Flickering Curiosity?

N8F8 writes "Why do some people see monitor flicker more readily than others? I happen to be one of the lucky folks who can spot a 60Hz monitor from across the room. Most people seem oblivious to this flicker. Other people can only see it in their peripheral vision. I tried researching an answer and I stumbled on plenty of information about something called 'Critical Fusion Frequency'. There even appears to be quite a bit of research into this phenomena but I couldn't find much information on why flicker perception varies so greatly. Can anyone shed some (flicker-free) light on this?"

Comments

I see Flicker at other refresh rates....

[haplo21112]

...it seems to depend on the day and the lighting, my level of awakeness...and seemingly even mood...

Often if I change from using my laptop on LCD, or Projector back to monitor, I will be bothered by flicker no matter what refresh I set for a while.

flicker sucks.

[grub]

I can walk into an office at work and spot a 60Hz monitor flickering instantly. Usually I'll ask if the person's eyes get tired, etc. and fix it for them. More often than not they report the eye irritations are reduced.

Re:flicker sucks.

[SilverspurG]

Usually I'll ask if the person's eyes get tired, etc. and fix it for them.

Wrong spin. The person's eyes have adjusted to by in sync with the 60 Hz refresh and they are not bothered by it. Your eyes, for some reason, never figured out how to sync.

My eyes sync at whatever refresh is available.

Re:flicker sucks.

[Anonymous Coward]

Nah, some people will complain that their eyes are tired after hours on a computer. A refresh fix eliminates that in many cases.

flicker..

[jotux]

Thank you! People always think I'm strange because I don't like crt monitors. I always see flickering, especially when I move my eyes from one position on the screen to another. Flickering is one reason I love my laptop, and rarely go around desktops anymore(excepting desktops with lcds).

also

[same_old_story]

distance plays a big role on this. from a distance (6 feet +) you can usually spot flickering monitors very easily.

Re:also

[museumpeace]

SPATIAL DOMAIN:
Yes. Distance is critical. Because of interleaving, you have neighboring rasters 180 out of phase...and that is intended to reduce percieved flicker. If you happen to view a monitor from such a distance that the space between even numbered [or harmonics ] rasters approximately projects to the retina at the spacing be individual receptors [rods? cones? idunno] you might undo some of the interleaving effect. This won't be a strong phenomenon because receptor cells are not layed out in a grid.Less than 6 feet and imaged raster separation may exceed receptor spacing, [you begin to be able to actually pick out rasters on a low quality screen but you don't see flicker], greater than [what would it be ? 10, 12, 20] feet projected raster spacing is well less than recpetor spacing so each receptor is summing [ie averaging out] interleaved raster pairs and you can't see flicker.

TIME DOMAIN:
ever noticed flicker [ in periperal vision in my case] if you are looking off to one side of a monitor across the lab WHILE SOMETHING BUMPS YOUR HEAD? I had to stop the experiments I was doing to get to the bottom of this phenomenon before anyone caught me just standing there looking into space and banging my head with my hand. [sometimes life is just strange but would it add or subtract from your comment to have it modded "Strange"?]

Re:also

[Mr. Slippery]

ever noticed flicker [ in periperal vision in my case] if you are looking off to one side of a monitor across the lab WHILE SOMETHING BUMPS YOUR HEAD?

No need to smack yourself in the head - put the end of a plastic fork between your teeth and pluck it. Vibration goes into your skull, and you can see all kinds of cool flicker on a CRT.

Not just 60 Hz

[Alternate Interior]

There are a number of refresh rates that I notice.

• 60 Hz is painful
• 72 and 75 are usable, but I notice
• 85 looks natural
• 90 is similar to 75
• 100 and 120 looks similar to 85

It doesn't make sense that 90 is worse than anything else at 85+, so perhaps it's just the particular monitor. And I won't claim I can identify everything. I can't differentiate 85/100/120, or 72/75/90. But amongst the three groups of refresh rates, I can identify the group.

Re:Not just 60 Hz

[Zoyd]

I have no problems with 60hz on my 20"... though on everything else I can simulate an LSD flashback just by crunching an ice cube.

Ice cubes should not be chewed. The coldness cracks tooth enamel.

