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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?"
...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.
Power Corrupts,Absolute Power Corrupts Absolutely, leaving one person(group)in charge is absolutely corrupt.
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.
Trolling is a art,
I bet this is also related to the differing perceptions of LCD response times?
I happily play FPS games on my LCD, without any noticeable blurring, but I know many people still view it as a problem on LCD's.
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).
distance plays a big role on this. from a distance (6 feet +) you can usually spot flickering monitors very easily.
BTW, _which_ article should we read?
Slashdot: Failed Car Analogies. Amateur Lawyering. Anecdote Battles.
- 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.Implicit Evaluation with PHP
Wait, what's this about refresh rates?
Don't blame me; I'm never given mod points.
Sometimes I can see it when it coincides with the frequency of the lighting in the room, or is off by some small amount.
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.
The radical sect of Islam would either see you dead or "reverted" to Islam.
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.
I'd do something interesting, but my server can't handle a slashdotting.
Different people can percieve different things. Some people have an extra type of receptor in their eyes. Some people can hear the high pitched noise that various components in an average CRT make when they are poorly tuned. Some people cant tell the difference in Hershey and Milka :)
I've always had excellent peripheral vision, which is a blessing and a curse. It seems to me the flickering is worse when viewed peripherally. I had a co-worker when I was in a 'bull pen' (no cubes, just rows of 'puters) and the flicker on his monitor drove me nuts. My flicker didn't bother me as much, but it was short-lived as I got brave and set mine higher on my own (we where contractors at the time.)
"Well..here I am..." - Jubal Early
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.
What does that mean if every monitor I look at has a perfect picture but sometimes it's the rest of the world which seems to be flickering?
What's the refresh rate on life?
fast as fast can be. you'll never catch me.
..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
I don't see the monitor flicks or what but I can hear whether monitor is switched on or not (and the same applies to tv). The annoys me most when I start to use ADSL (few years back) and chatting on the same line through the phone since the filter doesn't take out the whole spectrum of mine. My flatmates doesn't have any problem with it though so i think it is just me.
Essentially I think noticing the monitor flickers and hearing the noise from tv is more or less from the same reason, human are different from each other. I would guess this is something born to be but not too sure if it is trainable. I think you just happen to take light at some specific frequencies which makes you able to notice the flicks.
I am harvesting funny/good quotes. Please help by putting them in your sigs
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?).
You quitting proves that the karma kap worked. The most annoying of the whores shut up. --CmdrTaco
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.
Direct away from face when opening.
I've flat out refuse to use one brand of monitor we have at work, even at 85Hz they give me a headache after about 10-15min.
:/
The LCD's at work ain't much better as there cheap things, so basically I'm limited in what PC's I can use at work...which is good and bad
Anything at 60Hz is just plain crazy in fairness!
"WebTV: bringing the Internet into the shallow end of the gene pool since 1995" - Martin Bishop
From Shane Sidebottom's Masters thesis:
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.
What I'm listening to now on Pandora...
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.
Neck_of_the_Woods
#/usr/local/surf/glassy/overhead
Surprise! It's a natural phenomenon that fits a normal distribution!
Trees can't go dancing
So do them a big favor
Pretend dancing stinks!
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?
There are 01 types of people in this world. Those that understand binary, and me.
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.
-- The morphemes of your disquisition are ascertainable, but they have eschewed an ambit of transpicuous exposition.
You see more flicker than other people ... yet you think that you're LUCKY?
I don't know much about the research, but my own experience is that I'm very bothered by low refresh rates. Looking at a 60Hz screen gives me a headache in less than 60 seconds. 75Hz is unpleasant after a few minutes. I can work at 85Hz, but I can tell the difference between 85 and 100Hz. I can't tell the difference between any frequencies over 100Hz. I've worked with people who literally can't tell. I'd switch back and forth between 60Hz and 100Hz, asking them to evaluate each, and they could see no difference.
This isn't as much "normalization" as it is "don't take so many drugs when you're designing tables."
Television in Europe is awful for me. PAL has a different refresh than NTSC and whether it's higher or lower, it gives me a nasty headache after a while.
