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john10

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Posts posted by john10

    Resolution Target - Air Force PDF File?

    in Large Format

    Posted

    <html>

     

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    <meta http-equiv="Content-Type" content="text/html; charset=windows-

    1252">

    <meta name="GENERATOR" content="Microsoft FrontPage 4.0">

    <meta name="ProgId" content="FrontPage.Editor.Document">

    <title>New Page 2</title>

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    <p class="MsoNormal">Sorry folks. My brain is not yet back into gear

    after the

    Christmas break.</p>

    <p class="MsoNormal">The link for a military lens-testing chart is at

    the

    following link.</p>

    <p class="MsoNormal"><a

    href="http://www.jmlopt.com/products/targpatt/summary_ch9.html">http:/

    /www.jmlopt.com/products/targpatt/summary_ch9.html</a></p>

    <p class="MsoNormal">Best wishes,</p>

    <p class="MsoNormal">John</p>

     

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    Info on Schnieder Dasykar lenses needed.

    in Large Format

    Posted

    My information is that the Dasykar lenses were some of the earliest

    Schneider lenses, so were from the 1920's. They were intended for

    architectural, interior, and panoramic photography, and also

    photogrammetry. They were replced by the Angulons in about 1930.

     

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    They were for 90 to 110 degrees angle of view and were made from 60mm

    to 440mm focal lengths.

     

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    The 130mm will cover 7" x 9.5" stopped down. The 180mm will cover 7"

    x 9.5" fully open.

    My Ilex Acuton

    in Large Format

    Posted

    Perhaps you could check if the front and rear elements are inscribed

    with their individual focal lengths. It is possible that the single

    elements are of 300mm focal length each and the combination of the

    two elements is 180mm. This could quite easily be checked out with a

    test on the camera.

     

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    Simply focus the complete lens on an infinity subject and measure the

    distance from the lens flange to the ground glass and similarly with

    the front element removed. If my guess is correct the measured

    distances will correspond at 180mm and 300mm respectively. The Ross

    combinable lenses worked on this principle, so it is quite possible

    that this one does also.

    Pinhole

    in Large Format

    Posted

    You could try the following links for starters but also try a Google

    search (www.google.com). Type 'pinhole camera' into the search box

    and you will get many sources of information.

     

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    http://www.photo.net/photo/pinhole/pinhole.htm

     

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    http://members.home.net/hmpi/Pinhole/Articles/PinholeArticles.htm

     

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    http://amateurphoto.about.com/hobbies/amateurphoto/msub17.htm

     

    <p>

     

    http://pinholeresource.com/

     

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    http://www.pinhole.org/

     

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    http://dir.yahoo.com/Arts/Visual_Arts/Photography/Pinhole_Photography/

     

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    John at JCR Cameras

    big....BIG aerial lense question

    in Large Format

    Posted

    To find the approximate maximum aperture of a lens measure the focal

    length of the lens by projecting a sharp infinity image of the

    horizon as seen through your room window onto an internal wall and

    measure the distance from the centre of the lens to the wall. Then

    measure the diameter of the lens in the same units. Divide the focal

    length by the diameter to give the maximum aperture. In this case it

    would appear to by 45/6 = f7.5.

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