Annoyed by flickr

[geoffspear]

God, please make the endless stream of bad cameraphone pictures go away!

Wait, what's this about refresh rates?

Fluorescent Lighting?

[Sparr0]

Sometimes I can see it when it coincides with the frequency of the lighting in the room, or is off by some small amount.

Re:Fluorescent Lighting?

[AndroidCat]

Sometimes I can really see it when I've been out the night before and it coincides with the frequency of the throbbing of my head.

Everybody's different

[jgardn]

I'd like to think that I have the same ability because I have spent so much time in front of monitors. But I know a lot of people who have spent many many more years and who still can't see it.

I've marked this one up long ago to one of those weird attributes we're born with or we learn or that is a combination of both. I know that a lot of people thank me for raising their refresh rate, but there are some who can only work at about 60-65Hz and can't stand 75Hz or 80Hz, which is where I am comfortable.

I've also fallen in love with LCD screens. I can finally work without getting tired! Now if only my mind could keep up with my eyes.

I still use a CRT at work and that's led to the pile of notes and graphs and charts I've draqwn up and strewn about my office. I have to take a break from time to time or I can't look at the screen.

Re:Everybody's different

[Anonymous Coward]

I'm with you 110%. As a long-time tech, I've seen the same things for ages. I have to bump up the refresh to gain comfort for myself; I even have had to wear glasses (tinted, polarized, no correction) when I work long hours in front of a CRT. Not so with a LCD, however. And, as you've stated, it varies with other folks, some at higher freqs and others at lower freqs.

Now, for something new (and related). I also tend to see the flicker in the florecent lights. To make matters worse, the two (lights and CRT) are never in sinc with eachother, greatly increasing the effect. This makes headaches more common. Some people are sensitive to the lights, but not the CRTs (if they've been adjust out of the 60hz range here in the US). For clients who are sensitive, I usually end up replacing the lights and the CRTs to get rid of their issues completely.

And, on a slightly different angle, I can also tell you when your flyback transformer is going bad in your TV because.... You guessed it, I can hear the dang things! This leads to the obvious question: are the two sensitivities related? Again, I know people who can hear the buzz of a TV and others who think we're all nuts (I am, but that's unrelated). It isn't just the transformer going bad that is noticeable, but the screen itself to those of us who are very sensitive.

Now, to tie it all together, I have circamstantial evidence that all of this runs in families. My family has it up through my mother's line. Most of my friends not only do not have it, but it doesn't show in any of the family members that I've asked about this (that's most of them, I'm also an Anthropologist). I have found a couple other families where there is a line of parentage with this 'ability'. Not all offspring will inherit it, but, it seems that most do (dominant trait, possibly).

Anybody have anything on all of this?

Ummm People are different

[yasth]

You will tend to notice it more out of the corner of your eye then head on. (Go ahead try it now), that is because the rods are more sensetive to motion.

Also some people don't notice it because it is all they have ever really used. A lot of people just assume their monitor sucks. They notice it but have no idea what causes it.

Lucky?

[Tom7]

Why do you consider that lucky?
I'm often annoyed by effects that other people don't perceive, and I personally find it, well, annoying.

Re:Lucky?

[Neil Blender]

I think he means it in the way that someone might say, "I'm one of those lucky people who have explosive bouts of diarrhea eight times a day."

I didn't read TFA, but...

[xami]

..Toshiba, I think, made some tests in cinemas with 30fps and 70fps movies to see howmany people could distinguish between single frames.
Surprisingly, a lot of them couldn't even notice the difference but there was a significant number (15% afaik) who could even notice single frames in 70fps

Audio corollary

[MrScience]

I can pick of the horizontal frequency of almost any television from more than 10 feet away. I can tell when the TV is on before I even enter the room... but everyone else in my family doesn't seem to pick up that frequency (15750hz?).

Re:Audio corollary

[cniebla]

I can pick that noise too, but with an interesting twist: I actually can use it like some kind of sonar, really. Sometimes I'm on my laptop, giving my back to the door in the room, and to avoid a "comming-from-the-back-making-no-noise" joke, I just turn on the TV, with the sound mutted. It can give to me the actual position / movement from even a cat coming by, so no more jokes ;). By the way, where you found that freq.? (15750hz)

Re:Audio corollary

[Flying Purple Wombat]

You mean that most other people can't hear that noise? I thought that most everyone could, and I was the only one who was really annoyed by it.

