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Thread: Using a Petzval portrait lens

  1. #11
    Alex Timmermans
    Join Date
    May 2008
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    Holland
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    572

    Re: Using a Petzval portrait lens

    While using a smooth backdrop you will never see swirl. Even when using it wide open.
    You will only see it when the background has a certain pattern or outside when there is a background with leaves or so.
    "You dont take a picture, it's given to you"

    www.alextimmermans.com
    www.collodion-art.blogspot.com
    email : collodion-art dot onsmail dot nl

  2. #12

    Join Date
    Jun 2006
    Location
    Brazil
    Posts
    152

    Re: Using a Petzval portrait lens

    Pere Casals, beautiful picture!!! It is intriguing how come that the lens could focus on the girl and also on the bushes that seem to be half the distance. Otherwise it illustrates the rule of 1/3 of focal length being sharp at image centre.

    My point at the opening of this thread was, in different words, that if you focus on the lens axis you get a circle of sharpness, but if you focus on a peripheral point, in theory, you get not a circle but a ring of sharpness, due to the field curvature. But I don't know whether this is a noticeable effect on the final picture. I will definitely do some tests.

  3. #13

    Join Date
    Jul 2016
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    2,001

    Re: Using a Petzval portrait lens

    Quote Originally Posted by lungovw View Post
    Pere Casals, beautiful picture!!! It is intriguing how come that the lens could focus on the girl and also on the bushes that seem to be half the distance.
    There is a swing, if you observe the plants that are just at left and right of the girl you see that at left plants are out of focus, while at right are sharper. The plane of focus (sphere of focus in this case ) passes by the plants in the left-bottom corner and by the girl.

    Also there is some tilt (I think), as girl is more out of focus near feet.

    Also I feel that placing the swirl in the right place is powerful...

    It looks magics, some "pixel lovers" would have said that a good photoshop work was there !

    I also like it because what is in the back of the girl it is OOF, what she can see in front of his face it is sharp. It suggests me some kind of subject self awareness, just a personal impression.

    https://www.flickr.com/photos/vitali...cPv5Y3-cB6piA/

    LF is great ! I love it !!!

  4. #14

    Join Date
    Jun 2006
    Location
    Brazil
    Posts
    152

    Re: Using a Petzval portrait lens

    I tested it. The attached images show a portrait made with a Derogy Rapide nº4, Petzval type, 223 mm focal length, fully opened, serial number 40022. I used FP4 9x12 cm. First of them I just kept the lens axis centred on film while for the second I shifted lens 2 cm to the left and tilted film and lens board, backwards, in order to get the equivalent to 3 cm lens fall. In both cases I focused the eyes using a loupe. It confirms that there is a noticeable effect of aberrations acting upon the overall impression of sharpness on the off center parts of the image. We can focus on a peripheral part of image and compensate field curvature but this does not correct aberrations that will always be there. When lens axis points to the spot we where we want the best image quality, then we get the best performance the lens can yield. The only way to improve those portions far from center in regards to aberrations is stopping down the lens, as Scott did in his above posted portrait.
    Portrait:
    Click image for larger version. 

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    Eyes with lens axis pointing to film center:
    Click image for larger version. 

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    Eyes with lens axis pointing to subject's eyes:
    Click image for larger version. 

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  5. #15
    multi format
    Join Date
    Feb 2001
    Location
    local
    Posts
    3,797

    Re: Using a Petzval portrait lens

    thankfully the only petzval lenses i have used were
    a focal length longer than my format and i never got the swirls
    they give me a headache and nausea ..

  6. #16

    Join Date
    Dec 2010
    Location
    Santa Barbara
    Posts
    1,295

    Re: Using a Petzval portrait lens

    I think yes.. the bottom or long side of the pix will go progressively crazy out of focus - because of the physics of the curve of the lens

    might be cool though

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