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The Truth About Flourescent Lights? 97

Posted by Cliff from the why-does-the-flickering-hurt-so-much? dept.
plato is desperate for answers to the following questions: "Help! I, for one, am driven insane (eg., headaches) by the flickering and buzzing of flourescent lights; I know others are plagued by the same problem and am looking for some answers. At what refresh rate do flourescent lights flicker? Why does flickering (eg., flourescent lights, computer monitors with bad refresh rates, strobe lights) cause headaches for some people? What are some better alternatives to flourescent lights for an office environment? How cost effective are they (in the short- and long-term) compared to natural light, (which isn't always an option)."
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The Truth About Flourescent Lights? More

The Truth About Flourescent Lights?

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  • Try the EMF-L archives. (Score:1)

    by Anonymous Coward
    You might find good info in the searchable EMF-L archives. If you don't, then you can always send a message with your inquiry to the list moderator Roy Beavers (rbeavers@llion.org). Good luck!

  • Get some FAQ on Fluo lighting (Score:1)

    by Anonymous Coward

    Get it right here:

    Fluorescent Lamps, etc... Faq [misty.com]

    Lots of other interesting info there too. Like Arc Lamps, etc... );-)

  • Flickering (Score:1)

    by Anonymous Coward
    North America uses 60hz electric power, so I'd guess the lights flicker at 60hz. I think 72hz is the minimum recommended refresh rate, anything lower can cause eyestrain. Not everyone can see flickering (lights or monitors), but looking at it long enough would probably give them a headache.

    I've noticed that some fluorescent lights seem to flicker less than others (ie. I never notice flicker at school, but the fluorescent lights in my basement drive me crazy). Do different types of lights flicker at different rates? (maybe some light bulbs have coatings that hold the light energy for longer than others?)

  • Inaccurate color (Score:1)

    by Anonymous Coward
    As a photographer I have examined the spectral output charts for florescent lights, and there is an overall green cast with many spectral regions totally missing (meaning certain colors don't show up), and others exaggerated. In contrast, tungsten lights have a mathematically continuous spectral output (tending toward orange, around 3200 Kelvin). Daylight is also continuous (and bluish, around 5500 Kelvin).

    Because of this ugly green color cast, and the flicker, I don't use florescent lights in my house for esthetic reasons.

  • If you are senitive to florecent lighting (Score:1)

    by Anonymous Coward
    here [natralitefilters.com] is a place that sells filters that make the light more confortable, they even sell glasses.
  • In America 60 Hz AC is used, but because it is a sinusoidal function, the tube should light twice every period (once with the current flowing forward and once flowing backward).

    Maybe it's possible to buy fluorescent lights with phosphors that glow longer (do they use phosphor in a TL?).

    It's also important to notice that some LCD's refresh at almost the same frequency as lighting, which causes _very_ annoying flickering (due to interferention between the light and the LCD refresh).

    Although I'm an EE student, I'm not really an expert on this, so don't sue me on this info :)
  • Hey - it's what I do. When I'm coding, I usually turn down all of the lights most of the way - I find it improves the contrast on my old monitors.
    I also hate direct light when I'm really deep into a project.
    I stick 2 desk lamps in corners of the room, and aim them up.
  • A slow diode would make the light look smoother, not rougher (ie make it seem like the phosphors last longer).
  • I don't think 'holographic' is quite the correct word but I've heard about this too. It's in use is various forms around many office buildings and home I've seen. Frank Lloyd Wright even built something similar to this into a building of his (though I can't remember the name off the top of my head) quite a long time ago. It does give a very natural light but the fibers are really expensive, too much so for most office buildings since most workers have no problem with floresent (sp?) lights.
  • I saw something on TV (I think it was on Nova)
    about this. It seems that they have done tests
    and when they asked people to read with floresent
    lights the eyes moved in a much more jerkey fashion. On the other hand when they switched to a
    light that flashed at 20Khz they normal smooth motion returned.

    I'm just thankfull that I have abig window and can
    mostly leave the overhead lights off here.

  • While I really prefer not having any fluorescent light at all (and am lucky enough to not have any now, but haven't always been) they are much more bearable if you have the kind that point upwards at the ceiling with an opaque bottom cover, rather than the typical translucent plastic cover that lets them shine directly down. It's still ugly compared to sunlight, halogen, or good old fashioned incandescent bulbs, but you do avoid the strobing effect.

