Lens with two apertures

Discussion in 'Miscellaneous Equipment' started by baachitraka, Jun 22, 2011.

  1. baachitraka

    baachitraka Subscriber

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    As you might have experienced that squinting human eye can able to see outside world slightly sharper...

    With that, Will adding an another aperture to an existing lens produces any sharper pictures, provided both apertures have same or different opening?

    Just curious...
     
  2. mrred

    mrred Subscriber

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    That's what a ND filter is for.....:smile:
     
  3. baachitraka

    baachitraka Subscriber

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    Last edited by a moderator: Jun 22, 2011
  4. tomalophicon

    tomalophicon Member

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    Would a stereo camera fit the bill? Or is the 2 aperture idea more effective in one lens?
     
  5. baachitraka

    baachitraka Subscriber

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    At-least from Minolta's design(now SONY) looks great.
     
  6. markbarendt

    markbarendt Subscriber

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    The Sony lens is a soft focus lens, not a super sharp lens.

    Mamiya and others have done this for years.

    They don't provide sharper or less sharp images, soft focus lenses treat the out of focus areas differently.

    In the Mamiya 150SF for the RB for example, the glass is designed with spherical aberrations that affect the image when an f stop larger than f/8 is used. (At f/8 and smaller apertures the lens is "normal".) The lens originally came with 3 disks with many small holes around a normal aperture opening.

    These disks allow a user to adjust to f/5, f/5.6, or f/6.3 while leaving the normal aperture control at f/4, the extra holes scattered around the main aperture allow the aberrations to "sneak in" around the edges.

    This is one of my favorite lenses. This lens requires working differently, like stoping down to f/8 to focus and taking the lens apart to set aperture. It's effects are also strongest in the highlights.
     
  7. baachitraka

    baachitraka Subscriber

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    ...but, the samples look okay for me.

    http://www.the135stf.net/samples2.html#galleries/new/Spiky_Planet.jpg

    I am not a fanboy of SONY but just wondering what effect will bring on image quality when two or more apertures are used.


     
  8. markbarendt

    markbarendt Subscriber

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    Like I said the 150SF is a favorite of mine. I like the SF effect.

    The central aperture controls the main/sharp image.

    The filtered area, by holes or whatever around the main aperture, allows the effect, whatever that may be, of the rest of the edges of the glass to be used.
     
  9. baachitraka

    baachitraka Subscriber

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  10. tomalophicon

    tomalophicon Member

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    I have some rough negative scans:
     

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  11. baachitraka

    baachitraka Subscriber

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    Scary weapons ;-)

    Was this shot with the same lens in the discussion.

     
  12. tomalophicon

    tomalophicon Member

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    Yes using the 150mm soft focus for RB67.

    I forget the aperture settings for the others but the girl is F/4 with no disc attached, therefore there is only one aperture :smile:
     
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  13. tomalophicon

    tomalophicon Member

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    And a small work print. Again, I don't remember the aperture.
     

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  15. markbarendt

    markbarendt Subscriber

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  16. tomalophicon

    tomalophicon Member

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    Nice Mark.
     
  17. markbarendt

    markbarendt Subscriber

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    Thank you.
     
  18. markbarendt

    markbarendt Subscriber

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    I like the effect in both shots, like using old Petzvals on LF gear.
     
  19. tomalophicon

    tomalophicon Member

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    Thanks, it's great because I can't afford Petzvals. But I was able to buy the 150 new for $110
     
  20. markbarendt

    markbarendt Subscriber

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    Me too, at least very close to that anyway.
     
  21. markbarendt

    markbarendt Subscriber

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    Had another thought here.

    It isn't that you can see sharper, squinting actually degrades sharpness and clarity.

    What it does do though is simplify the image, because extraneous detail is no longer "distracting" us, the "essence" remains/becomes more clear, not the image itself.
     
  22. baachitraka

    baachitraka Subscriber

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    I do not know whether this is related to this discussion.

    I am wondering why bellows in LF having ridges rather than smooth taper. Curious to know, how light propagates through the ridges.


     
  23. markbarendt

    markbarendt Subscriber

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    There is normally no interference from the ridges, they are normally outside the path the light follows from lens to film.

    Now if the bellows is allowed to sag into the light path then it will simply block the light in that area, nothing reaches the film.

    There is no difference in this effect for a non-ridged, bag, bellows.
     
  24. David Brown

    David Brown Subscriber

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    Probably not.
     
  25. rjbuzzclick

    rjbuzzclick Member

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    The ridges and folds allow the bellows to compress and expand for focusing, and are structural so the bellows will not sag (much) when extended. They also allow a camera to fold up for transport. The bellows are black on the inside to reduce reflections, and larger than the image cone coming out of the lens so no light is propagated through them, and virtually no light is reflected off of them inside the camera.
     
    Last edited by a moderator: Jun 22, 2011
  26. JBrunner

    JBrunner Moderator Staff Member Moderator

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    Probably not. Apertures are usually placed at the nodal point of the lens. There is only one of those. An aperture placed in a different spot either won't have an effect or will become the de facto aperture, but in the wrong place. There are however many "tricks" available in optics, but in the end it's all math and physics, and there is rarely a free lunch with those two.