How fast is the human eye?

[Karel Bata]

• David Fincher used that subliminal flash thing again in Fight Club, having an image of Brad Pitt somewhere in shot for a frame. On first viewing I missed most of them, though a couple of times I thought I saw something. My girlfriend, sitting next to me, kept saying (and to my intense irritation) "Look! there it is again!"
  "What?"
  "I don't know."
  On second viewing I knew what I was looking for and saw each one clearly.
   
  Walter, when you say that the theory of 'persistence of vision' is dead, you appear only to replace it with a theory of 'persistence of perception'. I don't think that clears anything up at all.

...we are led to suspect that since the processing of real motion is initiated directly by the magno system, then most likely the processing of short-range apparent motion and the motion of motion pictures is also initiated by the magno system, and that long range apparent motion is perhaps processed less directly -- perhaps through reentrant connections from other areas, as happens in the perception of illusory contours. Further research is needed to clarify this matter.

 
As to 'How fast is the human eye?' Jeez. I can see a strobe flash at 1/10000th of a second. Meanwhile, sometimes, a fluorescent may look fine viewed full on, but I can clearly see the flicker out of the corner of my eye, so I know it'll blow soon. I think that babies, and many of our pets, see the whole urban world flickering around them. But they quickly learn to tune it out. Turn a CRT TV upside down so the scan goes the wrong way - you'll likely see the flicker for a while until you adjust.
 
But how much do ever 'see' anyway? Look over (and then back here straight away) at a bookshelf close to you. Go on, do it. Now don't move your eyes from this text. What was the third book from the right (or left)? Did you ever really 'see' it? We are so familiar with these massive holes in our perception of the world we don't think anything of them.
 
Even those whose job it is to 'see' things keep getting it wrong: Scientists study 4,000 tennis points and find 80% of umpire 'out' calls are 'in'
 

 
Or get your head around this! One of my favorite theorists: There is no stream of consciousness She writes about 'Stream of Vision'.
 
As a slight aside, I came across this the other day: The same color illusion which has interesting implications for us.
 
 
So, uh, just how long was that piece of string? <_<
 
String? What string? :o

[Stuart Brereton]

many of our pets, see the whole urban world flickering around them.

 

There is evidence to suggest that Cats can see the scan line on a CRT. It's one explanation for why they sometimes appear to be watching the tube...

[Walter Graff]

There is evidence to suggest that Cats can see the scan line on a CRT. It's one explanation for why they sometimes appear to be watching the tube...

 

Yes cats have shorter neural paths in their eyes so instead of seeing a pristine picture, they see more flicking of a TV screen with images from that screen mixed in. Sort of like shooting off speed at a TV set just real off speed. Cat videos prove that cats do indeed see the picture though as they will swat at elements in the video and sometimes run around to the back of the set to catch what ran away. But more importantly cats use smell and sound more than they do sight. Sight to them is about movement. One reason cats don't look at themselves in a mirror. I saw a documentary that said cats usually recognize your smell and hear your voice which is more the key as to why they approach you over seeing you first.

[Paul Bruening]

Yes cats have shorter neural paths in their eyes so instead of seeing a pristine picture, they see more flicking of a TV screen with images from that screen mixed in. Sort of like shooting off speed at a TV set just real off speed. Cat videos prove that cats do indeed see the picture though as they will swat at elements in the video and sometimes run around to the back of the set to catch what ran away. But more importantly cats use smell and sound more than they do sight. Sight to them is about movement. One reason cats don't look at themselves in a mirror. I saw a documentary that said cats usually recognize your smell and hear your voice which is more the key as to why they approach you over seeing you first.

 

Dogs can't look up.

[Walter Graff]

Dogs can't look up.

 

 

Guess you don't have a dog. Yes dogs can look up. They have binocular vision so their eye muscles are not as elastic as your for vertical moment but indeed the eyes move vertically in the socket. Since they have binocular vision dogs tend to use the head to aim the eyes rather than the soceekts but that does not mean htey can't look up. Mine does it all the time.

[Paul Bruening]

But... I saw it in a movie. Dogs can't look up.

[Karel Bata]

Dogs can't look up.

How do they bark at the moon then? :huh:

 

• 
   
  Stare at the center cross for at least 30 seconds
  

[Walter Graff]

But... I saw it in a movie. Dogs can't look up.

 

I saw Spider Man swing on a thread in a movie too. :) Dogs have mostly binocular vision so do not have much in terms of eye movement but they do have vertical and horizontal capabilities. If I hold my dogs head and someone moves a biscuit in front of her both up and to the side, my dogs eyes track so sorry to spoil the myth. Owls have completely binocular vision and tubular eye balls so can not move their eyes at all and must use the head to do all looking.