Can anyone shed some (flicker-free) light on this?"
Simple-- YOU are a robot, THEY are not.
"Can of worms? The can is open... the worms are everywhere."
The DLP rainbow effect is something else many people don't notice, but it really bothers me for the first 15 minutes when watching something on a DLP projector. Even after that, I see it from time to time when my eyes move quickly.
Most of this is from Wikipeida: The normal human "Critical Fusion Frequency" is around 16 Hertz. This could explain why monitors acting at specific frequencys (multiples of 16hertz?) bother people more. (if 85hz bothers someone then 101 may bother them as well)
I would assume this is simmilar to how a helicopters blades will appear to spin backwards when they are starting. Your eyes 'take a picture' each time the blades have almost made a full rotation. So all you see is that the blades have moved back just a little when really they have gone all the way around.
If Your eyes 'take a picutre' when the monitor has refreshed exactly 4 times (for a 60 hertz monitor) then you may see a solid image, however if you're eyes are little slower for faster then the image will begin to flicker in the same way that the blades of the helicopter spin backwards.
One of the reasons that lcd monitors don't do this as much is because they dont actually 'refresh' the same way as CRT's, only the parts of the image that have changed are physically changed on the screen. In contrast a CRT monitor constantly has a beam of electrons that is scanning across the screen at whatever the refresh rate is.
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?
I'm wondering if there is any correlation between the people who notice 60Hz flicker and the 'lucky' 5% who are disturbed by the 'rainbow effect' caused by single-chip DLP systems (and slow and/or 3-4 segment color wheels).
Anecdotally, I am afflitced with the ability to see both.
-Turkey
Most of the time, I don't notice my monitor flickering. However, if I have sinus pressure (cold, allergy, whatever), it drives me nuts even at 75 Hz, and even fluorescent lights have a noticable flicker.
If God had meant for man to see the sunrise, He would have scheduled it later in the day.
I happen to be one of the lucky folks who can spot a 60Hz monitor from across the room.
Don't you perhaps mean unlucky? Most public terminals (Win) are set at the lowest rate of 60 Hz, regardless of the capability of the monitor. Makes it hard to concentrate at the library, etc., with crazy flicker in your peripheral vision.
Is the low refresh of some LEDs visible to many people as well (leading to flashing in the peripheral vision)?
I have noticed that after being outside on a bright sunny day my 75Hz refresh can be noticably flickering when previously it had been fine. Or maybe after more than the usual amount of coffee. So the effect can not only vary from person to person, but also within one person's experience depending on the amount of light stimuli previously presented . I wouldn't know the actual reason for this and any theories I might have would probably be wildly off base. But based on htat observation I would think maybe a polarizing filter put in front of the screen would noticeably reduce the effect of flickering at any given refresh rate. I am going to try that with my sister's polarized sunglasses here in a minute.
>>>>>> Chewie, take the professor in the back and plug him into the hyperdrive.
The NERD!
Able to spot a monitor flicker in the blink oif an eye!
Heres how!
Need electric tooth brush, monitor, one mouth.
1)Turn it on tooth brush put in mouth and bite down on it.
2)Look at monitor.
3)um... Profit!?!?!?
I can see Flicker. It's the reason why I've cycled through four different monitors in the last year, before finally settling down on a Sony SDM-HS94P (flatscreen). Any refresh rate less than 72 is intolerable for me, and even faster refresh rates are noticeable when I move my eyes or look at it in my perhipheral vision.
What's worst is eating crunchy food. The jarring motion of biting down on someting crunchy apparently jolts my head at the same speed the screen is refreshing, so the image breaks up for a second. If I'm eating a lot of crunchy things, it makes a CRT unusable.
The oddest part is I can see "Flicker" on LCD screens. It's not flicker like on a CRT (you know, from seeing the refresh line move across the screen from top to bottom), it's seeing the individual pixels refresh at a 60Hz rate. So the problem is, on a lot of LCDs, when I run my eyes from the left to the right, my eyes will track at exactly the refresh rate of the screen, and the pixels break up and swim.