Most people can't hear it. It used to drive me crazy, I could hear CRTs, ultrasonic motion detectors, and other things that most people can't. As with many things, this is an individual variation. My son inherited this ability, but my daughter did not.

Now that I'm 0x29 years old, I can't hear a CRT unless my left ear is within 6 inches of it (my right ear can't hear it at all). High frequency hearing loss is common as age increases. In my case, loud music and pyrotechnics accelerated the process.

Re:Audio corollary

[narcc]

This link will explain it all

Re:Audio corollary

[cavemanf16]

I get so annoyed with my wife for always forgetting to turn the TV off after turning off the stereo and other A/V equipment because I can hear it, even from a couple of rooms away. I also notice the 60Hz flicker in computer CRT screens, but 75Hz+ is fine. My eyes actually get really tired when trying to use a 60Hz monitor.

I actually think this phenomenon has to do with brain power and raw brain ability for intelligence. I remember my wife mentioning that she read somewhere that if a cat is prone to watching TV, it's slightly retarded because to a normal cat the frequency of images appearing on the TV is too slow - hence it usually ignores it as "motion" since to the cat it's just a picture hanging on the wall that changes too slowly to be considered interesting I guess. Interestingly, we have two cats in our house. I've caught the dumber one looking at the TV every once in a while. I measure dumbness in our cats based on how well they respond when their name is called, whether they are capable of informing me when they need food, how "sneaky" they are when trying to jump on the counter, etc. One of them is good at all of that, the other is definitely NOT. The stupid one just lets our dog pester her to death and starts crying when he's getting too rambunctious, the smart one knows where to "escape to."

I'll have to try that whole "mute the TV" to act as sonar thing sometime though and see if it works for me.

the sound is unbearable

[St. Arbirix]

Who else can hear the sound a television or monitor makes? I can tell from another room when a TV has been turned off because the high-pitched squeal goes away. Those electronic mosquito repellers are equally annoying.

I've read in various places that women can hear higher pitches than men but I've yet to meet anybody male or female who could hear some of the crap I put up with. Walking into a computer lab is the same to my ears as diving to the bottom of a pool.

Re:the sound is unbearable

[bill_mcgonigle]

Some department stores have security systems that cause the same effect. For me, anyway, the sound of a blank TV sounds different than a typical high-pitched sound. Does it for you?

One source of very-high-pitched sound perception (~26-28KHz) is sympathetic vibrations of the ear bones. Normally the sound waves vibrate the tympanic membrane and the ear bones pick it up and transmit it to the cochlea which fires the nerve. But sometimes the bones can be vibrated directly which results in the perception of a high-pitched sound, higher than the tympanic membrane can respond to. This is one of the chief complaints of the 44.1KHz limit on CD's - they can't represent frequencies over 22050Hz, and people can perceive higher pitches even if they can't 'hear' them with the eardrum.

Perhaps that's somehow involved here. Just a guess.

Re:the sound is unbearable

[vidnet]

A TV/CRT has no moving parts. The movement of the beam is controlled by magnetic fields.

Re:the sound is unbearable

[dpbsmith]

Hee, hee... when I was a kid I could hear the 17,750-cycle horizontal scanning frequency (as it was then... it became 17,734 at about the same time it became "Hz") clearly. I'd ask adults about it. And none of them knew what I was talking about. When I was about ten I finally insisted that someone turn a TV off and on, with the volume all the way down, in an adjacent room, so that I could _prove_ that I could tell whether the TV was on or off and wasn't just imagining things.

When I was in my twenties, I went to a dentist who used an "ultrasonic" cleaning device that was audible--and painfully loud--to me. I complained. They insisted that I couldn't possibly be hearing it because it was "ultrasonic." I said, "Oh? How do kids react to it?" They said, "Oh, we don't use it on kids, they jump out of the chair when we do." But they still didn't believe that it was because I, and the kids, heard it.

