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Thread: Darlot-made Petzval with iris diaphragm

  1. #1
    cyberjunkie's Avatar
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    Darlot-made Petzval with iris diaphragm

    I love french vintage lenses, so i took the chance and purchased two unmarked brassies which definitely look Darlot made.
    One is clearly a Petzval made for photographic use, with factory-made cut for waterhouse stops.
    It has two features that sets it apart from the other 3 Darlots i own:
    1) there is no lens shade, and no thread to fit one (like with projection petzvals)
    2) the characteristic Darlot knob has a double, rounded knurl on its periphery, different from the simple flat, knurled surface that's commonly found (Google Pictures shows a lot of examples of the latter build, and only a few of the former). It is strange that both my new lenses share the same knob design, while the others i own have the simpler one.

    All in all, nothing unconventional. The true reason for posting this thread is the second lens.
    It looks like a Darlot-made Petzval, with badly ruined lacquer, and in not-so-good condition.
    There is an iris diaphragm though, scaled from 1 to 5.
    The second and third pictures show the iris, seen from both sides of the barrel.
    The position of the diaphragm is where you should expect it to be, with a Petzval design (i.e. 2/3 of the length, from the front of the lens).
    That should place the word END to my speculations about the nature of the lens, BUT i remember having seen one of the many anachromatic designs manufactured by Darlot, which had roughly the same aesthetical features.

    Any clue?
    Of course i will (try to) disassemble the lens and clean the glasses, once i have it in my hands, and that will provide the answer... but it will take some time, and i am too curious and impatient to keep my doubts for myself.
    If some interesting informations will be provided, it could even prove to be a worthy reference for future searches, who knows...
    Attached Thumbnails Attached Thumbnails Darlot petzval 1.JPG   NEW-ITEMS_70022-2.jpg  
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    CJ

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    cyberjunkie's Avatar
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    Re: Darlot-made Petzval with iris diaphragm

    Last edited by cyberjunkie; 15-Oct-2012 at 10:36. Reason: forgot the pictures!
    have fun
    CJ

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    Re: Darlot-made Petzval with iris diaphragm

    All the Petzvals I have seen with 1 - 5 equi-distant aperture scales were from horizontal enlargers.

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    cyberjunkie's Avatar
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    Re: Darlot-made Petzval with iris diaphragm

    Thanks Steven.
    Once more, an interesting information!

    I am sure you're right, but one thing comes to my mind:
    it is strange that a lens especially made for darkroom use was made with a shade.
    An enlarging Petzval should be closer to a projection one, than to a model for taking pictures.
    From my own lenses, i learned that projection Petzvals were usually made without shade... though i have a couple exceptions WITH shade.
    Of course it's always difficult to be certain about the intended use of early Petzvals with no waterhouse slot...
    have fun
    CJ

    WTB (and pay good monet for):
    soft back cell for Ilex Photoplastic 5x7
    disks for Imagon 420mm
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    5x7 conversion for Bi-System

    for sale
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    Re: Darlot-made Petzval with iris diaphragm

    I sold one, some time back, with red enamel in the engraved numbers. Yours, I think, has white enamel. Both can be seen in a safe light environment.

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    cyberjunkie's Avatar
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    Re: Darlot-made Petzval with iris diaphragm

    Got both lenses.
    The Petzval with iris diaphragm needs a light cleaning, the most notable feature is that the iris blades are RED. With ortho films it makes little or no difference, even less so if used in the darkroom.
    The other one, which looked almost perfect in picture, requires more tinkering.
    The optic came in a wooden lensboard, with original flange, but it is reversed!
    The front achromat, with lens shade, is pointing towards the film, and at the front there are the two flint and crown glasses which are supposed to be at the back side.
    Front and back threads are identical, but it's impossible to reverse the way the elements are mounted: the ring which should support the inner lens of the back couple is located at the front!
    I tried to remove the ring, with a wooden shaft and a lot of hammering, but to no avail.
    My best guess is that the lens was disassembled for cleaning (the glass elements are spotless), and that the ring was pushed down at the wrong end of the barrel... but i am not sure about it.
    I am not even sure if the ring is fixed by interference, or glued/riveted. By visual inspection i don't see anything that is holding the ring in place, but the inner side is not easy to access, as there is the restriction for the waterhouse slot.
    The same restriction does not allow to push the ring flat. I did a lot of hammering sideways, removed some of the blackening, but the ring didn't move a single micron.
    Before going very hard, or trying to make a wooden instrument that would allow to push down flat, i think i am going to wait for any helpful input.

    Did you encounter a similar problem with Darlot-made petzvals?
    Any helpful hint by those who frequently restore this kind of lenses?
    Attached Thumbnails Attached Thumbnails Darlot-made upsidedown 1.JPG   Darlot-made upsidedown 2.JPG  
    have fun
    CJ

    WTB (and pay good monet for):
    soft back cell for Ilex Photoplastic 5x7
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    5x7 conversion for Bi-System

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    Re: Darlot-made Petzval with iris diaphragm

    No time tonight to think about the stuck ring but...

    Perhaps this is the correct optical Petzval mount for an enlarger. The image comes from inside, through the achromat and then the "rear" pair and then is thrown up on the wall/photo paper? This means, of course, that the correct way to mount a Petzval in a magic lantern is also the reverse!

    This could explain why so many projection have "incorrect" rear and front cells when purchased on e**y.

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    cyberjunkie's Avatar
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    Re: Darlot-made Petzval with iris diaphragm

    It is not the first Petzval with red diaphragm leaves.
    It's the other one (have a look at the two pics i attached to my previous post).
    It is a conventional photographic Petzval, almost identical to other Darlot-made objectives with waterhouse slot. Why on earth a lens shade should be pointing towards the inner of the camera/lantern/enlarger?
    BTW, any non-symmetrical lens, with the stop located at 1/3 of the length (default configuration with any Petzval with provision for a stop), can't be reversed without also turning the orientation of the barrel. Other way some aberrations would go out of control.

    The pics show how i got the lens: achromat and lens shade behind the lensboard, air spaced pair at the front.
    The achromat cell can be fitted at the front, but the other two glasses can't be fitted at the back, because there is no "base" ring where the inner element can be seated.
    I hope i made it clear.
    If i didn't, i can take a picture of the innards of the barrel

    thanks
    have fun
    CJ

    WTB (and pay good monet for):
    soft back cell for Ilex Photoplastic 5x7
    disks for Imagon 420mm
    5x7 back for Calumet C1
    5x7 conversion for Bi-System

    for sale
    Photographica

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