30B Battery .

Mercury poisoning of Chinese factory workers

In the past decade, hundreds of Chinese factory workers who manufacture CFLs for export to first world countries were being poisoned and hospitalized because of mercury exposure  SONY VAIO VGN-FW50B Battery .

Examples include workers at the Nanhai Feiyang lighting factory in Foshan, where 68 out of 72 were so badly poisoned that they required hospitalization. At another CFL factory in Jinzhou, 121 out of 123 employees were found to have excessive mercury levels, with one employee's mercury level 150 times the accepted standard  SONY VAIO VGN-FW51B/W Battery .


The first step of processing CFLs involves crushing the bulbs in a machine that uses negative pressure ventilation and a mercury-absorbing filter or cold trap to contain mercury vapor   SONY VAIO VGN-FW51MF Battery .

Many municipalities are purchasing such machines. The crushed glass and metal is stored in drums, ready for shipping to recycling factories.

Greenhouse gases

In some parts of the world, e.g., Quebec and British Columbia, central heating for homes is provided by the burning of natural gas, whereas electricity is primarily provided by hydroelectric or nuclear power  SONY VAIO VGN-FW51MF/H Battery .

In such areas, heat generated by conventional electric light bulbs significantly reduces the release of greenhouse gases from the natural gas. Ivanco, Karney, and Waher estimate that "If all homes in Quebec were required to switch from (incandescent) bulbs to CFLs    SONY VAIO VGN-FW51ZF Battery ,

there would be an increase of almost 220,000 tonnes in CO2 emissions in the province, equivalent to the annual emissions from more than 40,000 automobiles."

Design and application issues

The primary objectives of CFL design are high electrical efficiency and durability   SONY VAIO VGN-FW51ZF/H Battery .

However, there are some other areas of CFL design and operation that are problematic:

CFL light output is roughly proportional to phosphor surface area, and high output CFLs are often larger than their incandescent equivalents. This means that the CFL may not fit well in existing light fixtures SONY VAIO VGN-FW52JB Battery .
End of life
In addition to the wear-out failure modes common to all fluorescent lamps, the electronic ballast may fail, since it has a number of component parts. Ballast failures may be accompanied by discolouration or distortion of the ballast enclosure, odours, smoke or flames   SONY VAIO VGN-FW54FB Battery .
The lamps are internally protected and are meant to fail safely at the end of their lives. Industry associations are working toward advising consumers of the different failure modes of CFLs compared to incandescent lamps, and to develop lamps with inoffensive failure modes  SONY VAIO VGN-FW70DB Battery .
New North American technical standards aim to eliminate smoke or excess heat at the end of lamp life.
Incandescent replacement wattage inflation
An August 2009 newspaper report described that some manufacturers claim the CFL replaces a higher wattage incandescent lamp than justified by the light produced by the CFL   SONY VAIO VGN-FW71DB/W Battery .
Equivalent wattage claims can be replaced by comparison of the lumens produced by the lamp.
Only some CF lamps are labeled for dimming control. Using regular CFLs with a dimmer is ineffective at dimming, can shorten bulb life and will void the warranty of certain manufacturers  SONY VAIO VGN-FW72JGB Battery .
Dimmable CFLs are available. There is a need for the dimmer switch used in conjunction with a dimmable CFL to be matched to its power consumption range, many dimmers installed for use with incandescent bulbs do not yield acceptable results below 40W, whereas CFL applications commonly draw power in the range 7-20W   SONY VAIO VGN-FW73JGB Battery .
The marketing and availability of dimmable CFLs has preceded that of suitable dimmers. The dimming range of CFLs is usually between 20% and 90%.However, in many modern CFLs the dimmable range has been improved to be from 2% to 100%, more akin to regular lights  SONY VAIO VGN-FW74FB Battery .
There are two types of dimmable CFL marketed: Regular dimmable CFLs, and "switch-dimmable" CFLs. The latter use a regular light switch, while the on-board electronics has a setting where the number of times the switch is turned on & off in quick succession sets a reduced light output mode   SONY VAIO VGN-FW81HS Battery .
Dimmable CFLs are not a 100% replacement for incandescent fixtures that are dimmed for "mood scenes" such as wall sconces in a dining area. Below the 20% limit, the lamp remain at the approximate 20% level, in other cases it may flicker or the starter circuitry may stop and restart   SONY VAIO VGN-FW81NS Battery .
Above the 80% dim limit, the bulb will generally glow at 100% brightness. However, these issues have been addressed with the latest units and some CFLs may perform more like regular incandescent lamps. Dimmable CFLs have a higher purchase cost than standard CFLs due to the additional circuitry required for dimming   SONY VAIO VGN-FW81S Battery .
A further limitation is that multiple dimmable CFLs on the same dimmer switch may not appear to be at the same brightness level. Cold Cathode CFLs can be dimmed to low levels, making them popular replacements for incandescent bulbs on dimmer circuits   SONY VAIO VGN-FW82DS Battery .
Perceived coldness of low intensity CFL
When a CFL is dimmed the colour temperature (warmth) stays the same. This is counter to most other light sources (such as the sun or incandescents) where colour gets warmer as the light source gets dimmer  SONY VAIO VGN-FW82JS Battery .
Emotional response testing suggests that people find dim, bluish light sources to be cold or even sinister. This may explain the persistent lack of popularity for CFLs in bedrooms and other settings where a subdued light source is preferred  SONY VAIO VGN-FW82XS Battery .
Some CFLs are labelled not to be run base up, since heat will shorten the ballast's life. Such CFLs are unsuitable for use in pendant lamps and especially unsuitable for recessed light fixtures. CFLs for use in such fixtures are available  SONY VAIO VGN-FW83DS Battery .
Current recommendations for fully enclosed, unventilated light fixtures (such as those recessed into insulated ceilings), are either to use "reflector CFLs" (R-CFL),  cold cathode CFLs or to replace such fixtures with those designed for CFLs. A CFL will thrive in areas that have good airflow, such as in a table lamp  SONY VAIO VGN-FW83JS Battery .
Power quality
The introduction of CFLs may affect power quality appreciably, particularly in large-scale installations. The input stage of a CFL is a rectifier, which presents a non-linear load to the power supply and introduces harmonic distortion on the current drawn from the supply  SONY VAIO VGN-FW83XS Battery .
In such cases, CFLs with low (below 30 percent) total harmonic distortion (THD) and power factors greater than 0.9 should be used.
Infra-red signals
Electronic devices operated by infra-red remote control can interpret the infra-red light emitted by CFLs as a signal, this limits the use of CFLs near televisions, radios, remote controls, or mobile phones   SONY VAIO VGN-FW90NS Battery .
Fluorescent lamps can cause window film to exhibit iridescence. This phenomenon usually occurs at night. The amount of iridescence may vary from almost imperceptible, to very visible and most frequently occurs when the film is constructed using one or more layers of sputtered metal   SONY VAIO VGN-FW90S Battery .
It can however occur in non-reflective films as well. When iridescence does occur in window film, the only way to stop it is to prevent the fluorescent light from illuminating the film.
Use with timers, motion sensors, light sensors, and other electronic controls   SONY VAIO VGN-FW91NS Battery
Some electronic (but not mechanical) timers can interfere with the electronic ballast in CFLs and can shorten their lifespan. Some timers rely on a connection to neutral through the bulb and so pass a tiny current through the bulb, charging the capacitors in the electronic ballast   SONY VAIO VGN-FW91S Battery .
They may not work with a CFL connected, unless an incandescent bulb is also connected. They may also cause the CFL to flash when off. This can also be true for illuminated wall switches and motion sensors. Also, most CFLs will not work with light sensor devices, as in a "dusk to dawn" device   SONY VAIO VGN-FW92DS Battery .
Cold cathode CFLs avoid many of these problems. Timer manufacturers may make products compatible with CFL lamps.
Fire hazard
When the base of the bulb is not made to be flame-retardant, as required in the voluntary standard for CFLs, then the electrical components in the bulb can overheat which poses a fire hazard  SONY VAIO VGN-FW92JS Battery
Outdoor use
CFLs are generally not designed for outdoor use and some will not start in cold weather. CFLs are available with cold-weather ballasts, which may be rated to as low as ?23 °C (?10 °F). Light output drops at low temperatures. Cold cathode CFLs will start and perform in a wide range of temperatures due to their different design  SONY VAIO VGN-FW93DS Battery .
Differences among manufacturers
There are large differences among quality of light, cost, and turn-on time among different manufacturers, even for lamps that appear identical and have the same colour temperature   SONY VAIO VGN-FW93JS Battery .
Lifetime brightness
Fluorescent lamps get dimmer over their lifetime, so what starts out as an adequate luminosity may become inadequate. In one test by the U.S. Department of Energy of "Energy Star" products in 2003–04, one quarter of tested CFLs no longer met their rated output after 40% of their rated service life  SONY VAIO VGN-FW139E/H Battery .
UV emissions
Fluorescent bulbs can damage paintings and textiles which have light-sensitive dyes and pigments. Strong colours will tend to fade on exposure to UV light. Ultraviolet light can also cause polymer degradation with a loss in mechanical strength and yellowing of colourless products  SONY VAIO VGN-FW145E/W Battery .