Also in my twenties, I visited the mineral and gem room of the American Museum of Natural History, which I had visited many times with pleasure, and this time I confronted with the loudest "ultrasonic" sound I've ever heard the displeasure of hearing. I'm pretty sure it was higher than 15,750 Hz. Heaven only knows how many DB it was. It didn't even sound like a high-pitched done; it sounded like someone was clamping my head in a vise. It gave me a splitting headache within about five minutes. There was obviously some kind of standing-wave effect because if I moved my head or walked around it would fluctuate; I probably could have determined the wavelength if I'd thought about it, but I didn't.

It got louder whenever I got near some little boxes mounted on the wall about ten feet. They were inconspicuous and painted black but in plain sight.

I went to the guard, and said that it was daytime and he was on duty, would he mind turning off the ultrasonic burglar alarm because it was giving me a headache. He sort of freaked out. He said that they didn't have any ultrasonic burglar alarm and what was I talking about? I said I was talking about the extremely high-pitched, extremely loud sound that was coming from those boxes on the wall, and pointed to them. He insisted that they were not part of a burglar alarm system and were not making any noise.

I don't know if he a) thought I was delusional, or b) was upset because the system was supposed to be top-secret, or whether c) I _was_ delusional... you figure it out.

Well time took its toll on the old hair cells, and I got the twentieth-anniversary special CD of Sergeant Pepper's Lonely Hearts Club Band in 2000 and listened to the band that supposedly has an ultrasonic tone at the end of it... on my headphones... with the volume turned pretty high... and you know what? I couldn't hear a thing.

Maybe I can visit the American Museum's gem room in comfort now.

Re:the sound is unbearable

[ballpoint]

Typical TV sets whine at 15kHz. That's not a very high frequency; most of us _should_ be able to hear that. CRT monitors are a different beast; the >60kHz line refresh should be unhearable, were it not for subharmonics. Try filling your screen with 5 lines of white alternated with 5 lines of black. Chances are you'll hear something. (for the clueless: don't bother to try that on your LCD).

Some other loosely related stuff:

- More than twenty years ago remote controls used ultrasound. I could hear them from across the room, even though they were 40kHz or so. Subharmonics at play again ?

- I used to be bothered by an irritating feeling while studying in the evening in late spring (in addition to have to study during spring evenings). I quickly found out that the cause were bats. My desk was facing a window, which was opened 45 degrees to the inside. The pings from the bats reflected on the glass pane, right into my ear.

- As to flicker: anything less than 100Hz bothers me. I find (compact) fluorescents with a non-electronic ballast intolerable. Things may be better in the US (120Hz instead of 100Hz here).

Re:the sound is unbearable

[mc6809e]

Doubt the fluorescents would be better here... AC is 60 Hz, 120 Volts here, not the other way around.

Ah, but the light flashes at 120hz. When the current is near 0 A, the light goes out, and that happens twice for every cycle.

Re:the sound is unbearable

[St. Arbirix]

Well time took its toll on the old hair cells, and I got the twentieth-anniversary special CD of Sergeant Pepper's Lonely Hearts Club Band in 2000 and listened to the band that supposedly has an ultrasonic tone at the end of it... on my headphones... with the volume turned pretty high... and you know what? I couldn't hear a thing.

CDs, with a 44kHz sample-rate, can only play sounds up to 22kHz. I'd bet anything that the ultrasonic tones can be heard on the LP version of that album. I'd also bet that that section of the album would be perfect for figuring out if you need to replace the needle on the record player or if the album has become too worn.

Re:the sound is unbearable

[rco3]

Your post is curious.

Parent poster is referring to the whine that a TV makes, caused by mechanical vibrations in the windings of the flyback transformer. The whine is at the line retrace frequency, or about 15 kHz. A similar noise can be found in a computer monitor if it's a CRT type, but not in an LCD or plasma.

You mentioned Johnson-Nyquist noise. Johnson noise is broadband 'white' noise, caused by random thermal motion of charges in a resistance. It can be amplified in an audio system and be reproduced by the speakers, expecially if the gainstaging is incorrect ("the TV volume is on full blast but the reciever volume is low"), but if people around you say they can't hear it - dude, they're fucking with you. White noise has the same power at all frequencies, and the only way to not hear it is to be stone deaf. They may have gotten used to it and be willing to ignore it, but that's not the same as being unable to hear a 15 kHz tone.

