Digital Camera Shutters

Discussion in 'Digital Photography' started by RD Munger, Aug 20, 2004.

  1. RD Munger

    RD Munger Guest

    Hello everyone.

    I've noticed that digital SLR's have a focal plane shutter similar to film SLR's in front
    of the CCD and digicams do not.

    What is the reason for this? Are there any web links to help explain this technology?

    Thanks to all.

    Robert
     
    RD Munger, Aug 20, 2004
    #1
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  2. RD Munger wrote:
    > Hello everyone.
    >
    > I've noticed that digital SLR's have a focal plane shutter similar to
    > film SLR's in front of the CCD and digicams do not.
    >
    > What is the reason for this? Are there any web links to help explain
    > this technology?
    >
    > Thanks to all.
    >
    > Robert


    Digicams can (and do) use a leaf shutter in the lens - a benefit of not
    needing interchangeable lenses.

    Cheers,
    David
     
    David J Taylor, Aug 20, 2004
    #2
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  3. RD Munger

    Chris Brown Guest

    In article <>,
    RD Munger <> wrote:
    >Hello everyone.
    >
    >I've noticed that digital SLR's have a focal plane shutter similar to
    >film SLR's in front
    >of the CCD and digicams do not.
    >
    >What is the reason for this? Are there any web links to help explain
    >this technology?


    Some compacts have no mechanical shutter at all, using electronic
    shuttering. A DSLR sensor, however, is designed to maximise the sampling
    area, and so needs to be read out in darkness, hence the need for a shutter.

    Some compacts do have a mechanical shutter as well, but it would often be a
    leaf shutter, rather than a focal plane shutter. This makes sense in a
    small-sensor compact For a number of reasons:

    - No issue with an interchangable lens system needing a shutter in each lens.

    - Flash sync at all shutter speeds.

    - The usual disadvantage of leaf shutters, that they are limited to slowing
    speeds, is limited. The short focal lengths used by compact digicams
    means that the diameter of the lens isn't that large, and so you're not
    so constrained by the sheer physical distance you need to cover quickly.

    - Related to the above point, you can reduce costs by combining the leaf
    shutter and aperture blades.
     
    Chris Brown, Aug 20, 2004
    #3
  4. On Fri, 20 Aug 2004 16:01:17 GMT, David J Taylor hath writ:
    > RD Munger wrote:
    >> Hello everyone.
    >>
    >> I've noticed that digital SLR's have a focal plane shutter similar to
    >> film SLR's in front of the CCD and digicams do not.
    >>
    >> What is the reason for this? Are there any web links to help explain
    >> this technology?
    >>
    >> Thanks to all.
    >>
    >> Robert

    >
    > Digicams can (and do) use a leaf shutter in the lens - a benefit of not
    > needing interchangeable lenses.


    My Olde Kodak Retina Reflex III and IV 35MM cameras employ(ed) leaf
    shutters in their interchangeable lenses.
    They were expensive suckers...

    Jonesy
    --
    | Marvin L Jones | jonz | W3DHJ | linux
    | Gunnison, Colorado | @ | Jonesy | OS/2 __
    | 7,703' -- 2,345m | config.com | DM68mn SK
     
    Allodoxaphobia, Aug 20, 2004
    #4
  5. RD Munger

    Ken Scharf Guest

    Chris Brown wrote:
    > In article <>,
    > RD Munger <> wrote:
    >
    >>Hello everyone.
    >>
    >>I've noticed that digital SLR's have a focal plane shutter similar to
    >>film SLR's in front
    >>of the CCD and digicams do not.
    >>
    >>What is the reason for this? Are there any web links to help explain
    >>this technology?

    >
    >
    > Some compacts have no mechanical shutter at all, using electronic
    > shuttering. A DSLR sensor, however, is designed to maximise the sampling
    > area, and so needs to be read out in darkness, hence the need for a shutter.
    >
    > Some compacts do have a mechanical shutter as well, but it would often be a
    > leaf shutter, rather than a focal plane shutter. This makes sense in a
    > small-sensor compact For a number of reasons:
    >
    > - No issue with an interchangable lens system needing a shutter in each lens.
    >
    > - Flash sync at all shutter speeds.
    >
    > - The usual disadvantage of leaf shutters, that they are limited to slowing
    > speeds, is limited. The short focal lengths used by compact digicams
    > means that the diameter of the lens isn't that large, and so you're not
    > so constrained by the sheer physical distance you need to cover quickly.
    >
    > - Related to the above point, you can reduce costs by combining the leaf
    > shutter and aperture blades.