Efforts to encourage adoption

Due to the potential to reduce electric consumption and pollution, various organizations have encouraged the adoption of CFLs and other efficient lighting  SONY VAIO VGN-FW190EBH Battery .

Efforts range from publicity to encourage awareness, to direct handouts of CFLs to the public. Some electric utilities and local governments have subsidized CFLs or provided them free to customers as a means of reducing electric demand (and so delaying additional investments in generation)  SONY VAIO VGN-FW190EDH Battery .

More controversially, some governments are considering stronger measures to entirely displace incandescents. These measures include taxation, or bans on production of incandescent light bulbs that do not meet energy efficiency requirements  SONY VAIO VGN-FW21E Battery .

In 2008, the European Union approved regulations progressively phasing out incandescent bulbs starting in 2009 and finishing at the end of 2012. By switching to energy saving bulbs, EU citizens will save almost 40 TW·h (almost the electricity consumption of 11 million European households)   SONY VAIO VGN-FW21J Battery ,

leading to a reduction of about 15 million metric tons of CO2 emissions per year.

Australia, Canada, and the United States have also announced plans for nationwide efficiency standards that would constitute an effective ban on most current incandescent bulbs  SONY VAIO VGN-FW21L Battery . 

Venezuela and Cuba have launched massive incandescent light bulbs replacement programs in order to save energy. In the case of Venezuela, the government was able to save 2000 MW of electricity in the first six months of the 2006 program called Mission Energy Revolution  SONY VAIO VGN-FW21M Battery ,

which by 2007 replaced 20 million incandescent light bulbs with CFL from a total of an estimated 55 million light bulbs in the country. Cuba replaced all the 11 million light bulbs used on the island. Also, Venezuela signed an agreement with Vietnam  SONY VAIO VGN-FW21Z Battery ,

one of the large producers of CFLs in the world, to establish a factory to supply the future demand and hand-outs of government light bulbs.

The United States Department of Energy reports that sales of CFLs have dropped between 2007 and 2008, and estimated only 11% of suitable domestic light sockets use CFLs  SONY VAIO VGN-FW25T/B Battery .

In the United States, the Program for the Evaluation and Analysis of Residential Lighting (PEARL) was created to be a watchdog program. PEARL has evaluated the performance and ENERGY STAR compliance of more than 150 models of CFL bulbs  SONY VAIO VGN-FW26T/B Battery .

Labeling programs

In the United States and Canada, the Energy Star program labels compact fluorescent lamps that meet a set of standards for starting time, life expectancy, color, and consistency of performance   SONY VAIO VGN-FW27/B Battery .

The intent of the program is to reduce consumer concerns due to variable quality of products.Those CFLs with a recent Energy Star certification start in less than one second and do not flicker. There is ongoing work in improving the "quality" (color rendering index) of the light  SONY VAIO VGN-FW27/W Battery .

In the United Kingdom a similar program is run by the Energy Saving Trust to identify lighting products that meet energy conservation and performance guidelines  SONY VAIO VGN-FW27T/H Battery .

Fluorescent lamp recycling or Light Bulb recycling is the reclamation of the materials of a spent fluorescent lamp or light bulb for the manufacture of new products. Glass tubing can be turned into new glass articles  SONY VAIO VGN-FW29/B Battery ,

brass and aluminium in end caps can be reused, the internal coating can be reprocessed for use in paint pigments, and the mercury contained in the lamp can be reclaimed and used in new lamps. In the United States, about 620 million fluorescent lamps are discarded annually  SONY VAIO VGN-FW290JRB Battery ;

proper recycling of a lamp prevents emission of mercury into the environment, and is required by most states for commercial facilities. The primary advantage of recycling is diversion of mercury from landfill sites; the actual scrap value of the materials salvaged from a discarded lamp is insufficient to offset the cost of recycling  SONY VAIO VGN-FW290JTB Battery .

