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The Truth About Flourescent Lights?
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)."
The EE is correct, the lamps go dim 120 times per second. Sine wave 0 volts, up to 150 or so, back to zero, down to -150 or so then back to zero is 1 cycle. This X60 = 120 zero's per second. If ya go somewhere that has 50hz it's a noticable difference. Buy better lights, try a Triten. (Not sure of the spelling, but much better light) Just a thought, when it's hot out, I see water on the road, but drinking it is impossible.
You get seasick because the pans are MUCH smoother than your eye normally follows such motion. Your eye does NOT smoothly follow a moving car (for example) rather it "jumps" in small increments. You get motion sick because with a smooth movie pan on an IMAX screen your eye does not have to move follow the motion yet you are still receiving the sensation of motion. This fools your brain into thinking you are moving (like if you were in the cabin of a sailboat or trying to read in a car). The reason you get sick during such motion is because such symptoms is a sign of poison in the body and it is the body's natural response to try and eject the poison. It isn't because the pans are so "jumpy" rather the EXACT opposite. StickBoy
I can't stand northern windows - the office gets too hot by late afternoon, and it's too hard to see the screen (if I crank up the brightness enough to stand out, my eyes hurt very soon).
Try 120Hz. The voltage waveform has two peaks over 1/60s, and so does power (which is unsigned).
SolaTubes are awesome! My parents added on to their house and it toatally enclosed their living room - turned it into a rather dark pit, actually. They added two SolaTubes (the room was rather large) and it made and incredable difference! Before the room had only North facing windows and you could barely read with a light - now you can easily read a newspaper in large amounts of glare-free sunlight. I highly recommend them. They are not cheep (they start around $250-$300 for the smaller ones) but if you have a dark or dim room they are worth every penny and they are a heck of a lot easier to install than a full skylight and tons more energy efficient.
Photodiodes are used on the receiving end of fiber optic cables; I've seen them happily detect gighertz range frequencies. Even if the phtodiode used above is a relative slowpoke, speedy, I just can't imagine it having any problems with piddly slow signals below a kilohertz.
I'll never forget the first time someone asked me this question. It was during a freshman physics lab (8.022), and my partner and I were 'measuring' the speed of light. The result came out to 3.00 * 10^10 cm per second -- which was really lucky considering the apparatus was basically a torisional balance, an electromagnet, an anmeter, and knowledge of how centimer-gram-erg units work. Anyway, Henry Kendall was hanging around the lab, and he quickly wiped the grin off my face when I gave him the wrong answer about the flicker rate of the lights in the room. Kendall has a Nobel prize. I trust him. If you need better convincing than that, then my hat is off to you, and let me know the results of your measurements.
Call me sick if you will, but I prefer a room brightly lit with flourescent lights, even the "cool white" variety. My eyes are quite sensitive to flicker, too. I run my monitors at the highest refresh rates they can reasonably display, I can see the flicker of a 72 Hz refresh rate if I look with the edges of my vision, and 60 Hz looks like a freakin' strobe light to me. But I've never gotten headaches from flourescent lights, and dammit-all if I don't prefer them. I guess I'm just special.
You are correct that halogen lights burn hot. They have been associated with a large number of home fires througout the U.S. I'd stick to plain old incandescent. ps-I had the headaches myself until i switched off fluorescent. Now if i could just stop the janitors from putting the bulbs back in....
I'm working my way to being an EET, so perhaps I don't know everything yet ;-), what what the hell is ABS(current)?
And how does 60 Hz become 100 Hz without some very active circuitry? Perhaps 120 Hz... But 100 Hz?
I use those bright red incandescent spot bulbs in a small lamp... deep, deep, nightvision sustaining red baby!
Comparing a flickering monitor to a flickering fluorescent light might be a case of apples and oranges. . . sort of. The rate at which one's eyes can perceive a difference in stimuli is dependent on both the rate of change of the stimuls and its intensity. Your monitor is much closer to your eyes (remember that luminous intensity decreases by the inverse of the square of the distance between the light source and the observer) and thus you are more likely to pick up on your monitor refresh.
It's much more pleasing on the eyes and creates a much "warmer" feel about the workplace, 'cuz it's kind of yellowish orange, rather than stark white.
YMMV, of course, but I dig it :-)
Just curious, because migranes atleast can be very picky about non-obviois things. "triggers" are useally everyday things that set off a migrane. Useally no one knows "why", but it could be wavelenth of the light or who knows. If its a normal headache likely its your monitor refresh rate/res/and size of monitor. Rember if it isnt 75 hz it isnt good. Also if you wear glasses or havent seen a eye doctor lately, go see get a appointment.
Wouldn't the flicker be at 100Hz since the output of the light is ABS(current) or so.
Think about it in terms of power. Power is just voltage times current. When the voltage is zero, no power goes through the light, and it turns dark. When the voltage is non-zero, current flows, and the light is bright. It doesn't matter which way the current flows; flourescent lights just care about power. In the US, electrical power is transmitted at 60Hz, which means that the voltage is zero 120 times per second. (Sketch out a sine wave...) and thus the light flickers at 120 Hertz. Or, you can also just believe me since I'm an electrical engineer. By the way, if you hold an oscilliscope probe in the air in a room with electric lights, it will pick up the electrical (60Hz) field of the light and display it on the scope.