I don't know if that makes sense, lemme see if there's a better way of explaining it. Ever see those flashing lights they like to use in Vegas, or at carnivals, where every other light alternates blinking on and off? If you just stare at one, you just see a light turning on and off, with the neighbors alternating. But if you look at it from a distance, it creates the illusion of motion. If you run your eyes from left to right across it at exactly double the "speed" of the lights, your eyes will hit the next natural frequency and the lights will be appearing to move twice as fast. That's what's happening with the LCD screen. The pixels swim when my eyes move at the refresh rate, and the image breaks up. My eye also throws an event (so to speak) that it's seen motion on the screen, so when I'm doing something, like, say, writing a paper, and move my eye to the top left part of the screen, the screen swims, and it breaks my concentration. I tried getting used to it, but it eventually got so frustrating to me that I had to return it.
And apparently I'm the only one who can see it. I returned that LCD to Fry's and they just looked at me like I was crazy. "Don't you see it??" Fortunately, it also had developed two stuck pixels in a week since I bought it (and it was still under warranty, natch) so they didn't think I was too odd, but I did notice when I was starting at the rack of LCD monitors they have for display, I was the only person who could see the refresh problem on the monitors. I can see it on about half of them. And it's not even per model. I've looked at three Sony HS94Ps now, and I bought the only one that didn't have the problem. My current one, if I try really hard (defocusing my eyes and running it from left to right at fast speed) I can get the pixels to swim, but it doesn't happen at all during normal use, and that's good enough for me.
Getting out of CRT flicker hell has made my life much more enjoyable.
-Bill
It might have something to do with interference of the monitor with the light coming from TL-tubes. Then again, I get raving mad from a monitor flickering at 60Hz in a room that is lit by sunlight.
-- Cheers!
...as you can see here.
The biology behind it also explains why birds and bees can fly at ludicrous speeds through tree branches without hitting a thing, but we can barely navigate the mall.
There also seem to be some people who can hear frequencies way way beyond what they are supposed to and can hear the high pitched whine of the CRT's flyback transformer also (or are they hearing a sub-harmonic?)
Anyone here can do that?
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.
i will say i use 1024x768@70 on my (low end) monitor instead of 1280x1024@60 because the latter is annoying.
When I was a kid (and still nowadays) when I see a new type of light I spin my eyes in circles and then I see the refresh going. Street lights will show as a pulse, just like a TV. In fact, a lot of electronics use pulse refreshing, even VCR clocks!
I don't mean to babble about stuff that I don't know of, but try this experience: take a small electronics device with a LED on it (such as your optical mouse) and move it real quick in front of you, looking directly ahead. You'll see flicker. Do the same with say, a cigarette, and you won't see any flicker at all, because fire doesn't have flicker.
Now, as a bummer, my 19" Samsung CRT gets jumpy at anything other than 60Hz, and I can see the 60Hz one! Gota change for a LCD I think.
printf($randomline(sigs.txt) \n "-- "$randomline(authors.txt));
-- myself
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)
Seeing as I can detect 60hz easily it must clearly be a sign of superior intellect
come on, you thought it
A blog I run for the wealth
Flicker seems more perceptible after I've gone running.
Think it's the exercise?
Maybe this depends on the experience. Example: most people have spent their time in from of the TV CRT which used to work at 50Hz (thankfully TVs now do support 100 Hz). So, having this person in front of 60Hz CRT is like giving him/her something extra to what their eyes are used to. For people who spent most of their time using the PC, 60Hz is ancient past and anytime they see it now they go "ungh!!! my brain hurts!!". Read somewhere that in Japan (never been there, sob) the electricity is set at 60Hz, so their fluorescent light is also refreshing at 60Hz. When they come to Europe and end up in an office with fluorescent light they go "argghhh! turn off the strobe light" ie. they see the flicker in our fluorescent lighting (even when it is perfectly set). The whole story has to do with brain more than eyes. Brain is used to certain frequencies and when it gets less it notices it ;-)
its just a matter of being aware of it or not. i never used to see the flicker until my roomate pointed it out to me. now i can even spot monitor flicker at 75hz. i cursed my friend as well, now he can see the 60hz flicker and was forced to invest in a very nice (and very expensive) samsung lcd. but when i first complained about his old crt monitor he had no idea what "flicker" i was talking about.
