When Electronic shutter "open"/"close"?

Discussion in 'Digital Photography' started by =?iso-8859-1?Q?mark=5Fdigital=A9?=, Mar 5, 2006.

  1. Strong light makes some people wink or blink. What I don't understand is how
    the camera can capture this reaction considering it still takes a moment for
    the motor nerves to respond to the stimuli. Nerve messages only travel about
    35 miles an hour. One would think that by the time you see the flash it
    actually reached you a moment before you realized it and the shutter opened
    an closed prior to your blinking. No?


    mark_
     
    =?iso-8859-1?Q?mark=5Fdigital=A9?=, Mar 5, 2006
    #1
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  2. =?iso-8859-1?Q?mark=5Fdigital=A9?=

    Dave Cohen Guest

    "mark_digital©" <> wrote in message
    news:...
    > Strong light makes some people wink or blink. What I don't understand is
    > how the camera can capture this reaction considering it still takes a
    > moment for the motor nerves to respond to the stimuli. Nerve messages only
    > travel about 35 miles an hour. One would think that by the time you see
    > the flash it actually reached you a moment before you realized it and the
    > shutter opened an closed prior to your blinking. No?
    >
    >
    > mark_

    The auto exposure uses a pre-flash on p&s models.
    Dave Cohen
     
    Dave Cohen, Mar 5, 2006
    #2
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  3. =?iso-8859-1?Q?mark=5Fdigital=A9?=

    Tesco News Guest

    "mark_digital©" <> wrote in message
    news:...
    > Strong light makes some people wink or blink. What I don't understand is
    > how the camera can capture this reaction considering it still takes a
    > moment for the motor nerves to respond to the stimuli. Nerve messages only
    > travel about 35 miles an hour. One would think that by the time you see
    > the flash it actually reached you a moment before you realized it and the
    > shutter opened an closed prior to your blinking. No?
    >
    >
    > mark_



    Hi.

    Like so many other things in Photography, don't bother about why it happens,
    it just does. It is more important to learn how to get round it.

    It did so well before Digital Cameras or Flashguns with Pre-flashes,
    (whether for Red Eye or Exposure).

    If you are working, one to one, with someone who is prone to the "Blinking"
    problem, get them to tightly close their eyes, then just as you are about to
    fire the shutter, ask them to open their eyes.

    You should be able to get a photo, with eyes.

    Roy G
     
    Tesco News, Mar 5, 2006
    #3
  4. "Tesco News" <> wrote in message
    news:nHEOf.25621$...
    > "mark_digital©" <> wrote in message
    > news:...
    >> Strong light makes some people wink or blink. What I don't understand is
    >> how the camera can capture this reaction considering it still takes a
    >> moment for the motor nerves to respond to the stimuli. Nerve messages
    >> only travel about 35 miles an hour. One would think that by the time you
    >> see the flash it actually reached you a moment before you realized it and
    >> the shutter opened an closed prior to your blinking. No?
    >>
    >>
    >> mark_

    >
    >
    > Hi.
    >
    > Like so many other things in Photography, don't bother about why it
    > happens, it just does. It is more important to learn how to get round it.
    >
    > It did so well before Digital Cameras or Flashguns with Pre-flashes,
    > (whether for Red Eye or Exposure).
    >
    > If you are working, one to one, with someone who is prone to the
    > "Blinking" problem, get them to tightly close their eyes, then just as you
    > are about to fire the shutter, ask them to open their eyes.
    >
    > You should be able to get a photo, with eyes.
    >
    > Roy G
    >
    >
    >

    You mean REAL TIGHT, like so tight it takes a moment to focus after you open
    your eyes? Sounds like it might work.
     
    =?iso-8859-1?Q?mark=5Fdigital=A9?=, Mar 5, 2006
    #4
  5. =?iso-8859-1?Q?mark=5Fdigital=A9?=

    wilt Guest

    Lots of people, when taking a photo, outloud count down (or up)
    "3...2...1... <click>" That gives many subjects the verbal cue to
    unconsciously blink...Really! If you shoot a little bit early or you
    delay a bit, in an unpredictable manner, your subject will not be able
    to anticipate the actual firing and you have a lowered probability of
    catching them in the blinking.

