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How fast is the human eye?


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#1 Daniel Porto

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Posted 23 January 2009 - 08:30 PM

How fast is the human eye? What is the minimum amount of frames needed for us to visibly see something?

Does it have something to do with age? When I watched Se7en as a kid I did not notice the 2 frame cut of the wife at the end (even though I had watched it 3 times), however at the age of 17 when I re-watched it, I noticed the cut.

Is this simply only because I am consciously looking for things like that in an image (because I have a passion in the production side of film) and thus normal audience members don't notice it consciously but possibly sub-consciously?

Possibly because of the intense emotion in the scene I was so into the movie that any cut that was made did not register in my mind, thus I did not notice the cut (even though it cuts from a yellow sort of colored image to one that is quite over exposed and white).

Share your thoughts...
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#2 Edgar Dubrovskiy

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Posted 23 January 2009 - 08:39 PM

What second frame???
Did I miss something? Four times...
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#3 Steve McBride

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Posted 23 January 2009 - 08:52 PM

There's no such thing. A frame is a part of a piece of film that is captured to be playedback in a string of similar images to form a visual. The human eye sees constantly, there is no other "frame" that we see, we see continually through the same "frame" all the time.

When you're younger, you're not trained to pick out certain things when you are conscious, so you miss them. As you grow older and become educated and learn more (especially now when you are into the technical developings of film) and notice the small details that you missed out when you were a child.

Now, I could be wrong, but this is the way I see it. I guess you could argue with what I have said when you do something like wave your hand infront of an object, you see the movement of where your hand was previously. But is there any way to prove that you're actually seeing where your hand was, or is it just your brain processing the fact that before your hand was where it stopped, it had to cross the space between where it started, so it fills in the missing "information" with what "should" be there (motion blur).
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#4 Edgar Dubrovskiy

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Posted 23 January 2009 - 09:06 PM

There's no such thing. A frame is a part of a piece of film that is captured to be playedback in a string of similar images to form a visual. The human eye sees constantly, there is no other "frame" that we see, we see continually through the same "frame" all the time.

When you're younger, you're not trained to pick out certain things when you are conscious, so you miss them. As you grow older and become educated and learn more (especially now when you are into the technical developings of film) and notice the small details that you missed out when you were a child.

Now, I could be wrong, but this is the way I see it. I guess you could argue with what I have said when you do something like wave your hand infront of an object, you see the movement of where your hand was previously. But is there any way to prove that you're actually seeing where your hand was, or is it just your brain processing the fact that before your hand was where it stopped, it had to cross the space between where it started, so it fills in the missing "information" with what "should" be there (motion blur).

Hm. What about the 'persistence of vision'?
We don't see the flicker in cinemas, do we?

Can't say that I agree on this one.
I do agree that the eye sees 'one frame'.
But the trick is - the brain doesn't.
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#5 Steve McBride

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Posted 23 January 2009 - 09:24 PM

I guess I expanded on the question and got into the brain when the question was only the eye, then again I'm just theorizing/ making stuff up as I go, haha.

I'd never heard of the persistance of vision before now, but it's really interesting.
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#6 David Mullen ASC

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Posted 23 January 2009 - 09:28 PM

The eye, when it is open, is constantly receiving light and producing various level of "signal" to the brain -- it's not a series of discreet samples at regular rates. You could say that shooting with a movie camera is a form of sampling, breaking something continuous and analog into a series of separate units.

In terms of how the brain processes that information, it depends on a lot of factors, like our concentration. Our minds tend to "edit" out redundant information. Water Murch described this experiment in "Blink of an Eye" -- the first time we scan a room with our eyes in a long "pan", we tend to keep our eyes open -- but when we do it a second time, we tend to blink in the middle because we've already seen the room so we feel relaxed enough to skip around a bit with our eye/brain.