brainwave frequencies:l r=&safe=off&q= brainwave+frequencies+hz&btnG=Search
f e=off&q= %22specifications%22+%22human+eye%22+fps&btnG=Sear ch
http://www.google.com/search?hl=en&
eye:
http://www.google.com/search?hl=en&lr=&sa
also consider optic nerve, and eye interface. It could be only USB1 and that could be presenting a problem - I suggest firewire iuntil manufacterors stop changing sensors without telling us.
A blog I run for the wealth
Why the adjective "western" there? Chinese chess is not noticably more complex than western (the cannon makes it a bit more strategic, but not so much), and if you're trying to make an east-vs-west comparison other games are more representative of what's played in the far east.
I am trolling
While I can detect the 60Hz monitors, the real headache generators for me was interlacing, even at high refresh rates. Most people around me had no idea what I was talking about but it was clear as day when a monitor was set to interlacing. I would mention it, they would turn that off, and magically, they would have less eye strain, but still not be aware of the difference. Now I just use LCD monitors, and have since 99.
And yes, I'm also one of those people that can hear electronic devices when they are on
Why is the sky blue, anyway?
Even though my screen is running at 60 Hz. Oh... wait, it's a laptop screen. I can notice anything at 75 Hz or less from a great distance. I don't know why this is, but I can tell that for me it's an evolving thing. I wasn't able to spot 60 Hz, but now I can't watch TV without being a humongus distance away. I think the more you're in front of a screen, the more likely you are to notice, because your eyes become more picky... Or it could just be because I'm a teenager and my eyes are still getting a little better.
---- I am certain of only one thing : I know nothing else.
i know that one... it's annoying... I can walk down the hall of a hotel and tell you which TVs are on. I've also walked into conference rooms with large TVs with a dark screen and known they were on. Non of my collegues noticed.
From time to time I hear a high-pitched electrical sound and I wonder what the source is... I still haven't found it and I had my ears checked. For all ranges I had great responses. For one range she said it was classified as "perfect" whatever that means.
I generally tend to run the highest refresh rate supported by the monitor at the given resolution. 60 and 66 Hz are horribly painful at any resolution, but around 85 Hz or so I don't notice any improvement. The difference between 70 Hz and 85 Hz is completely indistinguishable at 2048x1536 until I've been sitting at the monitor for a couple of hours and my eyes begin to hurt :)
The tiredness some people refer to as a symptom of too low refresh rate is really your iris straining to focus on your target. Even if you can't consciously see the individual scans, your iris is trying to react. Reversing your color scheme (i.e. Visual C++ uses an abysmal black on white scheme by default) has almost as much affect as increasing the refresh rate.
And in theory, the oposite becomes true at a certain point... Increasing the refresh rate beyond X will begin to cause more eye strain.
LCDs don't have this problem, but they run at really God awful resolutions and their gamma ramp is very distorted. There's no flickering, because it often takes more than one refresh for a pixel to go completely blank. CRT flicker is replaced by LCD blur, which doesn't really matter for office productivity type apps...
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.
This is quite a succinct explanation of the perceptual differences.
(stolen from DaBum) I am dyslexia of borg - your ass will be laminated.
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.
F X=0:1:9999 F D=2:1 Q:((X>2)&(X#D=0)!((D>X/2)&(X'=1))) I D>(X/2) W:$X>75 ! W X,?$X+5-$l(X) Q
I set my monitor to 70 hz but couldnt stand the hum it started making (others heard it also) and when I swiched back to 60 I saw the flicker, but not for long.
I can tell the difference, it seems brighter/clearer for me.
and I can hear when someone turns on the TV or is channel surfing. Thats why I'm so annoyed when people keep changing the channel... the squeal it makes... its not exactly audable but you almost FEEL it
By reading this, you have given me brief control of your mind.
