DoF preview

Discussion in 'Digital Photography' started by Faiser, Oct 24, 2003.

  1. Faiser

    Faiser Guest

    Hi,

    Been lurking here for some time, and I'm trying to decide on my first
    prosumer camera. It's great to see how much knowledge is in this group.

    I was wondering if the depth of field can also be previewed on an slr-like
    camera, such as Dimage A1, F717 and the like.
    The D300 has a DoF preview button. How can the aperture size/DoF be
    controlled and previewed on those with EVF?

    What is aperture anyway for the mechanical part - I mean I understand
    aperture size indicates how much the lens is open or closed, but what
    happens inside the lens, could it be compared with a valve or something??

    fwiw, I'm an amateur seeking to purchase a camera only for hobby purposes,
    including some model photography. Trying to decide here between D300,
    Dimage A1 or wait for F828.. but I'm in no hurry because searching for the
    'best' camera, reading reviews and comments over and over is already half of
    the fun!

    Thanks
     
    Faiser, Oct 24, 2003
    #1
    1. Advertising

  2. Faiser

    Todd Walker Guest

    On Fri, 24 Oct 2003 15:08:52 GMT, "Faiser" <>
    wrote:

    >Hi,
    >
    >Been lurking here for some time, and I'm trying to decide on my first
    >prosumer camera. It's great to see how much knowledge is in this group.
    >
    >I was wondering if the depth of field can also be previewed on an slr-like
    >camera, such as Dimage A1, F717 and the like.
    >The D300 has a DoF preview button. How can the aperture size/DoF be
    >controlled and previewed on those with EVF?


    On most cameras that use an EVF, they actually stop down the aperture
    in preview mode (when you are looking at the live picture on the EVF)
    so you can see the DOF at all times. Be aware that the small sensors
    in "prosumer" cameras have quite large DOF even at large apertures.

    >What is aperture anyway for the mechanical part - I mean I understand
    >aperture size indicates how much the lens is open or closed, but what
    >happens inside the lens, could it be compared with a valve or something??


    The aperture is a circular mechanism with multiple blades that open
    and close. There is a picture on this page, though not a very good
    one:

    http://www.kent.k12.wa.us/staff/trobinso/physicspages/PhysOf99/Cam-Atkins/thecamera.html

    Scroll down to the "Aperture" section about halfway down.

    >fwiw, I'm an amateur seeking to purchase a camera only for hobby purposes,
    >including some model photography. Trying to decide here between D300,
    >Dimage A1 or wait for F828.. but I'm in no hurry because searching for the
    >'best' camera, reading reviews and comments over and over is already half of
    >the fun!


    Good luck in your quest. It can be fun but after a while it can just
    get downright frustrating :)

    ________________________
    Todd Walker
    http://www.toddwalker.net
    Canon 10D
    http://www.toddwalker.net/canon10d
    ________________________
     
    Todd Walker, Oct 24, 2003
    #2
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  3. Faiser

    Tony Spadaro Guest

    There can be no dof preview on any camera where the viewfinder image is not
    from the actual lens. If the EVF is through the taking lens dof preview
    should work - but some camreas may not have it.
    The aperture is like a valve -- for amount of light. Each full stop lets
    in half as much light as the one below --- f4 is half the light of f2.8,
    etc.
    There is an article on using dof preview here:
    http://www.chapelhillnoir.com/mani/techs/mmtechs.html
    --
    http://www.chapelhillnoir.com
    home of The Camera-ist's Manifesto
    The Improved Links Pages are at
    http://www.chapelhillnoir.com/links/mlinks00.html
    A sample chapter from my novel "Haight-Ashbury" is at
    http://www.chapelhillnoir.com/writ/hait/hatitl.html
    "Faiser" <> wrote in message
    news:8gbmb.3562634$...
    > Hi,
    >
    > Been lurking here for some time, and I'm trying to decide on my first
    > prosumer camera. It's great to see how much knowledge is in this group.
    >
    > I was wondering if the depth of field can also be previewed on an slr-like
    > camera, such as Dimage A1, F717 and the like.
    > The D300 has a DoF preview button. How can the aperture size/DoF be
    > controlled and previewed on those with EVF?
    >
    > What is aperture anyway for the mechanical part - I mean I understand
    > aperture size indicates how much the lens is open or closed, but what
    > happens inside the lens, could it be compared with a valve or something??
    >
    > fwiw, I'm an amateur seeking to purchase a camera only for hobby purposes,
    > including some model photography. Trying to decide here between D300,
    > Dimage A1 or wait for F828.. but I'm in no hurry because searching for the
    > 'best' camera, reading reviews and comments over and over is already half

    of
    > the fun!
    >
    > Thanks
    >
    >
     
    Tony Spadaro, Oct 24, 2003
    #3
  4. Faiser

    Faiser Guest

    Thanks for that.

    Strange you know, that picture of the aperture mechanism makes believe that
    at closed aperture the image is also cropped to a small circle in the center
    before reaching the film/ccd.

    got me puzzled here..

    Cheers

    "Todd Walker" <> wrote in message
    news:...
    > On Fri, 24 Oct 2003 15:08:52 GMT, "Faiser" <>
    > wrote:
    >
    > >Hi,
    > >
    > >Been lurking here for some time, and I'm trying to decide on my first
    > >prosumer camera. It's great to see how much knowledge is in this group.
    > >
    > >I was wondering if the depth of field can also be previewed on an

    slr-like
    > >camera, such as Dimage A1, F717 and the like.
    > >The D300 has a DoF preview button. How can the aperture size/DoF be
    > >controlled and previewed on those with EVF?

