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Thread: Focusing A Petzval

  1. #1
    Unwitting Thread Killer Ari's Avatar
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    Focusing A Petzval

    Not obvious to me, I can't seem to get my lens to focus where I want it - sometimes. Mostly with full-length portraits (head to feet).

    As I've written in another thread, I find that much depends on subject-to-camera distance.
    When I shoot a full-length photo, the face is in the "blur zone" of the lens, even if it's precisely focused.
    The solution is to reframe it so that the head is in the center of the frame, and uses the lens' "sweet spot".

    When I try to use front rise/fall to place the sweet spot in the top third of the frame, it seems to take the blur zone with it.
    However, if I move in closer to the subject, the face takes up a large portion of the sweet spot, and framing is easier and more pleasing.

    Posted this elsewhere, but thought it would help here, too: https://apenasimagens.com/en/using-p...lens-potraits/

  2. #2
    Foamer
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    Re: Focusing A Petzval

    You have to put the sharp center on the spit you want sharp. Forget about movements.


    Kent in SD
    Qui sedes ad dexteram Patris,
    miserere nobis.

  3. #3
    Tin Can's Avatar
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    Re: Focusing A Petzval

    That's why I have 'Plastika' made in China $60 full size mannequin with clothes and wig

    I can set up lighting, test focus etc

    one day I want a sitting one

    Tomorrow look for her eye
    2022

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    Re: Focusing A Petzval

    Some Petzvals I have used were very sharp right in the center but focus fall-off can be severe with some (esp modernish projection Petzvals)... And composition rarely likes center of intrests in the center of frame...

    One trick I do in still lifes is to unsharpen center areas by a little front tilt or swing that puts lens a little off axis where overall definition goes down, so evens out effect sometimes...

    This is one of those times a true soft focus lens pays off, as the effect tends to be more uniform across frame...

    Steve K

  5. #5
    Mark Sawyer's Avatar
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    Re: Focusing A Petzval

    It's called "learning". Don't you just hate it?
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

  6. #6
    Unwitting Thread Killer Ari's Avatar
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    Re: Focusing A Petzval

    Quote Originally Posted by Mark Sawyer View Post
    It's called "learning". Don't you just hate it?
    Yeah, sucks.
    I'm having a lot of fun getting acquainted with this lens. It's not what I'm used to but the benefits of getting it right are immensely rewarding.
    The images it can make when properly used amaze me.

  7. #7
    Drew Bedo's Avatar
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    Re: Focusing A Petzval

    The Petzval design was a breakthrough because it allowed a relatively wide maximum aperture in a day when the most advanced sensitized Daguerreotype technique made plates with an "ISO" equivalent to something less than 1. The Petzval design allowed for exposures under a minute and for the first time, indoor photography was possible.

    This all came with a limitation: Curvature of field. These lenses are only sharp in the middle. That is why many old photogrpahs are in oval frames. That is probably (and I am guessing) that the iconic early Voightlander camera is cone shaped and takes circular plates. Much of the effort in the next fifty years of lens design was directed at eliminating curvature of field while keeping maximum aperture usably wide. Some Rapid Rectilinear desighs open up no larger than f/16.

    Here is a good article that gives an overview of this.
    https://en.wikipedia.org/wiki/Petzval_lens

    Understand, its not you or your technique . . .its the lens. Learn to love it for what it is.
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  8. #8
    Unwitting Thread Killer Ari's Avatar
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    Re: Focusing A Petzval

    Thanks Drew.
    I already love the lens, I just need to master it now.

  9. #9
    Drew Bedo's Avatar
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    Re: Focusing A Petzval

    Full disclosure Ari: I have never owned or used a Petzval lens.

    Now, in another thread I wondered how the curvature of field could be used in creating an image. My thought was that a subject such as a room or hallway might be rendered sharp at the edges under some circumstances. it might be interesting to focus on something and move targets on the edge to define the curved zone of focus.

    Dunno if any of that is of any value.
    Drew Bedo
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    There are only three types of mounting flanges; too big, too small and wrong thread!

  10. #10
    Mark Sawyer's Avatar
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    Re: Focusing A Petzval

    Historical trivia: at the same time Petzval was designing the Petzval Portrait Lens, he also designed the Petzval View Lens. It had a fairly flat field, covered a wider angle, and was fairly sharp to the corners. But it was slower at f/9 to f/14, so it wasn't suitable for portraits and didn't go into production for another ten years, when it was renamed the Orthoskop/Orthoscop/Orthoscope, depending on who made it. (Dietzler made it in partnership with Petzval, Voigtlander made it without Petzvals permission, and Ross, CC Harrison, and probably a few others also produced them.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

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