Flicker rate also is important for film. Normal film runs at 24 frames per second (FPS) and each frame is flashed twice to give a rate of 48 FPS. Doug Trumbull patented the Showscan film format, which runs at 60 FPS. It never caught on, and Showscan went out of business.
% 20It% 20Works.htm
When Trumbull was working on Showscan he actually ran tests where physiological responses were measured during viewing of film at different rates. He ended up at a 60 FPS rate, although I heard that his patents were for film speeds up to 72 FPS.
For more info check out
http://www.barbeefilm.com/showscan%20-%20How
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.
A lot of studies were done in the NRC's anachoic chamber in Ottawa and eventually they decided to gather up a group of "golden ears" who had demonstrated in past studies superior discrimination. What they found was that time and frequency are a trade-off. The best in frequency were worse in time, etc. Someone determined could dig up the study. I last saw it on the internet about three years ago.
I can sometimes tell the difference (staring normally) between 85 and 90Hz, but no higher. Wag a finger in front of the monitor, you can figure out any rate.
I can't see flicker, my monitors are usually at a resolution that makes normal humans claw their eyes out if they look over my shoulder... I should patent that as a security technique ;-)
~~~~~ BigLig2? You mean there's another one of me?
... but it CAN see ME, and it's stabby.
Or rather, I can see it, but I don't really process the fact that I can until the headache sits in. I'm fine with a fixed rez and frequency monitor (typically 1280x1024x85hx), but going through a protracted period of switching, like you'd do with finding optimal video card settings for a video game, gives me one hell of a headache.
Middle of last week I thought I was getting a migraine from the Splenda-laced drink I was enjoying, but it turned out to be Halo- 60hz on a display my brain was used to taking in at 85. Stabby-stabby-stabby!
Can anyone shed some (flicker-free) light on this?
Simple-- YOU are a robot, THEY are not.
YOU are a Cylon, THEY are not. Surprise!
Anakin Simpson: If you're not with me, then you're my enemy--ooh, donuts!
There's probably also a link to asperger's and autism. Sometimes autism is caused by extreme sensitivities to touch, sound, vision, etc, and every autistic person I know can hear low-frequency monitors and see flourescent flicker (even the 120 hz ones look pale and sickly). My girlfriend is a special ed teacher and confirmed with the mostly autistic class, so there's some anecdotal evidence (the school wouldn't allow more natural halogen light for some reason so that experiment couldn't be done unfortunately).
I can see flicker below 75Hz so I run 85Hz on my work crt (I use an LCD at home).
:/
I also have a sensitivy to bright lights. This is why I try to work with the light behind me and have my brightness turned down.
ATM I have a bright light above my desk and it making life impossible, very sore eyes and I've only been at work for 15mins
---- Put Sig here:
I am currently studying Neuroscience and we spent a great deal of time examining the neurons that are used for light perception in the eye. Because of the circuts of neurons in your retina the peripheral vision is actually more sensative to movement and light variations then your central vision. The center of you eye is used for picking up fine detail in slow moving objects and color. This is why a star appears brighter when you see it from the corner of your eye. This is also why moving objects get picked up by your eye easier in your peripheral vision.
Strangely enough, I have issues with other sounds (low sounds in a crowded room), but I'm still doing fine with high pitches. I can hear those annoying squeeky monitors, TV sets, and various other electronic phenomenoa that are caused by crappy capacitors, etc.
I had one drive past me the other day at night- it destroyed my vision for a good full second. I was left with a streak of red LEDs running up and down the side of my view.
If I turned my head- there followed another streak.
I've written the manufacturer and BEGGED them to do anything to crank the refresh up to 120hz.... because it's honestly a hazard.
I'm considering writing the appropriate government agency... but we'll see.... (or in the case of those lights, not see)
I can spot the one-frame bits of brown blobs that are supposed to be used for tracing down where someone handi-cam'd a movie. What I don't understand is why no-one else can see them.
Bah.
A fun trick with CRT monitors is to hold one of those massage vibrators on your head while you look at the screen. The screen starts looking really wavy.