    Leaf shutters are limited in speed. To obtain shutter speeds as high as
    1/1000 sec or higher a focal plane shutter is required. Leaf shutters
    that double as the iris also can limit the maximum f stop that the
    camera can be set to. I don't think many digicams stop down smaller
    than F8, though there may be other reasons for this. Focal plane
    shutters also have a maximum flash sync speed, usually 1/250 sec or so.
    This is because above this speed the shutter operates in the moving slit
    mode rather than the fully open mode.
    No reason (other than cost) why a digicam couldn't have two shutters
    to get the advantages of both.
     
    Ken Scharf, Aug 21, 2004
    #5
  6. RD Munger

    Alan Browne Guest

    RD Munger wrote:

    > Hello everyone.
    >
    > I've noticed that digital SLR's have a focal plane shutter similar to film SLR's in front
    > of the CCD and digicams do not.
    >
    > What is the reason for this? Are there any web links to help explain this technology?


    As others have said, for the sensor to work optimally, it first
    needs to measure its own noise in darkeness. So a mechanical
    blocker is needed (v. the potential to simply electronically
    shutter in the sensor).

    Leaf shutters in the lens could be used, but interchangeable
    lenses for 35mm SLR's do not have leaf shutters (there are a very
    few examples of 35mm lenses that have leaf shutters. System
    optimization has put the shutter in the right place for 35mm, the
    FP).

    FP shutters are well known, have been in massive production for
    decades and achieve very high speeds (1/12,000 sec in the Maxxum
    9, 1/8,000 in other high end (S)SLRs including the 20D.)

    Cheers,
    Alan.


    --
    -- rec.photo.equipment.35mm user resource:
    -- http://www.aliasimages.com/rpe35mmur.htm
    -- e-meil: there's no such thing as a FreeLunch.--
     
    Alan Browne, Aug 23, 2004
    #6
  7. RD Munger

    Ron Baird Guest

    Greetings Jonesy,

    I can appreciate your interest and question.

    I do not have all details here at my disposal, but I believe the CX, DX, and
    LS model cameras that Kodak offers use an electromechnical shutter/aperture.
    This combination allows the computers in the camera to accurately select the
    correct exposure based on some pretty sophisticated math. There are many
    things that work in concert that determine the right exposure, and hence the
    settings in question. Truth is that a simple and easy to use camera is only
    simple on the outside, as the technology that enables the simplicity is
    quite sophisticated.

    The camera in your experience (Retina - I had a few), worked by you setting
    the ISO, lens aperture, and shutter speed, as they worked independently.
    The film had latitude that would allow for some variation in exposure. So,
    when you pressed the shutter release, the mirror would flip up, the aperture
    open, and the film curtain actuate. With digital the correct exposure is
    automated by the computer in the camera and the shutter and aperture set
    accordingly. You may have an aperture of F/4.65 and a shutter of 1/387th
    seconds. So, when you press the shutter release the aperture of the camera
    would open to F/4.65 then close again after 1/387th of a second. You would
    end up with a correct exposure.

    Different than the earlier type of settings, and you are right.

    Talk to you soon,

    Ron Baird
    Eastman Kodak Company





    "Allodoxaphobia" <> wrote in message
    news:...
    > On Fri, 20 Aug 2004 16:01:17 GMT, David J Taylor hath writ:
    > > RD Munger wrote:
    > >> Hello everyone.
    > >>
    > >> I've noticed that digital SLR's have a focal plane shutter similar to
    > >> film SLR's in front of the CCD and digicams do not.
    > >>
    > >> What is the reason for this? Are there any web links to help explain
    > >> this technology?
    > >>
    > >> Thanks to all.
    > >>
    > >> Robert

    > >
    > > Digicams can (and do) use a leaf shutter in the lens - a benefit of not
    > > needing interchangeable lenses.

    >
    > My Olde Kodak Retina Reflex III and IV 35MM cameras employ(ed) leaf
    > shutters in their interchangeable lenses.
    > They were expensive suckers...
    >
    > Jonesy
    > --
    > | Marvin L Jones | jonz | W3DHJ | linux
    > | Gunnison, Colorado | @ | Jonesy | OS/2 __
    > | 7,703' -- 2,345m | config.com | DM68mn SK
     
    Ron Baird, Aug 23, 2004
    #7
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