    >
    > On most cameras that use an EVF, they actually stop down the aperture
    > in preview mode (when you are looking at the live picture on the EVF)
    > so you can see the DOF at all times. Be aware that the small sensors
    > in "prosumer" cameras have quite large DOF even at large apertures.
    >
    > >What is aperture anyway for the mechanical part - I mean I understand
    > >aperture size indicates how much the lens is open or closed, but what
    > >happens inside the lens, could it be compared with a valve or something??

    >
    > The aperture is a circular mechanism with multiple blades that open
    > and close. There is a picture on this page, though not a very good
    > one:
    >
    >

    http://www.kent.k12.wa.us/staff/trobinso/physicspages/PhysOf99/Cam-Atkins/thecamera.html
    >
    > Scroll down to the "Aperture" section about halfway down.
    >
    > >fwiw, I'm an amateur seeking to purchase a camera only for hobby

    purposes,
    > >including some model photography. Trying to decide here between D300,
    > >Dimage A1 or wait for F828.. but I'm in no hurry because searching for

    the
    > >'best' camera, reading reviews and comments over and over is already half

    of
    > >the fun!

    >
    > Good luck in your quest. It can be fun but after a while it can just
    > get downright frustrating :)
    >
    > ________________________
    > Todd Walker
    > http://www.toddwalker.net
    > Canon 10D
    > http://www.toddwalker.net/canon10d
    > ________________________
     
    Faiser, Oct 25, 2003
    #4
  5. Faiser

    Faiser Guest

    I see.
    So does anybody know if the Minolta DimageA1 actually has Depth of Field
    preview? It's one of those features that is never mentionned in the
    reviews/tech specs.

    "Tony Spadaro" <> wrote in message
    news:XKgmb.2974$...
    > There can be no dof preview on any camera where the viewfinder image is

    not
    > from the actual lens. If the EVF is through the taking lens dof preview
    > should work - but some camreas may not have it.
    > The aperture is like a valve -- for amount of light. Each full stop

    lets
    > in half as much light as the one below --- f4 is half the light of f2.8,
    > etc.
    > There is an article on using dof preview here:
    > http://www.chapelhillnoir.com/mani/techs/mmtechs.html
    > --
    > http://www.chapelhillnoir.com
    > home of The Camera-ist's Manifesto
    > The Improved Links Pages are at
    > http://www.chapelhillnoir.com/links/mlinks00.html
    > A sample chapter from my novel "Haight-Ashbury" is at
    > http://www.chapelhillnoir.com/writ/hait/hatitl.html
    > "Faiser" <> wrote in message
    > news:8gbmb.3562634$...
    > > Hi,
    > >
    > > Been lurking here for some time, and I'm trying to decide on my first
    > > prosumer camera. It's great to see how much knowledge is in this group.
    > >
    > > I was wondering if the depth of field can also be previewed on an

    slr-like
    > > camera, such as Dimage A1, F717 and the like.
    > > The D300 has a DoF preview button. How can the aperture size/DoF be
    > > controlled and previewed on those with EVF?
    > >
    > > What is aperture anyway for the mechanical part - I mean I understand
    > > aperture size indicates how much the lens is open or closed, but what
    > > happens inside the lens, could it be compared with a valve or

    something??
    > >
    > > fwiw, I'm an amateur seeking to purchase a camera only for hobby

    purposes,
    > > including some model photography. Trying to decide here between D300,
    > > Dimage A1 or wait for F828.. but I'm in no hurry because searching for

    the
    > > 'best' camera, reading reviews and comments over and over is already

    half
    > of
    > > the fun!
    > >
    > > Thanks
    > >
    > >

    >
    >
     
    Faiser, Oct 25, 2003
    #5
  6. Faiser

    Godfrey Guest

    Tony Spadaro has stated something that could be misleading here.
    The image on the LCD or EVF of any digital camera is ALWAYS through the
    taking lens. Of course, the optical tunnel viewfinders on any camera, film or
    digital, constitute a separate optical system from the taking lens and cannot
    display Depth of Field.

    DoF Preview is a feature for SLR cameras. SLRs use an optical reflex system
    which requires the focusing screen be as bright as possible for accurate
    evaluation of focus. So SLR cameras have mechanisms which hold the lens open
    to maximum aperture except at the moment of exposure, when the mirror is
    flipped up and the viewfinder is dark. DoF Preview allows a photographer to
    override this normal behavior of the camera and preview the scene at the
    taking aperture in order to evaluate depth of field. Digital SLRS work in the
    identical way to film SLRs in this respect.

    Digital cameras that are not DSLRs, with LCD displays and/or EVF displays,
    rely upon other means to keep the viewfinder bright in the normal course of
    operation and normally do not hold the lens at maximum aperture. The result
    is that you are ALWAYS seeing the scene at the actual lens opening that will
    be used when making the exposure. No DoF Preview is required, that's why it
    is missing in the listed features for these cameras.

    As Todd Walker mentioned, digital cameras normally have sensors that are
    quite a bit smaller than 35mm film and, because of that, generally have
    extensive DoF compared to 35mm film cameras. The original reason for DoF
    preview in SLRs was to allow a photographer to check that they had ENOUGH
    depth of field at the taking aperture to cover the focus range required for a
    scene. With most digital cameras, ths is never an issue.

    Godfrey


    On Sat, 25 Oct 2003 5:57:49 -0700, Faiser wrote
    (in message <hrumb.50876$>):

    > So does anybody know if the Minolta DimageA1 actually has Depth of Field
    > preview? It's one of those features that is never mentionned in the
    > reviews/tech specs.
    >
    > "Tony Spadaro" <> wrote in message
    > news:XKgmb.2974$...
    >> There can be no dof preview on any camera where the viewfinder image is
    >> not
    >> from the actual lens. If the EVF is through the taking lens dof preview
    >> should work - but some camreas may not have it.

    [snip]
     
    Godfrey, Oct 25, 2003
    #6
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