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Thread: Petzval vs. Projection Petzval

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    Unwitting Thread Killer Ari's Avatar
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    Petzval vs. Projection Petzval

    Hi all,
    I'm familiar with the kind of image a Petzval lens will make; how would the projection Petzval's images be different?
    Given the same maximum aperture and same focal length, are there any significant differences in the images there two lenses make?
    I know that the projection Petzval had a slightly different design, so are there also any ways to tell them apart by looking at the lenses?
    Here's a B&L Petzval, a type I see often; projection or regular Petzval? Thanks


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    Re: Petzval vs. Projection Petzval

    This is not made to be a generalization in any way but only my experience. Over the years have owned and used a number of Petzval lenses. At one time owned a brass 1800s Petzval and a newer projection Petzval lens, both being of the same focal length. When taken apart to clean the optics, the lens spacing was definitely different. The Brass 1800s Petzval had its typical Bokeh. The projection Petzval optic had, in comparison, little Petzval Bokeh. I'm sure another member with more knowledge of optics will pipe in with a more detailed post.

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    Drew Bedo's Avatar
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    Re: Petzval vs. Projection Petzval

    I am not a lens guru. Many here know sdpecifics out to several decimal places . . .w3hich I respect and admire.

    Here is my understanding: The projection lenses will not have a provision for drop-in stops but will usually have a focusing rack. There may be a pivoting lens cover. . The lenses made for cameras may have a slot for drop-in stops. Camera lenses may or may not have a focusing rack. Optically, I think they are the same.
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    Unwitting Thread Killer Ari's Avatar
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    Re: Petzval vs. Projection Petzval

    Thanks, Drew, but I'm looking for differences in image characteristics.
    Greg, sounds significant; if anyone has images to share, please post.

    From Camera-Wiki: A simplified design had significant use as projection lenses for film. It had second doublet cemented and its positive component placed anterior.
    Seems to indicate that the lens shown above is a projection lens.
    So we know what makes its construction different; I'd like to see this in practice, if possible.

    Thanks

  5. #5
    Foamer
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    Re: Petzval vs. Projection Petzval

    My experience, based on about a dozen photo Petzvals and two projection Petzvals, is the projection ones have less coverage.


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    Unwitting Thread Killer Ari's Avatar
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    Re: Petzval vs. Projection Petzval

    Thanks, Kent; any difference in how they render images?

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    Mark Sawyer's Avatar
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    Re: Petzval vs. Projection Petzval

    Unless you've pulled it apart, I wouldn't be certain that's a Petzval. B&L made a lot of triplets that looked like that.
    "I love my Verito lens, but I always have to sharpen everything in Photoshop..."

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    Unwitting Thread Killer Ari's Avatar
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    Re: Petzval vs. Projection Petzval

    Forgot about those B&L triplets; thanks, Mark.

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    Re: Petzval vs. Projection Petzval

    To me (I've had hundreds of Petzvals) the ones made for photography would have been made more carefully. For example, the lens grinder and polisher would have been checking the results and quality as they make a photographic lens, with the tools of the day. The projector/magic lantern lenses would not have had as much care. They would probably make those lenses for them in lots, then just assembled them from trays full of glass elements. Probably didn't even test them. A projector lens in say 1890 would cost about $5, a photograph lens from the same company about $25 to several hundred. You get what you pay for.

    What would you see with a "poor quality" is more aberrations; coma, swirl, spherical, etc. Those are NOT the "petzval signature", a good lens company tried to get rid of those aberrations. But they wouldn't have messed with projector lenses.

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    Unwitting Thread Killer Ari's Avatar
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    Re: Petzval vs. Projection Petzval

    Garrett, that's exactly the information I was looking for.
    Many thanks for a clear, detailed explanation!

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