    That probably doesn't help, unless you happen to be designing the lighting for your building. But it's something to look for if you do have a choice in the matter.
  • The one true illumination source. Just enough ambient light to see the keyboard, nothing more. Perfect for coding when roommates want to sleep. (If only mine didn't shift colors from blue to orange...)
  • 1) someone moderate this guy +2 for bringing up something I was just thinking about.
    2) If you've been to the doctor and had a stress EEG to help diagnose migraine, did they make you close your eyes and put a strobelight over your face? Hmmm... see, I'm a migraine sufferer, my sister is a migraine sufferer, and I know several other migraine sufferers, and most of us believe that flickering lights or lights that are outputting more light in the green-violet spectrum are triggers for migraines. Also, a lot of us absolutely hate prolonged exposure to Blacklights, especially the fluorescent ones, so our theory is that ultraviolet is a trigger (goes with the other fluorescent lights too). Basically, we suggest to other people experiencing bad effects that they go to incandescent or halogen lamps, try to go with natural spectrum bulbs, try to work somewhere with windows (no not the MS kind) so you can have natural light (unless you're a vampire) and definately run the monitor/video card at a setting you can tolerate. Also remember that if you are diagnosed as having migraines and you can document such things as triggers, that according to various legislation (the Americans with Disabilities Act for one) that your employer must attempt to make a reasonable accomodation for you. So they should be able to pay $50 for a decent lamp and bulb, or $250 for that 3dfx Voodoo 3 3500 TV :P
  • Solatube [solatube.com] sells a tubular skylight that basically acts as a "light pipe" from the roof into the ceiling of any room in your house. I have no idea how well they work, I've never seen one in real life, I just remember seeing an ad in the back of Discover magazine and thinking it was probably not a bad idea.
  • Hey how fast does that transister respond? :-)

    It's probably fast enough, but ya never know, right?
  • We had a problem with having no light during the day in the bathroom and kitchen. Saw a demo of Solatube's at one of those home shows. Went into a totally black room... shut the door, then pulled a lever, it opened the panel what was covering the tube, was like sitting outside, very good. The other attraction about these is that they don't add a lot of heat to the room. You can also get nifty fan attachments for toilets and suchlike. ---

  • If you like halogen light, but are concerned about the power consumption or the heat, Sylvania (tm) makes a bulb that goes in a normal incandescent socket but is a halogen bulb. It looks mostly like an incandescent, but the glass is much thicker. I love this bulb for a few reasons:

    • It -doesn't- get super hot. It's no hotter than an incandescent.
    • It's brighter than an incandescent.
    • It replaces incandescents in the same socket.
    • It's only about $3.00 (US) at your local Home Depot (tm).
    • It's only 100 W.. a lot better than those ordinary halogens.

    No, I don't work for Sylvania. :) I just wanted to share the wealth gleened from my quest for acceptable lighting.



    Zeitgeist
  • (Note... this deals more with the 24fps comment than being on-topic).

    The difference between 12 and 24 is fps is QUITE obvious to the casual observer, 24 to 30 is very obvious to somebody watching on a big screen (I'm talking movies), and you have to go to 60 fps before pans (moving the camera sideways) look realistic.

    Star Wars:TPM had lots of pans that left me naseated. On a TV screen, you can get away with it -- on a IMAX screen, you just don't do pans. Period. It leaves the audiance seasick as their visual cortex tries to reconcile the "jumping" images.

    I'm not all that heavy into cinema, but I'm involved in a Japanese animation club, and I am heavily involved in Rocky Horror, which has occasionally lead me down the path of NTSC vs. PAL, differing aspect ratios, screen media (the actual sheet that is projected upon), and animation rates. I also live right near an IMAX theater that shows nifty space related films, so I've *seen* the difference between various frames per second.

    --
    Evan

  • It's hard to tell. I've heard tell that seasonal affective disorder, which is basically depression linked to shorter daylight hours in the winter, can be treated by daily exposure to high-intensity banks of flourescent lights. But my understanding is fuzzy, and the lights may have been carefully selected for a spectrum that differs from ordinary flourescent tubes. (Incandescent or halogen bulbs could do the same, but may be less safe due to the heat produced - I don't know.)
  • As a College student I live in dorms that have 2 Flourescent lights per room and a window, that's all the lighting they provide. And I spend all day in classes that have flourescent lights. And I have noticed that I've been getting headaches more often since I came back to this. My alternative is just putting a lot of lamps arroud my room. In my small space of the room (11' x 6'), I have 3 lamps that I use. I find that I actually have fewer problems with the two Flourescent lights when they are on if I have these lamps on as well. I personally think Halogen lamps are a better solution that flourescent, but they get very hot and can cost more. (I've never really done a close comparison to cost).
  • Actually they flicker at approximately 120hz because the voltage waveform peaks (+ & -) at 120hz (60hz for + voltage and 60hz for - voltage). Also power is what really matters and + and - voltage make no difference, power peaks at 120hz.

    -Aaron
  • Try adding some X-mas tree lights to the mix. They really add a nice effect in a room, especially if you use solid color lights. Just pin them up near the ceiling.
  • Why do 99% of fluorescent light fixtures use those hideous cool white tubes?


    There are better fluorescent phosphors, but most buildings and offices use cool white.