    In group photos I prefer to have my camera on tripod perfectly
    pre-framed, then take the remote in my hand which is kind of down by my
    side and less clearly visible to subjects, then standing next to my
    camera I am looking directly at the group and giving some directions,
    and I will often trigger the camera without verbal warning! If the
    flash has a battery pack which provides very rapid recycling, I often
    will shot TWO shots one right after the other, because often the
    subjects relax a moment after the first shot is taken and you have much
    less 'put on' expressions!
     
    wilt, Mar 5, 2006
    #5
  6. =?iso-8859-1?Q?mark=5Fdigital=A9?=

    Tesco News Guest

    "mark_digital©" <> wrote in message
    news:...
    >
    > "Tesco News" <> wrote in message
    > news:nHEOf.25621$...
    >> "mark_digital©" <> wrote in message
    >> news:...
    >>> Strong light makes some people wink or blink. What I don't understand is
    >>> how the camera can capture this reaction considering it still takes a
    >>> moment for the motor nerves to respond to the stimuli. Nerve messages
    >>> only travel about 35 miles an hour. One would think that by the time you
    >>> see the flash it actually reached you a moment before you realized it
    >>> and the shutter opened an closed prior to your blinking. No?
    >>>
    >>>
    >>> mark_

    >>
    >>
    >> Hi.
    >>
    >> Like so many other things in Photography, don't bother about why it
    >> happens, it just does. It is more important to learn how to get round it.
    >>
    >> It did so well before Digital Cameras or Flashguns with Pre-flashes,
    >> (whether for Red Eye or Exposure).
    >>
    >> If you are working, one to one, with someone who is prone to the
    >> "Blinking" problem, get them to tightly close their eyes, then just as
    >> you are about to fire the shutter, ask them to open their eyes.
    >>
    >> You should be able to get a photo, with eyes.
    >>
    >> Roy G
    >>
    >>
    >>

    > You mean REAL TIGHT, like so tight it takes a moment to focus after you
    > open your eyes? Sounds like it might work.


    Hi.

    Yes I do, and keep them closed for a few minutes.

    When open, it is not so much the lack of focus, it has more to do with the
    muscles being in a relaxed state after having been tensed up for a while.

    Having said that, given some time, a "Blinker" will gradually stop being
    nervous about the impending flash, and will be able to control their eyes
    much better.

    When shooting a portrait sesssion with Film, I never used to expect there to
    be any good pictures in the first 36, if the subject was a "Blinker".

    Roy G
     
    Tesco News, Mar 5, 2006
    #6
  7. =?iso-8859-1?Q?mark=5Fdigital=A9?=

    george Guest

    "mark_digital©" <> wrote in message
    news:...
    > Strong light makes some people wink or blink. What I don't understand is
    > how the camera can capture this reaction considering it still takes a
    > moment for the motor nerves to respond to the stimuli. Nerve messages only
    > travel about 35 miles an hour. One would think that by the time you see
    > the flash it actually reached you a moment before you realized it and the
    > shutter opened an closed prior to your blinking. No?
    >
    >
    > mark_


    I am a bit curious as to where you got your data on the nerve responses
    traveling at 35 mph??? (I don't know what the real number is, but would
    expect it to be much higher because: 1) it is an involuntary response; and,
    2) electrical signals (which a nerve signal is) travels at the speed of
    light when in a vacuum...obviously, it would be slower in your body, how
    much slower I haven't a clue.) But, even at 35 mph that is 51.33 fps and
    how far does it have to travel from eye to brain? Six inches? That'd be
    around 9.74 ms assuming your number is right and my guess on how far is
    right...this would imply that with shutter speeds faster than 1/100 sec you
    wouldn't have the problem...but we know that isn't right (from experience),
    so I think you're a bit low on nerve impulse speed.
     
    george, Mar 6, 2006
    #7
  8. "george" <> writes:

    > "mark_digital©" <> wrote in message
    > news:...
    >> Strong light makes some people wink or blink. What I don't understand is
    >> how the camera can capture this reaction considering it still takes a
    >> moment for the motor nerves to respond to the stimuli. Nerve messages only
    >> travel about 35 miles an hour. One would think that by the time you see
    >> the flash it actually reached you a moment before you realized it and the
    >> shutter opened an closed prior to your blinking. No?
    >>
    >>
    >> mark_

    >
    > I am a bit curious as to where you got your data on the nerve responses
    > traveling at 35 mph??? (I don't know what the real number is, but would
    > expect it to be much higher because: 1) it is an involuntary response; and,
    > 2) electrical signals (which a nerve signal is) travels at the speed of
    > light when in a vacuum...


    Umm.. electrical signals don't travel at all in a vacuum. In a good
    conductor, like copper or silver, they travel at about 95% of the
    speed of light.

    > obviously, it would be slower in your body, how much slower I
    > haven't a clue.)


    Quite a bit slower, actually, but I don't have any exact numbers.

