From: Todd Eacrett (email suppressed)
Date: Thu Nov 01 2007 - 11:07:58 PDT
Pat,
I'm all for the mythic, the poetic and even the mythopoetic but I
don't have time for fairytales pretending to be facts. Yes, your
textbook was wrong. Film studies and historians have perpetuated
a falsehood for a century after science disproved it.
It appears this is finally changing -- the 9th edition of Kawin &
Mast has an updated section on pov which admits it has nothing to
do with the perception of movement in motion pictures.
Pov does exist, just not in the sense you're arguing. This is from a
neuroscientist at Kodak's research division:
"There are two kinds of persistence of vision. The first - negative
(e.g. staring for a while at a red spot on a white background causes
you too see a cyan spot on a blank sheet for a while afterwards) -
is due to fatigue in the retina and is a simple physiological effect.
The second � positive � is the eye/brain hanging on to the image
after the image has disappeared. This latter effect causes us to be
unaware of blinking most of the time, but has nothing to do with
seeing continuous motion at the cinema. If we stored the previous
image in our minds it would overlap with the next one and cause
the effect of motion blur."
Best,
Todd
----- Original Message -----
From: Flick Harrison <email suppressed>
Date: Wednesday, October 31, 2007 11:10 am
Subject: Re: how much of what we see is black?
> Todd!
>
> Are you suggesting that myths are less useful for artists than
> science?
> ;-0
>
> Well, I was taught about persistence of vision straight out of the
> textbook in 1994 at film school, which is reason enough to be
> skeptical. Ha ha.
>
> But it seems like the Andersons spend a lot more time explaining
> different types and implications of motion perception than
> "debunking" the myth of persistence of vision. You'll notice I
> didn't actually conflate the two.
>
> P.o.v. is a physiological concept. Not psychological.
>
> I have no idea if it's a scientifically correct explanation of the
> failure to perceive black between film images, though I have yet
to
>
> hear a better explanation.
>
> But that paper you linked to does nothing to debunk it! It could
> be,
> as Herbert suggests, that we are simply ignoring the black -
> Occam's
> razor leans this way - but that's not proof.
>
> (the unattributed stuff in Herbert about after-images is worth
more
>
> checking out, though it doesn't disprove p.o.v. by suggesting
> another
> phenomena takes place later).
>
> Good reading though, and I appreciate the challenge to my long-
held
>
> ideas.
>
> The reference to Munsterberg is especially, hilariously weak.
> Perhaps
> his original articles are much more substantial.
>
> When I see a scientific paper that says, "no part of the vision
> system remains stimulated for any measurable length of time
after
> the
> last photon hits it; retinal nerves reset themselves to neutral
> within less than 21 milliseconds (1/48th s)" then I'll believe it.
> Proszynski isn't a neurologist; he made projectors.
>
> If p.o.v. is the wrong term (flicker fusion?), or scientists can
> divide it up into multiple concepts, then ok.
>
> I would enjoy a p.o.v. wikipedia update coming from this
discussion.
>
> I said: the illusion of continuous image is a factor of p.o.v. (or
> whatever physiology calls it) Motion-illusion is a separate thing.
>
> You can get a motion-illusion from a flipbook, though you'll still
> see, faintly, the flipping pages themselves. They aren't moving
> fast
> enough to completely disappear. At below 18 fps projection,
you'll
> get motion-illusion but you'll see flickers. In fact, the illusion
> of
> motion can happen even at incredibly slow shutter speeds, with
long
>
> periods of black in between (though not SMOOTH motion). But a
half
> second of black will definitely register on your brain; 1/48th
> second
> of black won't.
>
> Film Journals aren't exactly the place for hard science (and
> neither
> is film school, apparently). Especially when the writer of this
> essay
> seems to be attacking "19th century" (i.e. assumed outdated)
> Marxist
> and Psychoanalytic film theory through this back channel, in
> addition
> to DB's critique of his objectives.
>
> "From our present perspective it seems reasonable to ask why
film
> scholars have been content for most of the twentieth century
with a
>
> nineteenth century explanation of the apparent motion in motion
> pictures. But then, we could just as well ask why they have
> contented themselves with a nineteenth century explanation of
mind
> (Freud's psychoanalytic model) or a nineteenth century
explanation
> of
> society (Marxism). The answer is not readily apparent. "
>
> Seriously: why shouldn't a 19th century explanation be fine and
> dandy
> for a 19th century phenomenon like Cinema? My bike works fine
and
> it's essentially a 19th-century design.
>
> (And here we are using a 20th-century-style usenet discussion
group
>
> instead of a 21st-century virtual world, har har).
>
> They call p.o.v. "a totally inadequate explanation of the illusion
> of
> motion in the cinema." Not an incorrect explanation for flicker
> fusion, i.e. the illusion of continuous image.
>
> There's plenty more bad logic in the next couple paragraphs.
>
> Their interpretation of Roget's work in their original "Myth of
> Persistence of Vision" essay
>
> http://www.uca.edu/org/ccsmi/ccsmi/classicwork/Myth1.htm
>
> skips over the whole 1/48th-of-a-second-blackness issue,
because
> they
> conflate "after-images" left by a very bright light, which stay in
> one place in your eye and can last for some time, versus the
medium-
>
> bright overall image which *might* persist only for 1/48th of a
> second. You can move your head around while watching a movie,
they
> seem to argue (though they are using the bicycle-spoke example
> rather
> than cinema itself), and the movie still seems to be continuous,
> rather than becoming jerky and blocky as the sequential after-
> images
> fail to line up. Therefore no afterimages exist.