  • Neither, try fluorescent.
  • And here's the link. Look for Tegenfeldts posts. They are the most informative (albeit a bit too techy for some).

    http://www.wave-guide.org/archives/emf-l/
  • One of the things we do here (a computer science deartment, so we have lots of monitors and everything is flourescent lighting) is have office lights arranged on two circuits. There are two standard 4-bulb fixtures in the ceiling; two bulbs per fixture are on one circuit (with one switch) and the others are on another circuit(with a second, independent switch). The the circuits are out of phase with eachother, so one peaks during the other's trough.

    Now, my office has a window, and my offcemate and I each have new, large monitors driven at 72Hz+ refresh rates ... so I'm probably not in a position to be the best judge of how well this works. I'll just say that if this didn't at least once have a benifit, I doubt they would hve gone to the trouble to arrange this in every office.
  • That's right. I have two flo. bulbs right above my head. Once I remove them, everything is brighter and easier to see (especially Quake, try it). I'm probably going to get a desk lamp next to help when I'm doing paper-type work. I still have some light from the bulbs on the other side of the room, but less light certainly rocks.

    Monty

  • Flourescent lights refresh at 60htz, really, really old monitors run 56 or 60.
  • The light does not go dark when no power runs through it. Flourescent lights work on the principal of a powder(mercury based I think), on the inside of the tube being excited to a higher energy state, then releasing that energy over a brief period of time at a lower wavelength than it was absorbed at. I am fairly sure(not completely), that this relaxation time, is longer than the power oscillation period(1/120 seconds).
    So all this means that while the light does flicker, it is never completely dark. Sorry to split hairs, but us physicists, have to keep the engineers in check :-)
  • BTW, you get florescent lights..mainly used in portable lamp things which run on DC (battery) power. Only problem is that theyre compact since theyre used in small portable stuff.
  • There is mercury inside the tube, in a gaseous state (it "evaporates" from a little droplet of mercury in the tube. The gaseous mercury atoms become excited by the electric current running through the tube, and the photon they release is in the UV spectrum. The UV photon hits the phosphor coating on the tube, and that coating glows with the light you actually see. Sodium vapor lamps (the orange ones you sometimes see as highway street lights) use a similar principle, but the photon is orange, so a coating on the bulb is not required.
  • The "HF" types of fluorescents he speaks of are indeed superior to 'regular' fluorescent types... I use them on my boat, primarily because of the dimming capability. The smoother light output is a great improvement over other inexpensive types.

    However, these types of fluoro's are very expensive and are often very hard to locate... Besides the OEM, I had to find a specialty lighting store to find anyone who knew of the lights I was looking for...

  • I've been reading some of the comments here, and I wanted to share some things I know about flourescent lights.

    Flourescent lights are not supposed to buzz, hum or flicker. If you have a noisy or flickering light, the bulbs may be starting to wear out, and will need to be replaced. Other common causes are a bad starter (for a starter-type light), loose wiring, a bad connection between the bulb and lamp holder, or the balast is going bad. Also, a bad ground can cause any number of problems.

    As another poster mentioned, older flourlescent lamps used a magnetic balast ( esscently a transformor) while newer ones use an electronic balast (usially a switching power supply with some extra circuitry). If the fixtures in your office are more than a few years old, it may be a good idea to replace them.

  • Uh, isn't there still the issue of slow flicker rate with candles too??
  • I use a slumber-bulb in a lamp the other side of the room (about 4m) behind me. It gives me enough light to stop me falling over things, but doesn't interfere with my work. If I need to see properly around my desk, I have a halogen light to my right on a shelf, angled at the corner - this creates a nice ambient glow without blinding me.
  • Low frequency stimulus (of any sort) interacts with natural brain waves, and can upset the balance. This is why flickering bugs us so much. IIRC brain waves range in frequency from about .5 Hz to about 20 - 30Hz.

    I used to program laser shows, and I know that we had to be VERY careful about not flickering at the same rate for too long. People have actually been driven into seizures from exposure to low frequency flashing lights.

    Another thing to keep in mind is the 'beat frequency' of two unrelated sources. For example, a 60 Hz light fixture and a 59.7 hertz monitor (most monitors are slightly off frequency, while the power line is always dead on), produce a .3 hertz beat frequency. That slow pulsing is real bummner.

    Things don't get much better as you go up in rate. At 72 Hz, you get a 12 Hz beat, which is right in the middle of the range of brain wave activity.