You can test your manliness (probably only works for men) by letting out as low a rumble as you can. If your voice is sufficiently deep you'll see the screen start to flicker or wave severely.
Direct away from face when opening.
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.
i find its usually easier to spot 60hz from across the room. as my eyes move, the 60hz becomes very apparent.
if i'm sitting square in front of a monitor sometimes it'll be 5 minutes before i realize its at 60hz.
Flourescent lights seem to greatly exacerbate this problem for me.
60 - 75 Hz gives me a headache
80 Hz is barely tollerable
85 Hz is okay
90 Hz is so-so
100 Hz is good
I can tell the difference within 60 - 110 Hz with about +/- 5 Hz precision.
The biggest trick the devil pulled was letting lawyers become politicians so they can write the laws.
I have Partial complex seizures as a result of pesticide poisoning, and the 60 hz flicker drives me bonkers at times.
Also the quartz halogen PAR style light bulbs, have a diode in them that blocks one phase of the US 120 volt AC power (giving the bulb DC voltage), and I can see the flicker in those bulbs as well.
Other people can only see it in their peripheral vision.
Interesting you mention that. Retinal anatomy has it so that on the part of your retina that corresponds to the center of your feild of view, there is a great concentration of cone cells called the fovea. This region of cones give you a much stronger visual aquity at the thing your direct gaze is pointed at. On the other side of things, your peripheral vision is much more sensitive to motion, so you're more likely to pick up motion with more sensitivity on your side. What's also cool is that it gives a reason for why kung fu heroes in the movies always pose their heads at an angle before taking on the dozen ninjas; their peripheral vision gives them much more sensitivity for detecting small movements than staring them straight on.
I always thought I could "see" annoying flicker on everyone else's monitor because of my early Amiga days. See, Amiga video is/was synced to TV refresh rates by default, that's why they made such good video editing systems.
:)
It usually wasent too bad, but if you pumped up the resolution, to 200x400 or something crazy, the screen bounced around like it was on springs.
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museumpeace Tuesday March 15, @04:36PM: ...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....
Rods sense light
Cones sense color
OT maybe, but trivia, males have more rods, females have more cones. (No, this is not a 4th grade joke. Look it up!) This is why males tend to have less acute color vision, and females are more prone to nightblindness.
Flicker and degree of sensitivity to same is probably based deeply in evolution. I mean - would you want to walk across a savanah with folks who couldn't register flicker? Ever seen the dog/cat snap to on an invisible (to you) movement? High sensitivity is what makes a better hunter while the rest of us stay at home and make baskets and mats.
Lost in space at an early age. Survived the vacuum. Now rebuilding castle in air.
Finally someone has brought up a subject that has plagued me for years. Up until now I thought I was the only one with this "problem" I used to work security at a hospital and I used to complain to the other guards about the security monitors and the flicker. Unless I was looking directly at the monitor I could see the scan lines rolling down the screen. I would get some weird looks from the other guards when I would mention this. Anyway, as far as CRTs go, If it's set below 85 hz I can not stand to look at it for more than a minute or so. I can even tell a difference between 85 and 100 hz easily. 100 hz seems perfect to me, anything less and I do get eye strain. I think it would be interesting for a University to do some sort of study and try to figure out if it relates to a persons mental abilities or not. IQ, Artistic ability, eye Rx, and other factors would probably play a role. I have noticed that people that have a higher artistic ability or a higher IQ seem to notice this flicker more than those that don't. Maybe the reason in that lies more with observation skills. A person with an artistic ability tends to have better skills at observation by it's very nature while a person with little or no artistic skills seem to have less observation skills. The same is with IQ. A person with a high or above normal IQ tend to be more observant than a person with lower than average IQ. So maybe the mental capacity of the viewer converts into physical (vision) abilities as well. Now with LCDs as others have mentioned are perfect. I can run an LCD at 60hz all day long and not notice one bit of flicker. However, the tech behind LCDs don't really compare as LCDs are more subjective to millisecond rating than refresh. From 25 to 8 milliseconds is the rating of most LCDs with the lower the ms the higher the "speed" of the LCD. As far as conventional TV, I think the reason TV doesn't cause the eyestrain that a monitor does isn't because of the refresh rate but more of the fact that a TV screen is always "moving" How often does a TV station have a stationary picture on the screen? Unless you turn it on a 3 am (when they show the color bars) then 98% of the time the screen is moving. Also in this factor is the resolution. A TV's resolution is far below what a normal person runs their PC screen at. To sum it up, my feelings are the high resolution, stationary movement of a PC screen, factored with no motion blurring when something on a PC screen does move is the major factors causing flicker when viewed. Maybe the people that suffer from flicker sensitivity should start a support group, the AFSV (Assoc of Flicker Sensitive Viewers) or something . I know I would join. To see how "uncommon" the problem is, go into a Best Buy or CompUSA store and ask a sales clerk what the refresh ratings are on a selected CRT. EVERY time I have asked this from a clerk I get a glazed over look and a "uh, maybe the info is on the box" type of response. They look at me as odd when I tell them that to me a high refresh is much more important than a high resolution. Running a monitor at 1600x1200 is pointless if it runs at 70hz.
- Anony-Mous-30
In other words, the paper seems to suggest that being able to see the flicker on a monitor is the result of eye fatigue from long use of computer monitors, and that continued use will only increase the problem. It would be interesting to know if there is an "upper limit" (ie, you can see 60Hz now, but not 75Hz - but will exposure over long periods to 75Hz make it so you eventually see 75Hz and have to move it up another notch?). Now - if all of this is true, think about those "mad gamers" who crank the frequency of their system up several notches...
Now - I am not calling the kettle here - I have used a computer since I was 10 years old and my monitor was a 19 inch TV less than a foot from my face (which might -maybe- be a reason for my myopia - heh) - so I too can see the flicker of a 60Hz display, so I knock it up a bit, especially on higher-res output (ie, I find a 640x480 or 800x600 60Hz screen acceptable - but anything greater and the Hz goes up for me).
Incidentally, some people here mentioned the Amiga and its flicker. I own a couple of Amigas, and a lot of gear - and one of the items I purchased (because at the time a true multi-sync/multi-scan monitor was hella expensive to buy - anyone know where I could get one today?) was a "flicker-fixer" filter - basically a piece of smoked-color plexiglass (which I paid waaay to much for) velcroed over the screen - which eliminated or reduced the flicker on the screen...
So, I wonder if something of a similar nature could be used on a 60Hz display? Or - perhaps wear a pair of sunglasses (which Amigan's also did back in the day)? Basically, I think the reason this worked is similar to what is known as the "Pulfrich Effect". So, perhaps two of these filters (or one large filter covering the screen) would simply delay the flickering of the image, forcing you to see a steady image, which is why this works?
I smell a new research paper here: "Theraputic Application of the Pulfrich Effect in the Reduction of Flicker Fusion Frequency" - just remember to give me a mention in a footnote or something, will ya?
Reason is the Path to God - Anon
I can think of several reasons that only some would perceive monitor flicker. Beyond natural variations in the way the visual system developed, sensory "style" could also come into play.
Many people have developed a "style" of primarily taking visual information from the center of their visual field (the fovea) where we have fine resolution and color vision. Others have a "style" where they integrate additional information from the peripheral vision which has lower resolution and no color perception but is more sensitive to light in general and to change in the image (to detect motion, but flicker will catch it's attention too).
In some cases, people learn after the fact to use the peripoheral vision because of it's sensitivity. Navigators, astronomers, and infantry amongst others will either consciously or unconsciopusly learn the trick of looking to the side of dim objects they need to see. Once you learn the technique, it's actually fairly easy to spot meteors and sattelites for example.
Anyone using that style will be more aware of flicker than others.
In general, the failure to realise that there are natural variations in sensory styles and, for that matter, capabilities has been a problem for product development and ergonomics.