The only way to create this feeling of continuous "sampling" is to shoot and project at higher frame rates. I believe Doug Trumbull tested this when he created the Showscan process and found that any improvement above 60 fps was minimal, but 60 fps was dramatically more effective than 24 fps. But he said that viewers say improvements even at 100 fps and higher.
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#7 Chris Keth

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Posted 23 January 2009 - 09:28 PM

Our eye's minimum "shutter speed" is about 1/14th of a second. That's what we were taught in photo technology classes at RIT, anyway. Below that, pretty much everyone would see it as flicker. Above that, some people see flicker up until 17 or 18fps. Above that everyone sees it as continuous motion.

Edited by Chris Keth, 23 January 2009 - 09:31 PM.

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#8 David Mullen ASC

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Posted 23 January 2009 - 09:31 PM

I think the real question is what is the fastest strobe speed necessary for a viewer to see it as a continuous light. That would sort of tell you the maximum frame rate needed to look continuous.

I mean, look at TV sets -- we can see the difference between a 60 Hz refresh rate and a 120 Hz refresh rate.
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#9 Chris Keth

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Posted 23 January 2009 - 09:43 PM

I think the real question is what is the fastest strobe speed necessary for a viewer to see it as a continuous light. That would sort of tell you the maximum frame rate needed to look continuous.

I mean, look at TV sets -- we can see the difference between a 60 Hz refresh rate and a 120 Hz refresh rate.


That's what my number above are. We did a few tests with the class to demonstrate it. The prof had a piece of clear film in a projector with continuously variable speed and a FPS readout. He started it at 1fps and slowly increased it. We were to note when we stopped seeing any black. It was between 14-17fps for most people. I think I was 16 or 17 fps.

That was a great class. I learned a lot about my own eyes and preferences in the context of the test sample of the class.

Edited by Chris Keth, 23 January 2009 - 09:45 PM.

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#10 Mike Lary

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Posted 23 January 2009 - 11:29 PM

When I was studying motion graphics we were told that anything below 14fps would be noticeably jerky. I'm sure the threshold varies for individuals based on genetic makeup and age as well as external factors that influence the operation of the eyes and the brain, such as caffeine, diet, sleep, and stress.

It makes perfect sense that you see more details in a film after watching it several times. Your brain processes image information and tries to relate it to memory. If you've seen a series of images repeatedly it's part of your memory so your brain knows what's coming and it's redrawing it for you automatically. Details that might have gone by in previous viewings are easier to pick up on (like vignetting during an intense battle scene in The Thin Red Line that I don't think I saw till the third viewing). The same is true when you're reading a familiar book. If you study film or literature, though, you're training your brain to be more perceptive, to look more at the structure of what you're viewing/reading instead of just interpreting the story. And if you know something is coming, like the demonic frames in The Exorcist or the porn snippets in Fight Club, it's going to be much more noticeable to you.

Persistence of Vision, aside from being taught in film studies, is largely dismissed. According to modern science, there is no frame rate in the eye or in the brain. It's a much more complex process than catching reflected light and flipping it right side up.
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#11 Brian Dzyak

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Posted 24 January 2009 - 12:30 AM

http://www.journalof...11/article.aspx

Brief subjective durations contract with repetition
Vani Pariyadath

Department of Neuroscience, Baylor College of Medicine, Houston, TX, USA

[home] [e-mail]
David M. Eagleman

Department of Neuroscience and Department of Psychiatry, Baylor College of Medicine, Houston, TX, USA

[home] [e-mail]
Abstract

Neural responses to a repeated stimulus typically diminish, an effect known as repetition suppression. We here demonstrate what appear to be parallel effects of repetition on subjective duration, even when stimuli are presented too rapidly for explicit temporal judgments. When a brief visual stimulus (e.g., a letter, word, object, or face) was serially flashed in different locations, several stimuli appeared to be present simultaneously due to persistence of vision—we term this the Proliferation Effect. Critically, fewer stimuli were perceived to be simultaneously present when the same stimulus was flashed repeatedly than when a different stimulus was used for each flash, indicating that persistence of vision (and hence subjective duration) shrinks for predictable stimuli. These short-timescale experiments demonstrate that subjective durations are computed at a preconscious and implicit level of processing, thereby changing the temporal interpretation of visual scenes. Further, these findings suggest a new, instant diagnostic test for deficits in repetition suppression, such as those found in schizophrenia.