    That's what drove me,

    Loopy :)
  • Since so many people in work environments complain about florescent lighting, there must be some kind of "anti-florescent movement" web site (or pro-halogen site) -- can anybody think of one?
  • Even if the electrical engineers among us claim that they flicker at 120Hz, I find this hard to believe. I find the flicker on florescent lighting to be about as bad as the flicker on 60-70 Hz monitors (which is _very_ perceptible to me -- that's why I've got a refresh rate of 100Hz on my monitor @ home). With computer monitors, I stop noticing flickering @ 80Hz, and I can _definitely_ see florescents refreshing, so it's got to be 60.
  • Why, chemically/biologically, do flickering things (strobe lights, monitors/florescent bulbs with refresh rates of less than 70-80 Hz) cause headaches, migranes, and general annoyance? Does the eye have some kind of sensitivity to such changes?
  • I suppose I could look it up -- but is it florescent or flourescent (or are they both acceptable, with the "u" being an anglophilic spelling)?
  • Electronically controlled units use higher frequencies, overcome the headache problems, and use less energy per unit of visible light output. They are common in Europe where energy is more expensive.
  • Excuse the typos, if there are any when I'm done. I do much better when I'm paid for my writing. There are two types of "flickering" in flourescent lights. One can be much lower than 60 hz, and I've seen it cycle through this from just a few (2-5) times per second to once every two or more seconds when the bulb is really on its way out. It sort of pulsates near the end(s) of the bulb in the discolored portion, and you can see the light seem to "travel" outward or inward. Replacing the pair of bulbs fixes this problem, unless the real problem is in the ballast transformer. The other one is strobe-like in nature, much faster than the eye can detect, but if you have a rotating disc of the type you used to use on a record player turntable or lookl at a fan at certain speeds, you will see the effect. Some people claim to get headaches from these types of lights. Could it be something other than the fast switching at 120 hz, like the greenish light? You might try some full-spectrum bulbs and see if that helps. It is supposed to help some people with depression as compared to standard flourescent bulbs. BTW, there is no rectification going on in the bulb, but the reason for the 120 switching is similar to what happens in full-wave rectifiers before the pulses are buffered by power regulation (capacitors, inductors, Zener diodes, etc. T2000
  • Is it not possible to use floresent lights with a DC power source. If this was true, then there would be no or verry little flicker. All you would need is an in-expensive AC/DC bridge and possibaly a transformer. It is relatively easy and efficient to convert AC to DC. Could it be as easy as installing a module in each room to do this?
  • I've seen it mentioned in several places (memory fails me - maybe New Scientist or Scientific America). Seems that at about 100Hz the flicker interfers with the eyes ablity to detect edges (or something like that).

    I find that 75Hz gives me a headache (on a 19 inch) but 85Hz is just fine.

    I hadn't noticed any problems with 100Hz but after reading thoes reports I've stuck to 85Hz for all resolutions.

    Back to topic: I also get headaches from flourescent lights, but I know very little about them. I wouldn't live some where that had them, but I have little choice at work.

  • Arrangement of the office can have wonderful effects besides increasing window light. It can really liven up a person at work.

    This sounds like a quote right out of a guide to Feng Shui [mistral.co.uk].
    Who would have suspected that Confucius knew about fluorescent lights?
    --

  • In most people, its a real small degree. But that goddamn flickering ends up fucking with the firing of neurons, even on normal people. Hence annoying.

    Anonymous Coward, get it? :)
  • ...many monitors support up to 200hz at certain resolutions. Doesn't mean they do them all that well ;) I like to play with new monitors and figure out the 'optimum' refresh for each resolution. Thankfully I have a g400 to help me do so.

    Anonymous Coward, get it? :)
  • Rectifying current is a nonlinear operation, so it introduces harmonics. If you know how to calculate Fourier series, compare the (single) component of Sin[60 Hz * t ] with the spectrum of Abs[ Sin[60 Hz * t ]. You will find the strongest component at 120Hz, and NO component at 60Hz.

    The flicker, by my hypothesis, is due to incomplete rectification, which would allow some 60Hz component to sneak through. For example look at the spectrum of the slightly perturbed problem Abs[ d + Sin[60 Hz * t] ], where "d" is some small DC offset. The bigger the offset (i.e. the more shoddy the rectification) the bigger the 60Hz component.

    This could explain why older and cheaper lights begin to flicker, since their rectifying components may be poorly made and deteriorating.

  • I understand that it may also have something to do with genetics. When my mother was in college, she started getting the flourecent-lighting-induced headaches that so many posting on this have complained of, and her doctor reccomended to her that she get glasses with photogrey lenses, and that it was pretty common among blonde-haired, blue-eyed types. She said that pretty much cured her. Incidentally, she told me this when I started moaning to her about the quality of my monitor (ah, the joys of being in college. "Mom, can I have more money?"), which can go no higher than 60 Hz. I swear, the screen absolutely twitches. Oh well, maybe next semester...
  • 3M makes a product that is like a thin layer of film inside a tube that you put a light at one end and it illuminates the whole length of the tube. I saw a demo a couple of years ago, I don't know if they make them in cubicle-lighting size, though. The one I saw was pretty big. Try their website [mmm.com] and search on 'light pipe' Another big minus for flourescents is the disposal. The Knucklehead I bought my house from had the living room decked out with a drop ceiling, aluminum foil on the actual ceiling, and no less than 20 48" tubes. Buzzed like a swarm of locusts. Add the 12 fixtures in the basement, the stockpile of burned out bulbs, and I'm sitting on like 2 pounds of Hg, and they cost money [dakota.mn.us] to get rid of!
  • ... with Flourescent lights is when I am also at a computer screen, and haven't given my eyes a rest at all in the last four or five hours. I do not get a headache, however, I simply get dizzy, and feel like I'm falling out of my chair. After that passes, I will generally get up and walk about some, and then I'm good to go for another short session.

    This doesn't seem to happen if I do not have flourescent lights on and am at the terminal, or if I am doing something else in a room with flourescent lights. 'Tis only the two in combination.

    Cheers!
  • HAOLOGEN = ALMOST SUNLIGHT Actually I have SAD and it is not flourescent exposure but warm, full spectrum exposure that helps. I use halogens, which are about the best you can get outside of natural sunlight, and frankly they are comparable in initial costs to flourescents, both fixture and lamp wise. However, they are big electricity suckers, so if you pay your electric bill (I don't I am college student) or if you believe that reducing electricty consumption will help the environment, then go for the more full spectrum flourescents, as others in this reply sequence have suggested, those with better phosphors. -there will always be women in rubber flirting with me -RENT
  • As far as monitor refresh rates, everybody seems to be saying "go as high as you can" (in vertical refresh rate)... I experience the same between 60 and a little over 85hz, but at a little over 100hz, I feel more uncomfortable with the screen image. Assuming that my hardware is all working correctly (as far as I know everything is completely capable), am I crazy?

  • Add incandescant lighting!!! (Score:2)

    by Anonymous Coward
    There was a show on TV awhile back that said that the eye can detect up to several thousand hertz (this can be seen by monitoring the optic nerve), although there is no "flicker" apparent above 30 hertz or so, and that faster is always better. I recall it took 500 or 600 Hz to control the objectionable eye strains and something like 4000 Hz to eleminate them altogether.

    The yellowish mercury free (iron-iodine) lights they are putting in everywhere have an extreme effect on me personally--I really wanted to scream when they took out the old bulbs and put in the new ones (I've been through this at two universities--they could save enough in two years to pay for hiring the electricians to do the switch, plus no hazardous waste mercury bulbs to dispose of from time to time). Others apparently find them less outrageously painful.

    I have evolved two solutions:
    1. A flourescent desklamp with a natural spectrum bulb. Bulbs from WallMart, about $5. There used to be "office rated" lights with no 60 cycle transformer hum, but now everything is from Taiwan and hums after it gets warm. About $65 versus $95+ for the Swedish ones that don't hum, if you can evern find them (I haven't seen one in years.) The desklamp plus a little natural light will work wonders.
    2. A substantial desklamp using either an incandescant bulb (100W) or (best) a really good halogen lamp (50W,about $50, although sometimes on "clearance" for $30 or so). Get the one with the counterbalance, length adjustments on the arms, and 2 intensity levels if you can.

    The economics are such that you will never see the really good flourescent illumination again. The mercury free Trimline (tm) bulbs with their reduced power coonsumption will be the choice of building managers for the indefinite future. You have different things going on inside the bulb, and different phosphors, and much lower intensity (the human eye is more sensitive to yellow light, so less light intensity appears bright nonetheless). The old office had 4 or 5 times the illumination level, and the higher powered bulbs seemed to give a more constant illumination--maybe they didn't cool off completely in the ionized core, or somehting. Anyway, those days are gone forever.
  • That flickering you're seeing is not the flickering of the light or the display; it's the interaction of the two. The human eye can detect flickering at a maximuim of somewhere between 12 and 24 Hz (can't remember which one, I think it's 12) due to persistence of vision (this is how animation/movies work; film updates at around 24fps from memory). If the refresh rate of the display is close enough to the flicker rate of the lights, you will then get flicker due to the beat frequency which is abs(f1 - f2). I believe harmonics can come into this as well (they do, but it's the exetent to which they affect things that I reffering to). Solution: either adjust your refresh rate or turn off the lights. BTW, this is explained in the display timings faq in XFree86 (written by ESR). Sorry, no link.
  • They don't use anything cool like fiber optics, though. ;)

    Curiously, though, do you have any idea how much these Solatubes cost? I can't find anything resembling a price on their web site...
  • "Holographic" was the word used in the article I read. I don't remember the specifics (that's kinda why I was asking), but the light was either piped against or through the back of some holographic film, presumably to get an even, full and rich distribution of the light. I wish I could find a link to that...
  • At work, one of the office workers had to go home because of epileptic seizures possibly induced by the flourescent lights. I changed out both the ballasts and the bulbs and have not heard of any problems since.