>
> But this obviously assumes you are moving your head around
fast
> enough to cause a significant difference - more difference than,
> say,
> an object moving quickly across a giant cinema screen image -
> within
> 1/48th of a second. Heads don't move that fast. And if they did,
> it
> would no doubt alter the perception of the image, assuming the
info
>
> from your inner-ear fluid wouldn't clear up the confusion.
>
> "Clearly, a simple fusion of a succession of images would not
> result
> in the perception of motion. It would result in the perception of
> one
> composite, still image. "
>
> This is a straw man because no one is suggesting that ALL the
> images
> persist forever. It's sequential. One image persists only long
> enough
> for the next image to pop up.
>
> The whole argument of the Andersons is based on refuting
> persistence-
> of-vision by substituting "illusion of motion" halfway through the
> argument: There is no such thing as persistence of vision
because
> the
> illusion of motion cannot be entirely explained by it. There is no
>
> dog in my house because there is plenty of dog food left.
>
> Over and over, they argue that "processing" of the image doesn't
> take
> place in the retina, therefore no p.o.v. exists.
>
> I've never heard anyone suggest that processing takes place in
the
> retina (unless it's like film processing, ie. converting visible
> light into photo-electric brain-readable information). The p.o.v
> idea
> is that the retina retains the image and sends it on to the brain
> as
> if it were still happening. The brain processes it and that's where
>
> the illusion of motion takes place.
>
> I could write more but bla bla bla bla bla.
>
> * FLICK's WEBSITE:
> http://www.flickharrison.com
> * FACEBOOK
> http://www.facebook.com/profile.php?id=860700553
> * BLOG / NEWS:
> http://zeroforconduct.blogspot.com
> * MYSPACE:
> http://myspace.com/flickharrison
>
>
> On 30-Oct-07, at 1:59 PM, Todd Eacrett wrote:
>
> > The myth of persistence of vision was first debunked 30 years
ago:
> >
> > http://www.uca.edu/org/ccsmi/ccsmi/classicwork/Myth%
> > 20Revisited.htm
> >
> >
> > Todd Eacrett
> >
> >
> > ----- Original Message -----
> > From: Flick Harrison <email suppressed>
> > Date: Tuesday, October 30, 2007 1:28 pm
> > Subject: Re: how much of what we see is black?
> >
> >> Hate to be a splitter.
> >>
> >> We don't actually "see" any blackness at all. From our point
of
> >> view, there is no blackness.
> >>
> >> Aside from the witty comment on here that you can't see
> > blackness
> >> (it
> >> is the absence of an image, so it's more like not-seeing).
> >>
> >> Persistence of Vision is the phenomena wherein your optic
nerve
> > (or
> >>
> >> whatever) takes time to "reset" i.e. cool down and stop
> >> transmitting
> >> the last image you saw.
> >>
> >> Frame rates which create the optical illusion of continuous
> >> movement
> >> are using this phenomena.
> >>
> >> The image stays in your optic nerve while the shutter closes,
> >> advances the frame, then re-opens just in time for your optic
> > nerve
> >>
> >> to absorb a new image.
> >>
> >> Your eye / mind never notices the blackness because it's not
fast
> >> enough to see it.
> >>
> >> I.o.w., your eye is fooled into thinking there is no darkness.
The
> >>
> >> darkness is too short for you eye's mechanism to register.
> >>
> >> It;s not like the optical illusion of a bunch of dots becoming
a
> >> straight line as you pull back. That is simply perceptual /
mental
> >>
> >> illusion, at least until you get back so far that the dots fall
> >> below
> >> the resolution of your eyeballs.
> >>
> >> It's more like an optical override.
> >>
> >> To be clear - continuous motion on screen is an optical
illusion,
> >> created by a series of still pictures. Continuous brightness on
> >> screen is a neurological illusion, not an optical one - though
> >> that's
> >> splitting optic nerve-hairs.
> >>
> >>
> >> * FLICK's WEBSITE:
> >> http://www.flickharrison.com
> >> * FACEBOOK
> >> http://www.facebook.com/profile.php?id=860700553
> >> * BLOG / NEWS:
> >> http://zeroforconduct.blogspot.com
> >> * MYSPACE:
> >> http://myspace.com/flickharrison
> >>
> >>
> >> On 30-Oct-07, at 6:53 AM, Yoel Meranda wrote:
> >>
> >>> A question I'm curious about...
> >>>
> >>> When a film projector is running, what is the percentage of
> > time the
> >>> light is interrupted by the shutter? In other words, what
> > percentage
> >>> of what we see is darkness?
> >>>
> >>> I realize that this question will have different answers for
each
> >>
> >>> projector...
> >>>
> >>> I am mostly curious about 35mm projectors but any clue
on
> > any other
> >>> projector would be great. Even guesses would be fine if no
one
> > has
> >>> concrete answers.
> >>>
> >>> Thanks,
> >>>
> >>> yoel
> >>>
> >>>
> >>>
> >
_________________________________________________________________
> > _
> >>> For info on FrameWorks, contact Pip Chodorov at
> > <email suppressed>.
> >>
> >>
> >>
> >>
> >
_________________________________________________________________
> > _
> >> For info on FrameWorks, contact Pip Chodorov at
> > <email suppressed>.
> >>
> >>
> >
> >
> >
_________________________________________________________________
_
> > For info on FrameWorks, contact Pip Chodorov at
<email suppressed>.
>
>
>
>
_________________________________________________________________
_
> For info on FrameWorks, contact Pip Chodorov at
<email suppressed>.
>
>
__________________________________________________________________
For info on FrameWorks, contact Pip Chodorov at <email suppressed>.