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Thread: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

  1. #11

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    Re: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

    Quote Originally Posted by Emmanuel BIGLER View Post
    Hello Marco !


    - If you use the Imagon at full aperture without the special diaphragm, you get an image which is less interesting, it is simply, expressed in modern language, a poor image delivered by a poorly corrected lens


    - Out of focus images taken with an Imagon have a strange look, due to the fact that strongly defocused part of the image are created by the projection of the shapes in the diaphragm.

    Hello, Emmanuelle,

    that's my first time that I don' t agree with your statements.
    Probably it's a matter of taste, but I love the Imagon wide open and without any disc.

    Imagon 200mm, Xray, 5x7":
    Attachment 170494


    Imagon 200mm, 4x5":

    Attachment 170495


    This nearly gives the characteristically look of a meniskus, with all the lovely fuzz and glow.

    The projection of the shapes from the original diaphragm has more to do with highlights and with "disc open" than with "out of focus".

    Par example, for giving the picture a special flair it is necessary to bring the lens a bit out of focus, but it's mostly a matter of light to have or not to have this projections called "Kühn-bedbugs" in our country.
    Mainly this bedbugs are hooking on highlights, so creating great glow with a lot of light and an opened aperture disc is difficult if not unpossible without this ugly projections.

    Ritchie

  2. #12
    Peter De Smidt's Avatar
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    Re: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

    Hey Ritchie,

    You're attachment links don't work for me.

    Imagon no disk:


    Imagon, Middle disk, holes open:


    Middle disk, holes closed:
    "Why can't we all just get along?" President Dale, Mars Attacks

  3. #13

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    Re: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

    Thanks, Peter, I hope this will work now:

    Click image for larger version. 

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ID:	170498

    Click image for larger version. 

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ID:	170499

  4. #14
    Marco Gilardetti's Avatar
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    Re: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

    Thanks to anyone who participated in this thread with comments, images and documents (yes, I do read french!).

    In my unity, the shutter and the diaphragm are both in front of the lenses as someone already pointed out. It's good to know that also the standard diaphragm can be used with no issues.

    Although the Rodestock's user's manual also refers to a 4X neutral density filter, my unit came with a less useful yellow/green 2X filter. The set was possibly made before the user's manual was printed.

    It is absolutely beyond my comprehension how can it be that the lens has a h=5.8 aperture, and then when the larger diaphragm is installed and part of the light is blocked, the aperture still stays at h=5.8. Can anyone comment on this, perhaps?

  5. #15

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    Re: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

    Quote Originally Posted by Marco Gilardetti View Post
    Thanks to anyone who participated in this thread with comments, images and documents (yes, I do read french!).

    In my unity, the shutter and the diaphragm are both in front of the lenses as someone already pointed out. It's good to know that also the standard diaphragm can be used with no issues.

    Although the Rodestock's user's manual also refers to a 4X neutral density filter, my unit came with a less useful yellow/green 2X filter. The set was possibly made before the user's manual was printed.

    It is absolutely beyond my comprehension how can it be that the lens has a h=5.8 aperture, and then when the larger diaphragm is installed and part of the light is blocked, the aperture still stays at h=5.8. Can anyone comment on this, perhaps?
    It remains at 5.8 when the largest disk is used with all of the periphery holes open. It is 7.7 when those holes are closed.

    As the Imagon actually is two different focal lengths, one in the center of the lens and one at the edge of the lens you would defeat the purpose of the Imagon by using the shutter’s aperture ring as that would block the peripheral rays.

  6. #16
    Marco Gilardetti's Avatar
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    Re: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

    Quote Originally Posted by Bob Salomon View Post
    It remains at 5.8 when the largest disk is used with all of the periphery holes open.
    OK. And how is this possible, from a physics standpoint, since part of the light reaching the front lens is being blocked?

  7. #17
    Peter De Smidt's Avatar
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    Re: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

    Got them this time, Plaubel. Thanks!
    "Why can't we all just get along?" President Dale, Mars Attacks

  8. #18
    Peter De Smidt's Avatar
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    Re: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

    This is using a Waterhouse-style stop in front of the lens, i.e. not using the official disks:

    47mm opening:


    57mm opening:
    "Why can't we all just get along?" President Dale, Mars Attacks

  9. #19
    Jac@stafford.net's Avatar
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    Re: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

    Quote Originally Posted by Marco Gilardetti View Post
    OK. And how is this possible, from a physics standpoint, since part of the light reaching the front lens is being blocked?
    The ƒ stop (h stop) is given for the holes open with that sieve, not for the naked lens.

  10. #20

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    Re: Rodenstock Imagon Tiefenbildner 250mm h=5.8, some questions.

    Hello all ! A nice discussion about the Imagon !!

    Thanks to Mark Sawyer for correcting me regarding the placement of different elements in the Imagon.
    The reason is: I have a shutter-less Imagon, and I remembered a diagram on a Rodenstock brochure (e.g. like the one on cameraeccentric's web site, I have another one in French) where the lens is presented with light entering from the right, unlike most conventional optical diagrams where light comes from the left. My mistake.

    And thanks to Plaubel-Richtie for his comments which set the point on the question: do you like or not the special Imagon look? With or without perforated disk? I agree that the question is a matter of taste.

    And thanks to Peter de Smidt for sharing the convincing pictures which demonstrate how the Imagon behaves.
    In the series, I prefer sharper images, hence I prefer the ones with the perforated disk in place i.e. with the central part delivering an image somewhat corrected from spherical aberration and superimposed to a delicate "halo" of fuzziness.

    However the when the shapes of this perforated disk are projected in out-of focus highlights, the visible shape is definitely non-natural and somewhat disturbing, I agree.

    So with the Imagon, you should only take pictures of flat subjects with no depth, focused with the outer holes closed and then re-opened, if you want to see the added fuzziness but do not want to see the disturbing shapes in the background

    Not kidding, the out-of focus shape of a bright spot in Peter's image has a complex shape, as if there was another parasitic reflection added to what you would expect from the projection of the iris, looks like two projections of the iris with different magnifications?
    Attached Thumbnails Attached Thumbnails Faux_Imagon_Middle_Disk_open_cropped_background.jpg  

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