 

Notice the attached picture. The dogs head is shifted upward slightly and that the eyes too have vertical movement as the whites below illustrate. It is not full movement in terms of degree like a human but definitely moving the eyes vertically.

 

[John Allen]

But Walter that picture doesn't really prove anything, cause a good editor could pull that off. Maybe you were just kidding though, because I do recall you saying that you should believe everything that you see on the internet. So I would think that you would feel the same way about movies, right? lol I for one have never seen a dog move his eyes up, but I don't really care a whole lot if they do or don't so it's not like I've watched them very intensively.

[Walter Graff]

But Walter that picture doesn't really prove anything, cause a good editor could pull that off. Maybe you were just kidding though, because I do recall you saying that you should believe everything that you see on the internet. So I would think that you would feel the same way about movies, right? lol I for one have never seen a dog move his eyes up, but I don't really care a whole lot if they do or don't so it's not like I've watched them very intensively.

 

That's okay John. As a dog companion who can make his dog move his eyes up, I can tell you first hand that they do. As I said, it's not as far as you can move yours. But then again, try to move yours up and notice how useless it is to do more than 10 degrees and hence, like a dog, easier to move your head than your eyes. And the picture is untouched.

 

Fun stuff from dog companions http://en.wikipedia.org/wiki/Wikipedia:Ref...dogs_look_up.3F

[John Allen]

Yeah I know. I was just teasing. ;) I'm sure they can move their eyes at least a little. lol

[Mike Lary]

When watching Se7en, did you notice the 2 second flash frame? If so, could you see what it was or did you have to go back and pause to see what the image was?

Watching it in the theater, I don't remember seeing those two frames. Watching it again after being told where they were, the image's subject was clear, but I couldn't see enough detail to answer the question 'was that a current image or one from a character's memory?'.

 

I already knew the context and what the image would be, so I was just waiting and focusing much harder than I would have if I hadn't been told to look for it. My brain couldn't draw the image quick enough for me to properly identify it without visual memory that I acquired by watching what preceded that scene.

[John Sprung]

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.

There are two separate issues here, flicker fusion, and the illusion of motion.

 

Flicker is the easier one. The rate needed to make a series of light pulses appear continuous varies depending on the brightness of the light, whether you see it in central or peripheral vision, and on the individual observer.

 

Theaters generally use two blade shutters in film projectors, which results in 48 light flashes per second. Without film, they're supposed (SMPTE standard) to put 16 foot Lamberts on the screen. That's not very bright, because at higher illuminations, the rate required for flicker fusion is higher. There are three blade/72 flash per second projectors for that purpose.

 

Your peripheral vision is more sensitive to flicker. If you look at an ordinary NTSC TV set, you don't see flicker. But if you turn to look at something nearby, putting the TV near the edge of your field of view, you'll see it flickering even at 60 Hz.

 

The illusion of motion depends on the sample rate, the amount of undersampling, and the individual observer. The illusion starts working for most people around 14 - 16 frames per second, and works quite well at 24, provided that the motion isn't too fast, nor the shutter angle too small. Because of the need to mechanically pull down film, we've become accustomed to substantial undersampling, which is what a 180 degree shutter gives us. Undersampling causes skipping or strobing, and is also the reason for spoked wheels appearing to turn backwards. Undersample too far, and the result is sort of an unpleasantly fast slide show rather than a movie.

 

There are some rare individuals who seem to process vision much faster than most. They see all movies as a succession of individual frames. All time great boxing champion Joe Louis (1914 - 1981) was able to read the label on a 78 RPM phonograph record while it was playing. No doubt that's a useful attribute in the ring. ;-)

 

 

 

 

-- J.S.

[Paul Bruening]

Maybe, it's cows.

[David Rakoczy]

There are some rare individuals who seem to process vision much faster than most. They see all movies as a succession of individual frames.

 

-- J.S.

 

Hi John.

 

I often experience this myself... especially when shooting. I often see each and every frame being captured... kinda like stop motion at 24fps... well, exactly like. The first time I experienced this I had to really contain myself during a long take as I couldn't believe what I was seeing... now I am used to it and enjoy it!

[John Sprung]

I often experience this myself...

 

Interesting -- If you ever get access to an old time turntable that'll go 78 RPM, see if you can do the Joe Louis reading trick.

 

 

 

 

-- J.S.

[David Rakoczy]

Interesting -- If you ever get access to an old time turntable that'll go 78 RPM, see if you can do the Joe Louis reading trick.

 

 

 

 

-- J.S.

 

Back on jobs where I was just operating and the Director would ask me, because on many jobs monitors were purposely left at the rental house, what I thought ... I could tell him/ her confidently "every frame was beautiful" and mean it :lol:

[Karel Bata]

Can you tell the future too?

 

 

 

 

 

 

always worth asking...

[Karel Bata]

David, seriously, what do you see when you look at this:

• 
   
  Stare at the center cross for at least 30 seconds
  

You should see 3 illusions:

1) At first you see them wink out in sequence, but quickly as they wink out they are replaced by a blob of blue, but as you stare for longer...

2) this turns into a turquoise blob that travels clockwise, until

3) it eats up all the other blobs (pacman style) until only the turquoise blob is left in a gray rectangle.

 

Illusions 1 and 2 are retinal, while 3 goes on in the brain and is known as 'change blindness' and has been studied using brief blank flashes between pictures, with image flicker, during cuts in movies and even during eye blinks. In one study an experimenter approached a pedestrian to ask for directions. While they talked, two men rudely carried a door between them. The first experimenter grabbed the back of the door and the person who had been carrying it let go and took over the conversation. Only half of the pedestrians noticed the substitution!

 

I think you'd be among the half that would always spot it.

 

So, do you see all three illusions? And is anyone else here missing any? Is anyone in fact seeing an incomplete circle of lilac blobs moving anti-clockwise (I get that for brief snatches)?

[Walter Graff]

I'd love to see some sort of citation for the Joe Lewis "story". Greats in time often have mythology surrounding them. Let's see. Joe Lewis was a fighter. One of the top 100 punchers ever. What better a story than to say, Joe was so fast he could read the label of a record spinning. Sort of like saying a basketball great could take the penny off the top of a backboard. :) While there are slight variables to some of the elements in how humans see (women see more colors, etc), it is not enough that someone is a superhuman and can freeze time to see frames. There is physiological condition called dichoptic motion transparency where one eye sends signals to the brain at a slightly different speed than the other and the brain can inerpoate images diferently than normal same-speed binolcular vision, but outside of that, I don't know any science studied that shows anyone can freeze individual images, let alone see them. If that was the case, it owuld be hard ot watch TV as you'd see retrace. There is a form of photographic memory where the brain can create multiple still images of a moment in time (sort of the prinicple of how photogrophic memory works). Perhaps that is more what is being referred to here.

[David Rakoczy]

Almost immediately #3.. one turquoise dot. :blink:

 

The first time I experienced this was while operating Silk Stalkings on the USA Network. Stu Seagal would not allow monitors on set and had his Directors and DP rely solely on the Operator.. me. The Camera was a Panavision Elaine. This is about 3 or 4 months in on a 7 month season.. operating 5 days a week.. 8-13 pages a day. One day after lunch I was relaxing watching a take when all of a sudden I started seeing (or perceiving.. hard to tell) every frame. I started to giggle as I couldn't believe what I was seeing.. every frame.. every movement.. it was like time slowing down.. and capturing each individual frame.. in 'real' time. It was very strange. Since then, I am able to make it happen just by relaxing.. and can get into that space while the shutter is spinning and see them all... one at a time. Remember those pictures that were all just a jumble of etched lines.. but once you stared at it long enough all of a sudden you realize you are viewing a 3D picture.. and the more you do it the easier it is to get into that space where you see it... same thing with this. I have discussed this with other DP/ Operators and haven't found anyone who sees this, tho, no doubt others do...

[John Sprung]

You should see 3 illusions:

1) At first you see them wink out in sequence, but quickly as they wink out they are replaced by a blob of blue, but as you stare for longer...

2) this turns into a turquoise blob that travels clockwise, until

3) it eats up all the other blobs (pacman style) until only the turquoise blob is left in a gray rectangle.

 

Here's how it worked for me:

 

1) At first, they wink out to be replaced by a faint blue, very soon the blue grows stronger, becoming....

 

2) The turquoise blob as described. The original purple blobs after a while get a bluish halo that meanders with slight head movement.

 

3) Eating up some of the original blobs happens much later, and comes and goes. Some pop back on while others go away. Eventually most of them are gone, but any slight head movement and they come back again.

 

4) I get a little bit of a headache.

 

 

 

-- J.S.

[David Rakoczy]

What Walter is talking about is also why people experience 'Deja-Vu'. Tho I personally experience 'Vuja-De' more often... you know... that strange feeling you get when you feel that none of this has happened to you before :huh:

[Karel Bata]

Walter, according to one report of a test done Muhammad Ali apparently had the fastest reaction time ever recorded! You think about what fast reaction times evolved for and what boxers do and the cost of failure, and it's hardly surprising.

 

David, so you can switch it off? I was wondering if it drove you nuts sometimes! :lol: Sounds cool.

 

Sorry to give yo a headache John. :huh:

 

" that none of this has happened to you before" Don't you mean... ?

[Chris Keth]

You haven't seen 'Se7en'? Shame on you, Chris....

 

Nope. :unsure: I picked up a handful of sand and some grains fell through my fingers. This thread did make me bump it up my netflix list, though.