History
Received May 24, 2008; published December 22, 2008


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#12 A. Whitehouse

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Posted 24 January 2009 - 01:08 AM

Some what related;
There was a scandal (probably too strong a word) last year at the Australian Music awards where, during the televised event, some of the sponsors logos were flashed onto the screen in an integrated graphic for two or three frames. Some viewers noticed (including my friend an editor) and complained as this is against broadcast regulations.
After 6 months the broadcast regulator in Australia deemed the 3 frame ones legal but less than that illegal as it was below perception and considered subliminal, now some were 1 frame long and I believe that it should be argued that if any standard exists it should be above the absolute minimum for broadcast, I mean any less than a frame or two frames is obviously impossible unless it is flickered into a field or something.
Ive seen these promos and I didn't catch it the first time even though it was pointed out to me, even the legal ones, the only reason they exist is to act subliminally and I thought the broadcast regulators were pretty weak in response.
Examples are available on the ABC website for the show "Mediawatch" who did a couple of stories on the situation with the ARIAS, little was done about it because action is largely dictated by the number of complaints. Difficult for something which is below awareness for most people. I wonder if it sold more Chuppa-Chupps and KFC?
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#13 Brian Dzyak

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Posted 24 January 2009 - 01:45 AM

Some what related;
There was a scandal (probably too strong a word) last year at the Australian Music awards where, during the televised event, some of the sponsors logos were flashed onto the screen in an integrated graphic for two or three frames. Some viewers noticed (including my friend an editor) and complained as this is against broadcast regulations.
After 6 months the broadcast regulator in Australia deemed the 3 frame ones legal but less than that illegal as it was below perception and considered subliminal, now some were 1 frame long and I believe that it should be argued that if any standard exists it should be above the absolute minimum for broadcast, I mean any less than a frame or two frames is obviously impossible unless it is flickered into a field or something.
Ive seen these promos and I didn't catch it the first time even though it was pointed out to me, even the legal ones, the only reason they exist is to act subliminally and I thought the broadcast regulators were pretty weak in response.
Examples are available on the ABC website for the show "Mediawatch" who did a couple of stories on the situation with the ARIAS, little was done about it because action is largely dictated by the number of complaints. Difficult for something which is below awareness for most people. I wonder if it sold more Chuppa-Chupps and KFC?



Speak of the devil.....

http://www.bizjourna...19/daily17.html

Tuesday, January 20, 2009, 9:37am CST | Modified: Wednesday, January 21, 2009, 8:28am
Miller High Life will have 1-second Super Bowl ad

MillerCoors said Tuesday that it will premier a one-second ad for its Miller High Life brand during the Super Bowl broadcast Feb. 1.

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“Miller High Life is all about high quality and great value, so it wouldn’t make sense for this brand to pay $3 million for a 30-second ad,” said High Life senior brand manager Kevin Oglesby, in a press release. “Just like our consumers, High Life strives to make smart choices. One second should be plenty of time to remind viewers that Miller High Life is common sense in a bottle.”

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#14 Daniel Porto

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Posted 24 January 2009 - 02:29 AM

What second frame???
Did I miss something? Four times...


You certainly did!
Watched closely at 3:06! (Please do not watch this clip if you haven't seen the movie... it will ruin it!)

http://www.youtube.c...feature=related

The editor on the commentary stated that it was a 2-frame cut. He also explains that he believes we can see a 1-frame cut, and that our ability to notice these cuts is determined by a range of factors.

I do agree that the eye sees 'one frame'.
But the trick is - the brain doesn't.

This is the sort of answer I was looking for... does that mean that one frame is too fast to be even noticed sub-consciously?

Mike Lary makes good points that a range of factors externally and internally (and also how are brain relates to memory) effect our ability to notice sharp cuts like in Se7en.

Perhaps I should re-phrase my question. In the style of the cut that I just explained in Se7en, what would be the shortest amount of frames in which a fully concentrated viewer will say...
1. "What was that flash??" i.e. they see a change in image but not sure what they saw (even then will their brain register sub-conciously what the image was?) [this happened to me after my 4th viewing at age 17, then I had rewind and pause to see what the image was].
2. "I just saw a flash of his wife" i.e. What is the minimum many frames needed for the human brain to recognize the image it just saw.


Obviously what I am asking will depend upon viewer to viewer but I would like to hear your thoughts and opinions.
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#15 Daniel Porto

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Posted 24 January 2009 - 02:37 AM

Some what related;
There was a scandal (probably too strong a word) last year at the Australian Music awards where, during the televised event, some of the sponsors logos were flashed onto the screen in an integrated graphic for two or three frames. Some viewers noticed (including my friend an editor) and complained as this is against broadcast regulations.
After 6 months the broadcast regulator in Australia deemed the 3 frame ones legal but less than that illegal as it was below perception and considered subliminal, now some were 1 frame long and I believe that it should be argued that if any standard exists it should be above the absolute minimum for broadcast, I mean any less than a frame or two frames is obviously impossible unless it is flickered into a field or something.
Ive seen these promos and I didn't catch it the first time even though it was pointed out to me, even the legal ones, the only reason they exist is to act subliminally and I thought the broadcast regulators were pretty weak in response.
Examples are available on the ABC website for the show "Mediawatch" who did a couple of stories on the situation with the ARIAS, little was done about it because action is largely dictated by the number of complaints. Difficult for something which is below awareness for most people. I wonder if it sold more Chuppa-Chupps and KFC?


I was told by an advertising consultant once that 'subliminal advertising' was once used at cinemas (obviously other forms also) and that they would flash frames of popcorn and drinks, then show a commercial for the cinemas candy bar, in the hope that they will go and spend some money!

It would be interesting to find out what the methods were used to set the law that anything 3 frames or above is not subliminal advertising.
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#16 David Auner aac

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Posted 24 January 2009 - 04:35 AM

Can't say that I agree on this one.
I do agree that the eye sees 'one frame'.
But the trick is - the brain doesn't.


I have read into the process seeing quite a bit a couple of years ago. One major thing in almost every text on the topic was this: the eye doesn't see at all! It's only the brain that sees. There is no visible image in the eye, it only delivers sensor data that the brain converts into what we see.

Regards, Dave
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#17 Edgar Dubrovskiy

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Posted 24 January 2009 - 06:21 AM

You certainly did!
Watched closely at 3:06! (Please do not watch this clip if you haven't seen the movie... it will ruin it!)


Ah, yes!
I saw it - completely forgot about this.

Fincher, bloody Hell.
And a week ago he told in QA session there is no wife's head :)
Cheeky.
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#18 Marc Roessler

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Posted 24 January 2009 - 06:32 AM

Speed of the eye seems to be training issue, but some of it seems to be genetic or something..

Some people will be unable to see the difference between a 1-chip-DLP and a 3-chip-DLP projector, for example.
Yet to others it just jumps at you, especially when you move the eyes. Some won't see a difference, even if you tell them what to look for.

There is also a visible difference between TI DLP (which uses pulse width modulation for varying the light level, since DLP can only do "on" or "off") and the Sony SRX technology (steady light levels), despite you aren't able to see it on a conscious level. Same goes for 50/60Hz flourescent - you can't see it it flicker consciously, but you notice a difference. Now how fast is the eye?

Oh, another thing. You know the CAP codes burned in 35mm prints for tracking pirated copies filmed from theater screens? They are orange dot patterns, similar to the dots on dices. I will notice them all the time, and I even can tell what pattern is was. Many of my friends don't really notice even when you tell whem when they occur (in some cases they are printed every few seconds), others notice when you tell them but can't tell the pattern, and others don't see anything at all.

Highly interesting. Really makes you wonder how others around you perceieve the world...

Edited by Marc Roessler, 24 January 2009 - 06:33 AM.

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#19 Daniel Smith

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Posted 24 January 2009 - 07:54 AM

Kinda unrelated but... if you noticed the cut I think the editor done a bad job. Unless it intended otherwise.
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#20 Walter Graff

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Posted 24 January 2009 - 09:54 AM

The eye, when it is open, is constantly receiving light and producing various level of "signal" to the brain -- it's not a series of discreet samples at regular rates. You could say that shooting with a movie camera is a form of sampling, breaking something continuous and analog into a series of separate units.

In terms of how the brain processes that information, it depends on a lot of factors, like our concentration. Our minds tend to "edit" out redundant information. Water Murch described this experiment in "Blink of an Eye" -- the first time we scan a room with our eyes in a long "pan", we tend to keep our eyes open -- but when we do it a second time, we tend to blink in the middle because we've already seen the room so we feel relaxed enough to skip around a bit with our eye/brain.

The only way to create this feeling of continuous "sampling" is to shoot and project at higher frame rates. I believe Doug Trumbull tested this when he created the Showscan process and found that any improvement above 60 fps was minimal, but 60 fps was dramatically more effective than 24 fps. But he said that viewers say improvements even at 100 fps and higher.


The only addition I would make is that while the eye is always open, the speed at with nerve impulses excited by light in the eye refresh is about 1/25th of a second. Since various ganglion are constantly refreshing, this does not stop you from seeing contiguous motion but does cause phenomenon’s of the eye in certain situations. Basically TV is an electronic version mimicking how the eye sees, so a lot of questions about the eye are as simple as looking at how TV works (e.g. how contrast is so much more important than color, etc). Some folks talk about how we see blurring effects and how that must mean we have a limit to how many FPS we see. This is incorrect. The reason we see blurring is because our brain has a filter for information. We only allow ourselves to process so much. In evolutionary terms this is due to our need to see and what we needed to see and how important it was to see. An eagle for instance can spot a mouse on the ground from a mile in the air. How? It has a blur filter that shows it images more like high speed film with the mouse movement looking like sharp fast motion in fast still images, what some call on-off vision. The eagle developed the need for this. Cat's too have this high speed filter that allows them to see motion in sharp detail. In fact if you stand still you will notice a cat eventually has to scan to see you with it's eye back and forth or it actually can’t see you. But humans never needed to see sharp fast motion as we learned to pick berries more than hunt prey so our brains developed the blur filter that allows as much information as we need to see, then blurs everything else. So when you drive in a car at 65mph everything moves by you in a blur. If you were an eagle, everything would be in sharp pulses so you'd see constant 'frames' of sharp image presented as on-off-on-off, albeit in black and white as such birds have no need for color. And the evolutionary berry picking is also attributed to why we see so little blue and why women see colors 30% more than men.

Research shows that the eye can make motion of individual frames with a thresh hold of about 11 fps. 18fps is generally considered the threshold for film to look like fluid motion. That is the center of the eye. it's the edges of our field of view that are more susceptible to flicker. Try looking up at the ceiling in a theater during a movie and you'll see that the screen does indeed flicker. After 18fps it's all about what you need to see that determines how fast you need to present it. There is no limit. Video games (like Nanosaur I played with my kid today) plays at frame rate between 180fps and 200fps. Fast frame rates like this are needed in order for the eye to properly see (really more the fringe vision than the center vision) all of the motion and depth perception seem fluid and not choppy in the entire field of view.

As for persistence of vision, IT IS A MYTH. Let me say it again, PERSISTANCE OF VISION IS A MYTH perpetuated for 100 years in textbooks and proven wrong through research on how the eye sees and what parts of the brain process it and how. I was even involved with such research two years ago involving brain imaging during normal vision experiments. Even though it has been shown to be wrong, it still is a persuasive myth still found in textbooks and on websites. Read more here:

http://www.uca.edu/o...20Revisited.htm

Of note: While I can not give details, we are using the change in frame rates on 'screens' as ‘eye catchers’ right now on certain public displays in the US. We shuffle frame rates of the monitors presentation so that out of the corner of your eye as you walk by, your brain is triggered to look. Then when you focus on the display, all looks fine and you see what we are selling. The variable frame rate caught your reptilian brains need to hunt prey and triggers you to look. Good 21st century technique using the million year old brain as it has been discovered that a certain frequency of strobing causes a primative area of the brain to light up and forces all concious thought to focus on this strobe.
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