Code by candle. I used to use two of the three wick candles and a number of large single wick candles. I had pretty good control of the quantity of light (light more candles, put some out), I could control where light was and was not, and I didn't need to turn the heat up in the winter. I've also found halogen lights to work well, probably because they bounce the light off of the walls. I like to but mine near the book case so the light bounces off the imitation natural wood grain, which gives a nice soft light.
Ahhh, another flunkie from Devry. Say no more.
You would need high-voltage DC components to do so, which are expensive. First you would need the bridge (diodes), which are common in microwaves and cost around $15, and then you would need a high voltage capacitor (otherwise you'd still get flicker!) which will be expensive as well.
Even with the bridge+capacitor there would still be some flicker; you'd need electronic regulation of some sort to get it all out, which would drive the price up further.
As some people have mentioned high frequency AC lights are in practice cheaper.
Ahh, another Linux flunkie. Never used a pipe, since you only need a keyboard.
If you means ABS as in ABSOLUTE, you would have written it |current|. But, instead, you decided to confuse the situation.
BTW: Since you are obviously the EE God, please show us the way to slow a frequency down with passive components only. No relativity crap, either! Capacitors, resistors, inductors, xformers only, please! Phase changes aren't frequency changes, and don't count... So don't bother with that (unless your magic requires them...).
Feel free to make the waveform as ugly as you like, but I see no way you can change it without a few active components. Such as transistors, fets, op amps, etc...
Btw: DeVry? What the heck you talking 'bout, smith? I thought they only said things were possible there but provided no solutions! (Ooops, sorry if that was too high a flame... Didn't mean to singe!).
I am eagerly awaiting your solution, ff to mail it to uzer@hotmail.com. I have no problem admitting my lack of knowledge here if you are successful. BTW: Please apply for a patent for your wonder device first...
Of course, no mail means no one will beleive you. Not that they should beleive me either. I don't have any proof it _can't_ be done... But then again, I'm not trying to be a scientist. Just reasoning things out by my own knowledge (however limited).
periphral (sp) vision is more sensitive to flickering. Look at a monitor with extreme corners of your eye. You will notice it flickering more. 120 Hz is still perceptible. damn my spelling suxs.
I remember seeing something in Popular Science about a 10 year old ago. A big sun tracking fresnel lens would focus light onto a collector which would pipe juicy photons to the people. Kinda a cool Idea. no wait. using the sun to heat the top of the hive is whats best for the proper gestation of young geeklings.
"is it florescent or flourescent"
neither. it's fluorescent.
We're above questions like this. Show a little resourcefulness.
Merriam-Webster's Online Dictionary: http://www.m-w.com
are fluorescent lights really linked to depression, as i've heard?
I used to have a monitor that would do interlacing at higher refresh rates (an NEC Multisync 3D if you must know). What happens is that the monitor draws every other scan line on the screen, then goes back and draws the ones it missed. It can make horizontal lines look jittery. I believe most modern OSes let you know that you are running in an interlaced mode, but I could be wrong. I would suggest making sure that you aren't.
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 it right here:
Fluorescent Lamps, etc... Faq
Lots of other interesting info there too. Like Arc Lamps, etc... );-)
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?)
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.
here 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.
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.
Erlang Developer and podcaster
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...)
Solatube 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.
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:
No, I don't work for Sylvania. :) I just wanted to share the wealth gleened from my quest for acceptable lighting.
Zeitgeist
perl -e 'print "zj5GuPW9b.sEiQQVgvL1Tr." ^ pack("H48","000f5c3312353e4a166e12311d363d3905172
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
"$30 for the One True Ring. $10 each additional ring!" -- JRR "Bob" Tolkien
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).
- AMW
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
----------------- Who is Jesus?
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.
There are better fluorescent phosphors, but most buildings and offices use cool white.
Neither, try fluorescent.
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.
... 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.
Now, my office has a window, and my offcemate and I each have new, large monitors driven at 72Hz+ refresh rates
Monty
Flourescent lights refresh at 60htz, really, really old monitors run 56 or 60.
Help us build a better map!
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.
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.
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.
.3 hertz beat frequency. That slow pulsing is real bummner.
:)
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
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?
-cf
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.
-cf
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?
-cf
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)?
-cf
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.
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 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.
This sounds like a quote right out of a guide to Feng Shui.
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?
Anonymous Coward, get it?
Not bad spelling, bad typing
...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?
Anonymous Coward, get it?
Not bad spelling, bad typing
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 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 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!
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?
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.
Bill - aka taniwha
--
Leave others their otherness. -- Aratak
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.
pithy comment
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.
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 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:
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"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
No matter what it looks like, there isn't a
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.
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?
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!
"Flame away, I wear asbestos underwear"
Real geeks code in the dark :)
-ElJefe
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.
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...