    > But, even at 35 mph that is 51.33 fps and how far does it have to
    > travel from eye to brain? Six inches? That'd be around 9.74 ms
    > assuming your number is right and my guess on how far is
    > right...this would imply that with shutter speeds faster than 1/100
    > sec you wouldn't have the problem...but we know that isn't right
    > (from experience), so I think you're a bit low on nerve impulse
    > speed.


    It's the preflash that triggers the blink, so the your calculations
    don't mean a lot without knowing the time between preflash and
    exposure.

    --
    Måns Rullgård
     
    =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?=, Mar 6, 2006
    #8
  9. Måns Rullgård wrote:
    >
    > It's the preflash that triggers the blink, so the your calculations
    > don't mean a lot without knowing the time between preflash and
    > exposure.



    Nice concept, but the phenom has been around longer than flashes
    utilizing preflash. And what's your source?

    --
    John McWilliams
     
    John McWilliams, Mar 6, 2006
    #9
  10. george wrote:
    > "mark_digital©" <> wrote in message
    > news:...
    >> Strong light makes some people wink or blink. What I don't understand is
    >> how the camera can capture this reaction considering it still takes a
    >> moment for the motor nerves to respond to the stimuli. Nerve messages only
    >> travel about 35 miles an hour. One would think that by the time you see
    >> the flash it actually reached you a moment before you realized it and the
    >> shutter opened an closed prior to your blinking. No?
    >>
    >>
    >> mark_

    >
    > I am a bit curious as to where you got your data on the nerve responses
    > traveling at 35 mph??? (I don't know what the real number is, but would
    > expect it to be much higher because: 1) it is an involuntary response; and,
    > 2) electrical signals (which a nerve signal is) travels at the speed of
    > light when in a vacuum...obviously, it would be slower in your body, how
    > much slower I haven't a clue.) But, even at 35 mph that is 51.33 fps and
    > how far does it have to travel from eye to brain? Six inches? That'd be
    > around 9.74 ms assuming your number is right and my guess on how far is
    > right...this would imply that with shutter speeds faster than 1/100 sec you
    > wouldn't have the problem...but we know that isn't right (from experience),
    > so I think you're a bit low on nerve impulse speed.


    if there were one big nerve cell that did the whole job.
    however, there are nerve to nerve junctions
    which are chemical in nature,
    and do not happen at the speed of light.

    >
    >
     
    bob crownfield, Mar 6, 2006
    #10
  11. =?iso-8859-1?Q?mark=5Fdigital=A9?= <> writes:
    >Strong light makes some people wink or blink. What I don't understand is how
    >the camera can capture this reaction considering it still takes a moment for
    >the motor nerves to respond to the stimuli.


    If your camera was totally silent and fired the flash only once, the
    subject would not have time to blink.

    But many P&S digital cameras fire the flash twice: once to measure flash
    exposure and once to take the actual picture. I once measured the delay
    on a particular digital camera as more than 100 ms. That's enough time
    for people to blink in response to the first flash. (Apparently more
    recent cameras have reduced this delay).

    Blinking happened in the days of film cameras too. There, it was due to
    people hearing the noise of the mirror and shutter mechanism and
    blinking in anticipation of the flash they expected to follow.

    Dave
     
    Dave Martindale, Mar 8, 2006
    #11
  12. =?iso-8859-1?Q?mark=5Fdigital=A9?=

    Alan Meyer Guest

    george wrote:
    > ...
    > I am a bit curious as to where you got your data on the nerve responses
    > traveling at 35 mph??? (I don't know what the real number is, but would
    > expect it to be much higher because: 1) it is an involuntary response; and,
    > 2) electrical signals (which a nerve signal is) travels at the speed of
    > light when in a vacuum...obviously, it would be slower in your body, how
    > much slower I haven't a clue.)
    > ...


    Conduction of signals through nerves is an electro-chemical
    reaction rather than a purely electrical current like what we
    see in an electrical wire.

    There is an electric potential difference (a difference in
    electrical charge) between the inside and the outside of
    the nerve cell membrane. Stimulation of the nerve causes
    channels in the membrane to open up and charged ions
    to flow through, eliminating the potential difference and
    stimulating a chemical reaction that is transmitted on to
    the next region of the cell. At the end of the cell (the
    synapse), chemicals called neurotransmitters are released
    which conduct the signal to adjacent nerve cells.

    All of this is amazingly fast for a bio-chemical life process
    and it's much faster in some animals than others (never
    try wrestling with a leopard or a giant squid :), but it's still
    orders of magnitude slower than electrical conduction.

    Alan
     
    Alan Meyer, Mar 8, 2006
    #12
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