Mercury uses

The disposal of phosphor and particularly the toxic mercury in the tubes is an environmental issue. Governmental regulations in many areas require special disposal of fluorescent lamps separate from general and household wastes  SONY VAIO VGN-FW290JTH Battery .

For large commercial or industrial users of fluorescent lights, recycling services are available in many nations, and may be required by regulation. In some areas, recycling is also available to consumers. The need for a recycling infrastructure is an issue with instituting proposed bans of incandescent bulbs  SONY VAIO VGN-FW52JB Battery .

Mercury-free discharge lamps have considerably lower production of visible light, about half; mercury remains an essential component of fluorescent lamps.

Only a few tenths of a milligram of mercury are required to maintain the vapor  SONY VAIO VGN-FW51B/W Battery ,

but lamps must include more mercury to compensate for the part of mercury absorbed by internal parts of the lamp and no longer available to maintain the arc. Manufacturing processes have been improved to reduce the handling of liquid mercury during manufacture and improve accuracy of mercury dosing  SONY VAIO VGN-FW50B Battery .

The amount of mercury in a fluorescent lamp varies from 3 to 46 mg, depending on lamp size and age.  Newer lamps contain less mercury and the 3–4 mg versions are sold as low-mercury types. A typical 2006-era 4 ft (122 cm) T-12 fluorescent lamp (i.e., F32T12) contains about 12 milligrams of mercury  SONY VAIO VGN-FW47GYH Battery .

In early 2007, the National Electrical Manufacturers Association in the US announced that "Under the voluntary commitment, effective April 15, 2007, participating manufacturers will cap the total mercury content in CFLs under 25 watts at 5 milligrams (mg) per unit   SONY VAIO VGN-FW465GJB Battery .

CFLs that use 25 to 40 watts of electricity will have total mercury content capped at 6 mg per unit."

A broken fluorescent tube will release its mercury content. Safe cleanup of broken fluorescent bulbs differs from cleanup of conventional broken glass or incandescent bulbs  SONY VAIO VGN-FW465GJ/BE1 Battery .

99% of the mercury is typically contained in the phosphor, especially on lamps that are near their end of life.


Lamps made up to the 1940s used toxic beryllium compounds, which were implicated in the deaths of factory workers.However, it is very unlikely that one would encounter any such lamps  SONY VAIO VGN-FW465J/B Battery .

Formerly, toxic materials such as beryllium, arsenic, cadmium, and thallium were used in phosphor manufacture. Modern halophosphate phosphors resemble the chemistry of tooth enamel. The rare-earth doped phosphors are not known to be harmfulSONY VAIO VGN-FW45TJB Battery .

Mercury containment

When discarding a fluorescent tube, the main concern is the mercury, which is an important pollutant. One way to avoid releasing mercury into the environment is to combine it with sulfur to formmercury sulfide, which is insoluble in water  SONY VAIO VGN-FW45GJB Battery .

One advantage of sulfur is its low cost. The reaction is shown with the equation:

Hg + S ? HgS

The easiest way to combine sulfur and mercury is to cover a group of fluorescent tubes with sulfur dust and break them SONY VAIO VGN-FWZJ/H Battery ;

when the glass is put into a bag to continue with the reaction, the mercury will combine with sulfur without any other action. The glass can be recycled where an appropriate facility exists. A quantity of 25 kg of dust sulfur is enough for 1000 tubes  SONY VAIO VGN-FW41M/H Battery .

Disposal methods

Spent fluorescent lamps are typically packaged prior to transport to a recycling facility in one of three ways: boxed for bulk pickup, using a prepaid lamp recycling box, or crushed for pickup  SONY VAIO VGN-FW41J/H Battery .

Afluorescent lamp crusher can attach directly to a disposal drum and contain dust and mercury vapor.  Disposal methods are regulated at both the state and federal level. Proper recycling of fluorescent lamps can reduce human mercury exposure SONY VAIO VGN-FW41E/H Battery .

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