Now, if you hear white noise in "everything", you may in fact be nuts, or have some serious hearing issues that need to be checked out. A computer monitor with no speaker, e.g., should emit essentially ZERO amplified Johnson noise. Interestingly, a case fan or CPU fan should emit fairly 'white' noise with some relatively constant tones mixed in.

In any case, parent poster is NOT referring to Johnson noise, he is referring to flyback whine.

Oh, and you misspelled 'reciever'.

Re:the sound is unbearable

[gid]

To test yourself / your computer's sound system, try in_tone.dll for winamp. Just drop it in your plugins directory, and copy the below to a .m3u file. I can hear 20k, but just barely. Hard to say if it's the actual tone or some weird subharmonics thing going on.

--- begin tones.m3u ---
tone://20,10
tone://25,10
tone://30,10
ton e://35,10
tone://40,10
tone://42,10
tone://45,1 0
tone://50,10
tone://55,10
tone://60,10
tone: //80,10
tone://77,10
tone://110,10
tone://120,1 0
tone://156,10
tone://220,10
tone://311,10
to ne://440,10
tone://622,10
tone://880,10
tone:// 1200,10
tone://1800,10
tone://2600,10
tone://35 00,10
tone://5000,10
tone://7000,10
tone://1000 0,10
tone://11000,10
tone://12000,10
tone://130 00,10
tone://14000,30
tone://15000,30
tone://16 000,30
tone://17000,30
tone://18000,30
tone://1 9000,30
tone://20000,30

Here's something...

[Otter]

I don't have time to research this thoroughly but figured I owed you something in return for your informing me of the existence of Google Scholar...

From Shane Sidebottom's Masters thesis:

One factor that is not often examined in the flicker research conducted in psychophysics is individual variability. Some people are more sensitive to flicker than others (Rogowitz 1986). To develop an accurate flicker standard for the general population, the nature of the distribution of flicker sensitivity in the population must be considered. Individual differences may be attributable to many factors, such as gender, age, or personality. Young people are more sensitive to flicker than older people (Kim and Mayer, 1994). Women are more sensitive to flicker than men are (Maxwell, 1992). Personality has been cited by psychologists as affecting flicker perception (Amir and Ali, 1989). The factors that lead to individual variation in flicker sensitivity may be of little real use to those designing displays for the average user; however, knowledge of the extent of individual variability is useful.

There's more (plus a graph!), and the references should keep you occupied for a while. As to *why* -- well, *why* is a question that can keep researchers busy for quite a while.

Monitor Whisperer

[Neck_of_the_Woods]

I can tell you anything you need to know about your monitor. They speak to me, in a very high pitched form of basic.

Let me hold your monitor cord, press my forhead to your screen, or if possible....mount your monitor. I will gleem everything I need to fr..errr everything you need to know from your montior.

I am not a frequency biggot, I like'm fast, slow, flickering, fleckering, high pitched, low pitch...I don't give a damn...just let me have go.

Big shocker!

[Cuthalion]

Surprise! It's a natural phenomenon that fits a normal distribution!

Re:Big shocker!

[Inthewire]

What are the odds of that happening?

New LED tail lights...

[Drunken_Jackass]

are annoying to me. I can see them flicker in my peripheral vision and it's damned annoying. I figured that they musts oscillate around 60Hz or so, but does anyone have any more information about them?

Re:New LED tail lights...

[Flying Purple Wombat]

The brightness in some LED assemblies is controlled by pulsing the current at a varying rates. Changing the ratio of on/off time changes the percieved brightness. They really do flicker on the dim settings.

Re:New LED tail lights...

[norkakn]

the dc system in a lot of cars is just a really simple rectification of an ac signal, so there would be a flicker (even with a LPF, if it were going 12v-15v at 60hz, some people might be able to see it)

variable refresh rate

[Froze]

Others have mentioned that they only get bothered when switching from one display to another. I think this is because your brain (optic whatever) can vary the uptake rate of information from your eye.

Test it out, try laying on the floor beneath a ceiling fan on low or medium. If you watch fan long enough you can stabilize the apparent interference rotation rate of the blades.

When you can vary the rotation rate at will, you have less chance of being annoyed by flicker since you adjust rapidly. If you can't see the rate change then your eyes can't compensate for the flicker. Hence they get tired more easily.