    There might be other ways to reduce the annoyance of 60Hz flicker, such as angling the desk and reflective framed pictures on the wall, or even placing large plants around the desk. Arrangement of the office can have wonderful effects besides increasing window light. It can really liven up a person at work.
  • I took part in a series of psych studies where they were measuring the rate at which your brain processes information and relating this to IQ. The good news is that they found a direct correlation. There were a lot of different tests, but one that's relevant used a flickering light controlled by computer and you had to say if it was constant or flickering. Over a series of tests they determined the fastest speed at which your brain perceived the light to be flickering.

    There's no thinking involved as such in this kind of test: either you see the light flickering or you don't. The bad news is that people of the highest IQ (measured by 6 different kinds of test - it took days!!) could detect flickering down to 16 milliseconds (IQ of 130-140) which is about 62Hz. Lowest IQs tested (90-100) were down around 30ms. The relationship was *roughly* linear.

    Hence, next time you're in a room and you're the only one complaining about flickering lights or screens, you might just have to console yourself with the thought that you're the brightest person in the room!

    Personally, I had the fastest flicker rate (16ms), I notice flickering lights and screens if I think about it, but don't seem to be adversely affected by fluro lights. Maybe I'm just used to it (my original PC ran at 1024x768 *interlaced* ugg!! I used to think it was horrible to stare at, but strangely, after a few weeks I didn't notice any flicker at all). I'm sure other factors are also involved. (similar to the story of the guy with the upside down glasses, but that's a major digression :-)

    By the way, I much, much prefer the new "daylight" fluro tubes you can get, which have a much more natural spectral distribution, making other fluros look yellow or brown by comparison.
  • If you don't like the fluorescent lights in your house, try different bulbs. The bulbs may be getting old or may have been whatever random type was cheapest at the hardware store. Look at a hardware or lighting store for different kinds of bulbs.

    There are phosphors which glow longer, there are ones which produce a different spectrum (combination of colors).

    Or, if it's your house, change the light fixture. Start by replacing the "starter" in case a bad one is interfering with the bulb's power. There are also different power circuits available for various bulbs. Or you can change from fluorescent to the various low-energy vapor bulbs. Or put in a track light or X-10 controllers so you can adjust the lighting in different ways to suit the situation...such as giving some chairs spotlights for reading, or turning lights off when watching a movie.

  • You can run flourescent lamps off DC current. The problem is, you generally need to convert it into AC to be able to efficiently raise the voltage.

    Plus, an inductor is good for regulating the current flow to the bulb.

    Compact and other flourescent tubes that run on DC usually use a high frequency oscillator and a small transformer to get the high voltage. With high frequency, you can use a much smaller (physically) transformer and retain the same efficiency. }:)

  • I prefer incandescent, of course. I make sure that the shade performs its function well (doesn't shine direct light into your eyes). I place it somewhere behind the front of the monitor (right now, to the left, on top of my subwoofer).

    In an office environment, you may have trouble getting this unless a doctor recommends it.

    Ideally, you have your own office (I hate cubicles, but that's a given) that you can simply turn off the flourescent light in.

    Oh yeah, flourescents give off *lots* of noise. You can demonstrate that with a microphone. That may be another "playing card" you can use with your employer.
  • There are a lot of popular misconceptions about fluorescent lighting, and I see a lot expressed here.

    Good quality modern fluorescent lights that are operating properly don't have a perceivable flicker. Easy to prove: Hold a stick (pen, pencil ruler) up in front of you while looking at the light. Hold it by the end and shake it back and forth rapidly in an arc. You should see a smooth blur. Do the same thing in front of your monitor. You'll see a strobe effect, several apparently stationary images of the stick or whatever.

    (Do this in front of a TV (in the US, NTSC type) and you'll see a curved image of the stick.)

    The reason they don't flicker is the same reason you can still see the image at the top of a monitor when the electron beam is scanning the bottom of it - persistence. The phosphor that gives off the light continues to glow after the electrons stop hitting it.

    Different phosphors have different persistence, which is a good thing. If you had a long-persistence phosphor on your TV screen you would get trailing images when objects moved rapidly.

    Phosphors used in lighting today have fairly long persistence. You may be able to detect the variation using something like a strobe wheel (spinner with lines spaced at regular intervals, often used or found on record turntables), but you shouldn't be able to see it in normal circumstances.

    The "flicker" rate is 2x the rate of your AC current - 60hz in the US, 50hz in some other countries. Because the current has a peak voltage in each "direction" once per cycle, you get two peaks and two "troughs" in one cycle, so the correct rate for the US would be 120hz.

    Aircraft and some military installations, along with some unusual building installations, use 400hz AC power, which would yield 800 "flickers" per second.

    Different phosphors also give off different colors. Depending on what you want to light, you can choose the color. Grocery meat counters are often cited as a place where a warmer, redder light makes the product look better. Graphic design studios would want a more even color for accurate perception of what they are working with.

