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

  1. #21

    Join Date
    Jan 2002
    Besançon, France

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

    And another idea regarding the h-number.

    To me it could be defined like this:
    #1 Take a picture of a gray card, properly focused, with the Imagon fitted with the special iris. Focus with the outer array of perforations closed, then re-open. Measure the illumination in the image plane.
    #2 Substitute to the special iris a simple circular hole centered on the optical axis, located in front of the glass at the same place, do not re-focus in order to keep exactly the same distance between the glass and the image.

    When both experiments yield the same illumination, the h-number in #1 experiment is equal to the regular f-number in #2.

  2. #22
    Peter De Smidt's Avatar
    Join Date
    Jan 2001
    Fond du Lac, WI, USA

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

    I dislike the funky aperture artifacts that appear on specular highlights in the background. I would avoid such highlights if I used the lens disk with the holes open. Note that using a regular iris in front of the lens would get rid of that behavior, and if you made the diameter of the disks smaller, you'd get sharper results, but with less of a glow. I prefer some sharpness + a glow, but that's subjective, of course.
    "Why can't we all just get along?" President Dale, Mars Attacks

  3. #23

    Join Date
    Mar 2011

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

    Quote Originally Posted by Emmanuel BIGLER View Post

    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
    Sorry, Emmanuel, but again I don't agree with the out-of focus-theme.
    The main thing for creating disturbing shapes is direct light - of course in the out-of-focus-areas.
    But it's not the out-of-focus area herself.
    Again I read the manual of the Imagon, written by Michael Neumüller in his great book "the praxis of softfocus" from around 1950.
    He describes " a special case is direct light, which requires closing the disk to avoid spreading highlights" (bedbucks).

    He also describes the effect of increasing and decreasing the sharpness AND the glow by playing with the bellows distance but doesn't give a warning concerning spreading shapes in this situation.

    I have learned to work with my Imagon exclusively from this book, so unfortunately I haven't more to say by own observations than this :-)

    Concerning the iris of a shutter, let me throw in that Neumüller describes why it is best to put the iris in front of a meniscus (the Imagon is a kind of meniscus).

    If the iris is behind the lens, this may give an effect which I can't translate exactly by word, but this may give problems at the edge between shadow and light.

    I didn't use a meniscus with a shutter iris, but the resulting effect is described as a similary effect like burning a print in a bad way.

    This effect seems to be more little, so I have problems to follow his examples given by pictures, but I want to spread the old news :-)

    I didn't found the formula for the distance lens/front iris at this moment, but I remember nearly 10 percent of the focal length was given as the best distance.
    I try to refind this formula.


  4. #24
    Drew Saunders drew.saunders's Avatar
    Join Date
    Dec 2006
    Palo Alto, CA

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

    Cameraeccentric has two scans of old Imagon documents: and

    Your shutter most likely needs to be serviced, or at least test it to see what speeds you actually get at each setting. Yes, you use the same H-stops value as F-stop when determining exposure, but if your shutter is a stop or more off, you're going to have problems. If you're not familiar with compound shutters, you can easily break one if you try to cock the shutter in "B" or "T" mode ("T" might be labeled "Z" on your shutter). Here's a video of the Imagon 300 in box, and Eddie shows you how NOT to break your shutter:

    I have a recent (post 1980 I guess) 250 Imagon in Copal shutter with all the disks and the 4-stop ND filter (more useful these days than the 2-stop green filter) and mostly use the 7.7/9.5 disk, at either setting. You'll get different results using the 5.8/7.7 disk at 7.7 than you will using the 7.7/9.5 at 7.7, so you'll want to experiment to see which one you like. As others have said, you're welcome to use the aperture either with or without the disks. I sometimes stop the aperture down w/o any disks to help focus, choose a disk, re-confirm focus, choose a disk setting, and then shoot.
    Flickriver (to avoid Flickr's annoying new format):

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