Bokeh and Aperture Shape

Discussion in 'Digital Photography' started by Ali, Jul 8, 2007.

  1. Ali

    Ali Guest

    Just watched Die Hard 4 and I noticed that the Bokeh in the close-up shots
    looked a bit unattractive, particularly with light sources in the
    background. Look like 8 blade apertures, but not smooth edges. Very
    distinctive shape.

    Just curious, is there a reason for the difference between high-end video
    lenses and high-end still lenses with regards to aperture?
     
    Ali, Jul 8, 2007
    #1
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  2. Ali

    RockyZ Guest

    On Sun, 8 Jul 2007 21:37:38 +0100, "Ali" <> wrote:

    >Just watched Die Hard 4 and I noticed that the Bokeh in the close-up shots
    >looked a bit unattractive, particularly with light sources in the
    >background. Look like 8 blade apertures, but not smooth edges. Very
    >distinctive shape.
    >
    >Just curious, is there a reason for the difference between high-end video
    >lenses and high-end still lenses with regards to aperture?
    >


    Bokeh effects not only depend on the shape of aperture in use, but exactly where
    in the lens' light-path that aperture is physically situated. This is why
    different lens designs produce different bokeh. It is not video nor still-frame
    equipment dependent, just lens-design dependent. Some lens designs might have
    the aperture blades between elements 4 and 5 of a 9 element, 5-groups lens.
    Another lens design might have the f/stop aperture between lens elements 2 and 3
    of a similar 9 lens design. It all depends on how the lens designer wants to
    arrange things by balancing cost, efficiency, and image quality as well as the
    type of glasses selected for that particular lens design. (A lens' resulting
    bokeh is not usually a high-priority with lens designers. Chromatic aberrations,
    field flatness, and angular distortions are of much greater importance.) If you
    want to experiment with different aperture shapes and how those aperture edges
    can impact the bokeh in an image, get a plugin called "Lenscare" from
    http://www.frischluft.com/ , it works in all editors, even freeware IrfanView.
    You won't be able to see how the aperture position within a lens design will
    change the bokeh. It would require an advanced optics CAD program with
    ray-tracing capabilities for that, (there are some excellent ones out there,
    they're fun to use). However, you will be able to see how sharp and soft edges,
    different shapes, and how much of the diffraction energy is dispersed in
    different regions of the lens' aperture can change the bokeh.
     
    RockyZ, Jul 9, 2007
    #2
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  3. On Jul 8, 3:37 pm, "Ali" <> wrote:
    > Just watched Die Hard 4 and I noticed that the Bokeh in the close-up shots
    > looked a bit unattractive, particularly with light sources in the
    > background. Look like 8 blade apertures, but not smooth edges. Very
    > distinctive shape.
    >
    > Just curious, is there a reason for the difference between high-end video
    > lenses and high-end still lenses with regards to aperture?


    I had a friend and associate, a super lens designer, who did quite a
    study on this. He wrote a paper that was, as far as I know,
    unpublished. He did, however, do a shortened and simplified version
    for the "gleanings" column of Sky and Telescope. This would be back
    in late 70s or early 80s. He did quite a few cases with very odd
    shaped apertures and some with multiple, close spaced apertures. His
    name is David Stolzman. I believe I have a copy of his longer paper
    somewhere in my files, but it will take me awhile to find it.

    This study was so interesting I have been long tempted to make a
    pinhole camera with replaceable apertures and make a series of photo-
    etched apertures. One idea he played with was a graded edge aperture
    that could also be photo reproduced. This is sometimes called an
    apodized aperture.
     
    Don Stauffer in Minnesota, Jul 9, 2007
    #3
  4. Ali

    Ali Guest

    Thank you for your post, however surely camera equipment on a blockbuster
    movie for these types of shots should have nice bokeh?


    "RockyZ" <> wrote in message
    news:...
    > On Sun, 8 Jul 2007 21:37:38 +0100, "Ali" <> wrote:
    >
    > It all depends on how the lens designer wants to
    > arrange things by balancing cost, efficiency, and image quality as well as
    > the
    > type of glasses selected for that particular lens design. (A lens'
    > resulting
    > bokeh is not usually a high-priority with lens designers. Chromatic
    > aberrations,
    > field flatness, and angular distortions are of much greater importance.)
     
    Ali, Jul 9, 2007
    #4
  5. Ali

    Zen Diver Guest

    Ali wrote:
    > Just watched Die Hard 4 and I noticed that the Bokeh in the close-up
    > shots looked a bit unattractive, particularly with light sources in the
    > background. Look like 8 blade apertures, but not smooth edges. Very
    > distinctive shape.
    >
    > Just curious, is there a reason for the difference between high-end
    > video lenses and high-end still lenses with regards to aperture?
    >
    >


    It is entirely possible that the lens was chosen specifically for this
    feature. The Director of Photography for this sort of production would
    have all manner of lenses at their disposal. These guys are masters of
    their craft and are able to select tools to produce the result they want.
     
    Zen Diver, Jul 10, 2007
    #5
  6. Ali

    Ali Guest

    Absolutely, I agree. That's why I am curious why they used a lens with this
    bokeh. There must be a reason for it.


    "Zen Diver" <> wrote in message
    news:...
    >
    > It is entirely possible that the lens was chosen specifically for this
    > feature. The Director of Photography for this sort of production would
    > have all manner of lenses at their disposal. These guys are masters of
    > their craft and are able to select tools to produce the result they want.
     
    Ali, Jul 10, 2007
    #6
  7. On Tue, 10 Jul 2007 18:48:52 +0100, "Ali" <> wrote:

    >Absolutely, I agree. That's why I am curious why they used a lens with this
    >bokeh. There must be a reason for it.


    The choice of a lens has to do with the look of that lens. A lens can be
    tacksharp, or nice and soft. Has flares which the DP can like, low or high
    contrast, etc etc.

    cheers

    -martin-
    --
    Official website "Jonah's Quid" http://www.jonahsquids.co.uk
     
    Martin Heffels, Jul 10, 2007
    #7
  8. On Jul 10, 3:14 pm, Martin Heffels <> wrote:
    > On Tue, 10 Jul 2007 18:48:52 +0100, "Ali" <> wrote:
    > >Absolutely, I agree. That's why I am curious why they used a lens with this
    > >bokeh. There must be a reason for it.

    >
    > The choice of a lens has to do with the look of that lens. A lens can be
    > tacksharp, or nice and soft. Has flares which the DP can like, low or high
    > contrast, etc etc.
    >
    > cheers
    >
    > -martin-
    > --
    > Official website "Jonah's Quid"http://www.jonahsquids.co.uk


    Different spot profiles create different looks. For instance, a
    diffraction blur has a completely different look than an out of focus
    blur, which is different than the blur from many aberrations. In
    fact, almost all lens aberrations give a unique look. Not all blur is
    the same.
     
    Don Stauffer in Minnesota, Jul 11, 2007
    #8
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