A simple answer..

[stefanlasiewski]

Can anyone shed some (flicker-free) light on this?"

Simple-- YOU are a robot, THEY are not.

Nerves and the brain...

[tRenn]

Ok, I'd like to know if there's a fundamental frequency that the average human's optic nerve/brain refreshes that make us comfortable with viewing CRTs at various refresh rates?

Re:Nerves and the brain...

[snooo53]

There isn't really a fixed frequency at which nerve cells operate/communicate at. The first thing to understand is that the rate at which nerves fire generally varies according to the intensity of the stimulus.

Furthermore, there are many different types of nerve cells and receptors in your eyes. Some only respond to certain features based on the shape of the cell. Some only are activated with a certain intensity of stimulus. Some are only activated when a stimulus changes. Some are only activated when certain combinations of neighboring cells are stimulated.

So the short answer is there is no fixed "refresh rate" of the brain. There is so much we don't know about the nervous system it is amazing. Over 50 neurotrasmitter substances have been identified, and there are more out there! We dont know exactly what half of them even do. Research into these types of questions is really on the cutting edge of science so there are a lot of unanswered questions out there...

Human Perception

[Anna Merikin]

Human perception varies widely. In the season he hit .406, Ted Williams, in answer to the question, "How do you hit so well?" replied, "I wait till the ball is as big as a watermelon and I can see the stitches and the printing on the hide and then I smack it."

To explain how he alone avoided a terrible accident around a blind curve during a Grand Prix roadrace, Juan Manuel Fangio explained that as he drifted around the turn at about 120 mph, he became aware that the crowd along the side of the track was not watching him, but had turned their faces ahead and that gave him the clue to slow down as there must have been big trouble in the curve.

Human perception varies greatly, or did I already say that?

I do not usually see flicker, but some CRTs are better or worse than others. I cannot tell the difference between smoothed fonts and others. But I can sure hear a tiny bit of distortion above 10kHz! Even so small an amount that others cannot detect it drives me into the pain zone, so I have to choose my audio components very carefully.

Human perception varies greatly.

My 2 cents...

[MrIcee]

While I am not a vision researcher I have spent countless years in digital imaging and understand some of the basics of what is going on.

The 60 hz frame rate (or actually, 2 fields at 30 hz) and the vertical retrace period can be viewed by just about any person - regardless of gifts....

Think you know someone who can't see the flicker? Have them stand about 15 feet away from a monitor and chew a stick of gum - they will be amazed to see the jitter (or just pretend to chew a stick of gum or bob or weave VERY slightly on your toes).

Not everyone is wired exactly the same and some of us have eye sensitivity - what we can actually consider a 'sample rate' that is higher, or lower, than the norm. In effect, what you are seeing when you see the jitter can be likened to aliasing effects - every now and then your sample rate syncs up (or desyncs slightly) and you catch the vertical blanking interval and/or scan itself.

It is well known that dogs and cats in general don't see TV like we do - because their vision system is at a faster rate than ours - to them the screen looks like a lot of weird angled lines. However, everyone knows about that ONE cat or ONE dog that DOES watch TV - most people think they are gifted but instead, they are 'slower' in their vision system.

Consider as well, car tires. As you go down the road they spin but you are very familiar with the effect of them 'apparently' spinning backwards - again, the sample rate of your eyes is just slightly out of sync with the rotation speed (or harmonic of) causing the hubcap to appear to turn backwords. And if your right in sync with the speed (or harmonic of) then the hubcap appears to be standing still (e.g., in it's rotational axis).

If you were to consider two people, looking at the same tire rotation, they would undoubtedly report slight differences in what they see. The same effect is happening on the screen - the refresh rate is similar to the rotating hubcap and you are just slightly faster or slower than it is.

(btw, yes, I've been able to see it for years and years and year)

Re:My 2 cents...

[NereusRen]

"As you go down the road they spin but you are very familiar with the effect of them 'apparently' spinning backwards - again, the sample rate of your eyes is just slightly out of sync with the rotation speed (or harmonic of) causing the hubcap to appear to turn backwords."

The optical illusion of rapidly spinning objects "freezing" or starting to spin backwards when they hit a precise speed has nothing to do with the "sampling rate of your eyes," since there is no such thing.

