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Thread: Why can't all lens diaphrams be like this one?

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    Senior Member RichA's Avatar
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    Why can't all lens diaphrams be like this one?


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    Re: Why can't all lens diaphrams be like this one?

    - because they would be slow
    - because they would be expensive

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    Re: Why can't all lens diaphrams be like this one?

    They need not be slow. Clear aperture of Rich's Wollensak (I have a 240/4.5) is likely to be ~60-70mm.

    Of course they will be expensive! Even 5 bladed ones are!

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    Re: Why can't all lens diaphrams be like this one?

    Quote Originally Posted by Vivek View Post
    They need not be slow. Clear aperture of Rich's Wollensak (I have a 240/4.5) is likely to be ~60-70mm.
    That's not what I mean. I mean that for an SLR, or any other auto-diaphragm camera, a many-bladed iris like this has a lot of static friction and is going to operate slowly as a result.

    You'll never see a Nikon D3s running 8 fps with a lens that has an iris like this...

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    Re: Why can't all lens diaphrams be like this one?

    Quote Originally Posted by Godfrey View Post
    That's not what I mean. I mean that for an SLR, or any other auto-diaphragm camera, a many-bladed iris like this has a lot of static friction and is going to operate slowly as a result.

    You'll never see a Nikon D3s running 8 fps with a lens that has an iris like this...
    Good point!

    But, we do not have that problem with the m4/3rds and the CDAF, do we?

    BTW, Rich, I checked a few Kodak Anastigmats I have (and the Raptars) all have round apertures. The Schneider Clarons have them, APO Nikkors (process lenses) have them...

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    Re: Why can't all lens diaphrams be like this one?

    Quote Originally Posted by Vivek View Post
    Good point!
    But, we do not have that problem with the m4/3rds and the CDAF, do we?
    ..
    Well, all lenses built to date for Micro-FourThirds are designed for open-aperture metering and focusing with auto-iris operation. The cameras don't need it to operate well, but it does help.

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    Senior Member RichA's Avatar
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    Re: Why can't all lens diaphrams be like this one?

    Quote Originally Posted by Vivek View Post
    Good point!

    But, we do not have that problem with the m4/3rds and the CDAF, do we?

    BTW, Rich, I checked a few Kodak Anastigmats I have (and the Raptars) all have round apertures. The Schneider Clarons have them, APO Nikkors (process lenses) have them...
    I've even seen some c-mount lenses with inward facing scallops on the aperture blades! Interesting what you come across.

  8. #8
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    Re: Why can't all lens diaphrams be like this one?

    Quote Originally Posted by Godfrey View Post
    You'll never see a Nikon D3s running 8 fps with a lens that has an iris like this...

    Aaaaahm, a D3s not, but my F2H will do 10per second with that lens:sleep006::
    reason is: On the F2High speed the Nikkor lenses are always in stop down mode. If You press the "stop dowm" knob diaphragms open.
    Camera was not able to close & open diaphragms 10 times a second....

    be fast
    Thomas

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