    The pinkish high-pressure sodium vapor lamps actually have a pretty neutral color, unlike the older mercury vapor designs, which are blue to green. Many people didn't like the new style at first because it seemed so pink next to the mercury.

    LOW-pressure sodium lamps are monochromatic yellow. They were cheap, they didn't attract as many bugs at night, but you often could not tell the color of a car under them.

    If you're getting headaches at work, it's not because you're under fluorescent light. It's most likely that the lighting isn't appropriate to the work you're doing (or there's some other factor like your monitor).

    It COULD be because you're under BAD florescent light. Fixtures need to be cleaned, bulbs need to be replaced, and so do ballasts on a regular basis. A fluorescent lamp can loose fifty percent of it's light output before it finally quits. More than sixty percent of the possible output is often lost to dirt on the lamp and fixture.

    Cheap fluorescent lamps might not have good phosphors in them, giving bad color and possible 120hz flicker.

    Bad ballasts CAN induce a noticeable flicker. They're noisy, and noise causes fatigue, and they're dangerous - they can catch fire and even explode.


    One reason STROBE lights or lights without phosphor can cause people problems is that there are natural brain wave patterns that will try to synchronize with the frequency of the strobe. One of these is slightly below 60hz, and early research on Attention Deficit Disorder (ADD) thought that fluorescent lights were speeding this up and causing the hyperactivity of the kids. (For the reasons above, this theory was discarded.)


    So if you're getting headaches at work, don't bitch about it being from fluorescent lamps. If the lamps flicker, try to get them serviced. If the ballast gets noisy, it's going to go out soon and needs to be replaced. Report it. Look at other factors such as glare, too much or too little light, bad positioning of your monitor, poor monitor quality, and for those of us over 40, failing near vision. A good rule for the lighting level around your monitor is that objects you see around it should have about the same light level. A black screen with white or other bright colored text against a well-lit bright background will cause problems, as will a white screen with some dark text against a dark or window.
  • An article in today's Guardian [theguardian.co.uk] talks about a new LED they've made from Gallium Nitride. It uses eighty percent less power than a conventional light bulb, plus it will last for 100,000 hours compared to 1,000 for normal. This is a quote from the column:

    "In principle all these fluorescent tubes, so long and ugly, you could replace with these tiny light emitting diodes in any shape you want. The actual LED is a fraction of a millimetre across."

    The output of these devices is equal to that of a conventional tungsten filament bulb.


    No matter what it looks like, there isn't a .sig here.
  • I've measured it [jlab.org], and it goes so close to dark the difference isn't worth talking about. The phosphors are clearly very short lived (less than a millisecond). The trace from a photodiode looks like abs(sin(x)).
  • FULL SPECTRUM is the way to go. There are full spectrum incandescent bulbs (have to look for them) and full spectrum fluorescents as cheap as $7 per bulb at Home Depot and I think I saw them at Wall Mart too. I use both.

  • Holographic lighting? (Score:3)

    by Fastolfe ( 1470 ) on Monday September 13, 1999 @09:19AM (#1687307)
    While not strictly relevant, I've read in the past of efforts to collect sunlight at the tops of buildings, pipe this light down to individual rooms using fiber-optics, and re-distribute it with holographic panels. In theory, the result would be pure sunlight radiated in a very natural pattern, much like a natural skylight.

    Has anybody heard of any applications of this idea?

  • Made worse by low refresh rate on monitor... (Score:3)

    by Spectre ( 1685 ) on Monday September 13, 1999 @01:03AM (#1687308)
    I worked in a cube farm in a room that had been converted from a training/meeting room. The primary lighting was fluorescent. When the fluorescent lighting was the only light source, people startd developing headaches.

    Interestingly enough, the people who were screaming in pain were those with 56 or 60 hz refresh rates on the monitors. Replacing the monitors with newer models capable of 72 hz or higher refresh rates eased the problem to tolerable levels.

    We solved the problem by using the secondary light system as much as possible (low wattage incandescent floodlights). Management didn't like the "mood lighting" though and would turn on the fuorescents whenever they wandered by.

    Eventually we used the ADA (only applies if you are in the US, but I'm sure many countries have similar legislation) to force the fluorescents off (one member of the group had chronic migraines triggered by harsh lighting, especially flickering). It's amazing what you can get declared "reasonable measures" to meet the needs of a "disabled" worker! The ADA is your friend!

  • A much simpler solution... (Score:3)

    by ElJefe ( 41718 ) on Sunday September 12, 1999 @06:00PM (#1687309)
    Real geeks code in the dark :)

    -ElJefe

  • Full-Spectrum Fluorescent Lights (Score:3)

    by ctlmb ( 90874 ) on Monday September 13, 1999 @02:42AM (#1687310)
    Because the lighting is so important for my reeftanks and freshwater plant tanks, I've learned a lot about different types of lighting. One thing that these tanks absolutely need is full-spectrum lighting. In contrast to the el cheapo cool-white fluorescent lamps which emphasize one or a few parts of the light spectrum, full-spectrum lighting provides light over the full color spectrum. This results in a more natural, less harsh light. The full-spectrum light that's widely available in a variety of sizes is the GE Chroma50. I spec it for every new office I move into. I don't know if this will help with the flickering problem, but at least the light quality will be better.