Rather, it depends on the object being lit by a flickering source (roadside lights at night), or recorded on a flickering medium (movies with a certain number of frames per second). You will NOT be able to see the effect in-person under bright sunlight.

Also, people won't report differences in the effect, since it doesn't depend on their eyes. Anyone can see it, "gifted" or no. It is quite different from monitor flicker in that respect.

obviously

[jago25_98]

Seeing as I can detect 60hz easily it must clearly be a sign of superior intellect

come on, you thought it

Re:Shouldn't it be?

[Nynaeve]

What's the refresh rate on life?
5.391 × 10^44 Hz

Re:LCD Response?

[PornMaster]

LCD pixels don't go dark between refreshes of what's on the screen. CRTs only light up a pixel when the electrons hit the phosphor, then dim until hit again. The LCD pixel stays lit between changes.

Beats

[Anonymous Coward]

The issue at hand is constructive interference.

90 Hz will interact very strongly with all the things around you that do pulse at 60 Hz. Fluorescent lights are the main culprit here, but almost anything may, since the A/C is being provided at 60 Hz.

Two out of every three refreshes on the 90 Hz monitor will not coincide with the lighting flickering, but one will. That results in a weaker 30 Hz flicker on top of the 90 Hz.

Re:Beats

[Fascist]

A/C is being provided at 60 Hz.

Most countries privide AC at 50Hz. Only a handful of countries use 60Hz, even though it is the most effective for delivery of AC over long distances. Nikola Tesla recommended 240V at 60Hz after experiments with AC.

Re:Beats

[FrankSchwab]

Actually, neither of the parents points are particularly true. http://forums.anandtech.com/messageview.aspx?catid =50&threadid=1531887&enterthread=y is a discussion on another board with some good info from PowerEngineer.

Broaden you scope, Idealist

[Linux_Bastard]

In CRT based TV's the high voltage power supply vibrates.

Not to mention the macro item such as the speaker cone, buttons and knobs.

At the micro level you have lots and lots of e- and plain old heat.

Quick quiz,
How many moving parts in a solid state piezo tweeter?

The moment on the CRT's flyback is more than in that piezo tweeter.

Critical Flicker Frequency

[Telvin_3d]

You might also want to look up "Critical Flicker Frequency" I am fairly sure this is either the same thing or a related thing. It describes the effect that allows for movies and other moving images based on rapidly shifting images.

Re:Thats just how the human body works.

[BeaverCleaver]

Simple. Hershey tastes like vomit.

Re:Thats just how the human body works.

[cloak42]

Wait, everybody can't hear that high-pitched hum that TVs and monitors make? Jeez, I always wondered why I was the only person I knew who was really annoyed by it.

Monitor flicker is one of the biggest annoyances to me... I can spot a 60Hz without any difficulty whatsoever, and I can see a 72Hz or 75Hz refresh rate out of the periphery. I personally can't deal with anything less than 85Hz unless I absolutely have to. It's one of the reasons that I often have my monitor's resolution lower than I'd like. For example, my second monitor at work (I use a laptop with its screen as the primary monitor), an NEC 19", would happily run at 1600x1200, but only at 60Hz. I wouldn't wish that on my worst enemy, so instead I run it at 1280x1024@60Hz. It's just better that way.

Toothbrushes Also Work

[wintermute1974]

If you really want to experience something amusing, bush your teeth with one of those powerful, pulsating electric toothbrushes while trying to read a CRT monitor.

Watch as the illusion of reality that your brain creates for you breaks down as it hits an edge-case of monitor refresh + head vibration that a few hundred thousand years of hunter-gathering never equipped you for.

Of course, once you start here, you might want to explore other mind hacks that are also available to you.

Car wheels don't do it

[gr8_phk]

Vehicle wheels only appear to be going backwards in 2 cases: 1) they're on film/tv where aliasing happens due to the "sampling" with each frame. 2) for it to happen live you need a strobe light - i.e. driving at night under bright non-incandecent lights (quite common). There is no "frame rate" for the eye, so this normally doesn't happen with real observed objects. You may also notice some intereting things when parts of the wheel shadow other parts - the large lugnuts on big trucks sometimes do this in the right light.