A common form is monitors and televisions that emit a horrible squeel that will drive some people (particularly children) from the room. The only hope they have is that as they age, their hearing will degrade enough that they can tolerate the sound or even cease hearing it.
I run into the same problem with the sense of smell and taste. Apparently people swear that the artificial scents in NEARLY EVERYTHING are "pleasant" or "floral". Meanwhile, to me, many of them (not all) smell slightly worse than old gym socks or dead skunk (and induce the runny nose and nasal constriction any sufficiently bad smell would), even if I like the natural scent it is meant to imitate. If it didn't provoke such an annoying physiological response, the idea of men and women splashing on a cologne named "Roadkill" would be fairly amusing.
It's not just over-sensitivity to smells in general, when I was in chemistry, I had little trouble adjusting to halogens or the dreaded sulpher compounds that never stop bothering many people. Appearently, it's just some difference in 'olfactry spectrum'. It may be just a matter of sensitivity levels, or it could be analogous to people that have an additional primary color in their vision.
It's also interesting that in 40 years, I have never heard the word "corollary" uttered aloud outside of high school and college literature classes. This is despite my association with a broad range of people from numerous nationalities. Many of these people are very highly educated and not all of them are of a technical background. I have rarely if ever seen the word "corollary" in print either. Yet on Slashdot, I see it almost daily.
Isn't that interesting? I'm sure that it says something but, I'm not sure what that something is. I wonder what it means?
After smoking some good weed, I always see the flickering..
I've found the following demo to help people understand what I'm talking about.
Open up a white window (notepad, textedit, whatever) and make it full screen. Wave your hand in front of the monitor. Change the refresh rate to something higher and do it again.
While most people don't notice the flicker, they will become aware of the strobe effect.
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.
An idea i had for a science fair project when i was in middle school was to use a bicycle wheel (the spokes, really) at a carefully controlled velocity and see if not only were people different in the speed in which they percieved no movement of the spokes, but also if moods/body temperature/intoxication changed these rates. Were any metabolism indicators (blood pressure, etc.) linked to the rate?
:) support science in schools!)
Alas, they canceled the science fair that year. Bummer
(the one before that was on 3 methods of generating random number and how random each method was. No one could judge it, because no one knew anything about programming
which varies from ~50-100 hz and interacts with CRT's refresh. What you see is visual "aliasing". A side effect: your brain cannot detect a temporal difference less than a value proportional to the inverse of this refresh rate.
I could be wrong, but I believe that it has a bit to do with the dialation of one's pupils. When your eyes are more dark adjusted , they become slower in their responsiveness.
I used to notice the flicker, but 60Hz is all the monitors can handle. I now can filter it out unless I chose to notice. Hope my eyes don't fall out...
md5sum
d41d8cd98f00b204e9800998ecf8427e
I'm far more sensitive to monitor flicker a couple hours after taking my SSRI medication (serzone). Hrm.
Everyone has a different number of cone neurons, which are responsible for detecting color and detail. This is why flicker is perceived by some and not by others. A higher concentration of cones means you'll see less flicker. The further from the center of the retina (periphery perception), the less concentration of cones. So you'll be more likely to see flicker from your peripheral vision. Every one is different. Celebrate diversity blah blah blah.
I'm not sure that this is exactly the same, but ever since I saw Fight Club, I notice every cigarette burn when reels change. Although, technically, I'm not sure that they change anymore, so much as they signify a splice where two reels were spliced. I think current movies come in multiple wheels and are made into one big reel to avoid the projector switching. Something I noticed on the second Harry Potter movie and have noticed in other movies since, is what I believe is the new movie protection scheme. Throught out the movie a handful of frames, on the order of 3 to 5 frames are marked with a number of black dots. IE, 5 dots on 5 different frames. I've always assumed that this was a copyright protection for bootlegging, but who knows. Just wondering if anyone else has ever noticed this.
"Where's the any key?" - Homer Simpson
The refresh rate of your eyes is known as persistence of vision. Some people have a higher rate than others. You can use an adjustable strobe light to see what your rate is. Different animals have different rates as well. Supposedly a praying mantis has incredibly fast persistence of vision.
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