  • three fold problem (Score:5)

    by Anonymous Coward on Monday September 13, 1999 @03:40AM (#1687311)
    I've studied this a lot, without the help of my employeers, I might add.Turns out there are three problems. The flicker rate of the florescent (magnetic ballast, 60 Hz in USA), the refresh rate of your monitor, and glare.

    You may be able to replace the existing florescents with compact florescents (electronic ballast). They often use a higher flicker rate, and they use long persistance phosphers that glow longer and reduce flicker (remember the original IBM PC's green monitor - had long persistence phosphers also). Yes, you can get electronic ballasts for standard fixtures that take 48 inch tubes.

    Indirect lighting is almost always better for computer users. I usually use a halogen up-light (six foot tall "torch" that points at the ceiling). Reduces glare, and reduces flicker (any light source based on a hot filament has minimal flicker since the filament tends to stay at a pretty constant temperature).

    The best, of course, is north facing windows. Excellent light quality (perfect color temperature, zero flicker), and no glare. Damn few archictects know or care about this (Frank Lloyd Wright taught us this in the 1910s or so), sadly. Shame on the jerks that design "modern" office buildings!

    Obviously, you should have the best monitor you can get, running at the highest refresh rate your video card can use with the resolution you need. I'm running 1280x1024x24 @85Hz on a 21 inch monitor.

    A forth overlooked problem is that of seating position, but that's not the subject here...

  • Re:Indirect fluorescent (Score:5)

    by choco ( 36913 ) on Sunday September 12, 1999 @07:47PM (#1687312) Homepage
    I am posting from the UK so some of my terminology may need "translating" for the US Market.

    Ordinary, Low Frequency (LF) Fluorescent likes do have noticable flicker which can certainly upset some (many?) people.

    There are many ways of reducing the problem

    1) In large installations the lighting should be wired such that each area is lit by lights on all three phases. This reduces the perceived flicker.

    2) Where three phase power is not available you can buy "lead/lag" fittings with two tubes wired such that the flicker in each tube is out of phase. These are only available in small sizes and are hard to get.

    3) The unpleasant effects do seem to be reduced if the you can bounce the light(s) off another surface

    4) But the best solution is to use "High Frequency" Ballasts and tubes. This converts the incoming supply to DC and then uses a high frequency inverter to run the tubes. They offer lower weight and better efficiency than LF Fluorescents. The persistence of the phosphors in the tubes means that there is virtually no flicker present at any frequency.

    HF fluorescents have a higher capital cost than LF fittings - but the difference has become much smaller recently. Twin tube fittings are usually cheaper per tube than single tube fittings. You can also get HF control gear which can be dimmed (commonly by a 1-10V DC control voltage).

    The phosphors used also have an effect. Older tubes tend to obtain white by mixing of purple with a green/yellow. This gives appaling colouring rendering. There's a measure of this quality called "Ra" which you should be able to check for different types of tubes. An Ra of 40%-50% is typical for older type tubes. Modern tubes are available which use phosphors very similar to those used in colour TV tubes. These have an Ra of about 80%. The offer higher efficiency too. Many people the better "Quality" of light they give reduces the problems they have. These modern phosphors ( often known as "Trisphosphors" ) have a slightly longer persistence - although the difference in flicker levels is small.

    You can get tubes with an Ra of almost 100% - but they are rare, expensive and innefficient.

    Colout temperature is also important. For domestic environments it is worth getting tubes with a colour temperature of 2700K which is similar to that of incandescent bulbs. This allows different types of light source to "blend" better. Offices tend to use a colour temperature of 3500K or even 4000k - which produces a very tiring "blue" light.

    If you are using HF lights then you can get tubes which offer slightly more efficiency. Such tubes must NOT be used in LF lights. If they strike at all the resulting light would be very flickery. It's usually OK to use LF tubes in HF fittings.

    When tubes get old the light output starts dropping very fast. This is the time to replace them. as the light output drops the flicker will also being increasing. Most tubes are worn out long before they fail to strike reliably. New tubes frequently swirl for the first few hours of use.

    Modern HF fluorescent lights are very much more efficient than other forms of lighting in theory. But in practice though Tungsten Halogen can rival them in many applications because because Halogen lights give a small, point source of light which is easy to control usin reflectors and lenses.

    Fluorescents - especially HF types are not a very good choice for things like hallways and stairs which only require to be lit intermittently. This is because they take several minutes to warm up. They light almost instantly - but will only deliver about 5% of their light output, gradually rising to the full level.





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