Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 68,672   Posts: 1,481,816   Online: 1135
      
Results 1 to 7 of 7
  1. #1

    Join Date
    Sep 2009
    Location
    South Bend
    Shooter
    8x10 Format
    Posts
    48

    How to focus to infinity?

    I guess I never thought of this before but, how does one focus a view camera to infinity??

    Although I'm sure the answer will be painfully obvious and I'll be embarrassed I asked, I have to ask.

    Do you need to know the focal length of your lens?

  2. #2
    jbbooks's Avatar
    Join Date
    Apr 2005
    Shooter
    Multi Format
    Posts
    173
    Actually, this is a quick and dirty way to find the focal length of a lens. Just pick a distant object that is small and easy to determine that it is in focus; like hardwood tree branches in winter or lights, wires, fences, etc. and focus it on the ground glass. When in focus, the camera is focused at infinity for that lens. The distance from the face of the lens board to the plane of the ground glass will be the approximate focal length of the lens.

  3. #3

    Join Date
    Mar 2008
    Location
    San Diego, CA, USA
    Shooter
    Multi Format
    Posts
    2,071
    Images
    21
    Quote Originally Posted by jbbooks View Post
    Actually, this is a quick and dirty way to find the focal length of a lens. Just pick a distant object that is small and easy to determine that it is in focus; like hardwood tree branches in winter or lights, wires, fences, etc. and focus it on the ground glass. When in focus, the camera is focused at infinity for that lens. The distance from the face of the lens board to the plane of the ground glass will be the approximate focal length of the lens.
    It'll be the exact focal length of the lens, won't it? Modulo the fact that "infinity" isn't really infinity, which should make a microscopic difference if you picked a nice distant object, and any slop in choosing your points of measurement. Am I missing something that makes it only an approximation?

    -NT
    Nathan Tenny
    San Diego, CA, USA

    The lady of the house has to be a pretty swell sort of person to put up with the annoyance of a photographer.
    -The Little Technical Library, _Developing, Printing, And Enlarging_

  4. #4
    lxdude's Avatar
    Join Date
    Apr 2009
    Location
    Redlands, So. Calif.
    Shooter
    Multi Format
    Posts
    6,454
    Nathan-
    The rear nodal point of the lens, the distance from which to the film plane is the focal length, is not necessarily on the same plane as the face of the lens board.
    Last edited by lxdude; 02-28-2011 at 09:08 PM. Click to view previous post history.
    I do use a digital device in my photographic pursuits when necessary.
    When someone rags on me for using film, I use a middle digit, upraised.

  5. #5
    ic-racer's Avatar
    Join Date
    Feb 2007
    Location
    Midwest USA
    Shooter
    Multi Format
    Posts
    5,938
    Quote Originally Posted by pawlowski6132 View Post
    I guess I never thought of this before but, how does one focus a view camera to infinity??

    Although I'm sure the answer will be painfully obvious and I'll be embarrassed I asked, I have to ask.

    Do you need to know the focal length of your lens?
    Some folding view cameras have infinity stops. Once set, they allow you to rapidly pull the front standard out to a specific point after unfolding the camera. Some people set them just past infinity, so you can find tune the focus, if it needs to be at infinity, after you get the camera set up.

  6. #6
    lxdude's Avatar
    Join Date
    Apr 2009
    Location
    Redlands, So. Calif.
    Shooter
    Multi Format
    Posts
    6,454
    View cameras are focused by observing the image on a ground glass at the film plane, which is then removed and the holder containing the film or plate is put in its place.
    I do use a digital device in my photographic pursuits when necessary.
    When someone rags on me for using film, I use a middle digit, upraised.

  7. #7

    Join Date
    Dec 2007
    Location
    Seattle, Washington area
    Shooter
    Large Format
    Posts
    365
    Quote Originally Posted by ntenny View Post
    It'll be the exact focal length of the lens, won't it? Modulo the fact that "infinity" isn't really infinity, which should make a microscopic difference if you picked a nice distant object, and any slop in choosing your points of measurement. Am I missing something that makes it only an approximation?

    -NT
    It really is only a close approximation. I set up my Sinar Norma at infinity (by focusing on a very distant object) and measured the distance from the film plane to see where the lens focal length comes to on the lens, knowing that it's the rear nodal point that's important. I did this for different lenses and discovered that the front of the lens board was correct for all Symmars (symmetrical design), but the aperture ring was correct for all Super Angulons (unsymmetrical design). I added this fact to my field notebook so as not to forget it. So lens design is a contributing factor. Note: This technique is not valid for telephotos designs, which I do not own.



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin