Page 1 of 2 12 LastLast
Results 1 to 10 of 17

Thread: Measuring thread size.

  1. #1
    Kirk Gittings's Avatar
    Join Date
    Mar 2004
    Location
    Albuquerque, Nuevo Mexico
    Posts
    9,746

    Measuring thread size.

    This is probably a no brainer, but not for me. I have an old B&L petzval that I want to put ND filters on to slow down the exposure. So I'm looking to buy a step up adapter. Do you just put the caliper on the inside measure the inside diameter and the reading you get is the size?
    Thanks,
    Kirk

    at age 68
    "The woods are lovely, dark and deep,
    But I have promises to keep,
    And miles to go before I sleep,
    And miles to go before I sleep"

  2. #2
    8x20 8x10 John Jarosz's Avatar
    Join Date
    May 2006
    Location
    Fairfax Iowa
    Posts
    648

    Re: Measuring thread size.

    Threads are spec'ed by measuring the outside diameter of a male thread. So if you are measuring the ID of the female thread, then I would add .060 (.030 per side) to your measured diameter. This will give you a starting point. Plus, you don't know the pitch of the thread yet (Threads per inch). Is this an old lens? Maybe if you say what lens it is someone here may already know.

  3. #3
    Kirk Gittings's Avatar
    Join Date
    Mar 2004
    Location
    Albuquerque, Nuevo Mexico
    Posts
    9,746

    Re: Measuring thread size.

    Thanks. Its an old (not super old) B&L Projector lens.
    Thanks,
    Kirk

    at age 68
    "The woods are lovely, dark and deep,
    But I have promises to keep,
    And miles to go before I sleep,
    And miles to go before I sleep"

  4. #4
    8x20 8x10 John Jarosz's Avatar
    Join Date
    May 2006
    Location
    Fairfax Iowa
    Posts
    648

    Re: Measuring thread size.

    It may also be Imperial threads rather than metric, which is what most step up rings are. You may be faced with simply going to a store so you can try on rings and use what fits. Or, you may have to kludge a square filter holder that could be attached to the outside of the barrel.
    Last edited by John Jarosz; 29-Mar-2012 at 11:23. Reason: left some words out

  5. #5
    Format Omnivore Brian C. Miller's Avatar
    Join Date
    Jun 1999
    Location
    Everett, WA
    Posts
    2,960

    Re: Measuring thread size.

    You can make your own filter adapter, if the lens has enough thread on the end of it.

    Use a ruler to get a basic measurement. Then buy a cheap filter a bit smaller, and take out the glass. Wrap a bit of plastic or rubber tape on the thread edge, just enough to give the threads on the lens some bite, and gently screw it in. Now you have a standard filter size you can use to screw something else into it.
    "It's the way to educate your eyes. Stare. Pry, listen, eavesdrop. Die knowing something. You are not here long." - Walker Evans

  6. #6

    Join Date
    Sep 1998
    Location
    GA
    Posts
    12,382

    Re: Measuring thread size.

    Is this the lens brom the B&L that accepted single 2 1/4 slides as well as tray fed 35mm slides? I believe that one had an adjustable diaphragm on it to adjust brightness. But it has been so long since I handled one, late 50s early 60s, that I don't remember the lens having screw threads.

  7. #7
    Kirk Gittings's Avatar
    Join Date
    Mar 2004
    Location
    Albuquerque, Nuevo Mexico
    Posts
    9,746

    Re: Measuring thread size.

    Thanks Brian. Thats a great idea.

    Bob, hell if I know, but I think its a movie projector lens. it says B&L Cinephor Series 1 on it. It is a chrome barrel and black cellover brass so not that old-uncoated though.
    Thanks,
    Kirk

    at age 68
    "The woods are lovely, dark and deep,
    But I have promises to keep,
    And miles to go before I sleep,
    And miles to go before I sleep"

  8. #8
    Kirk Gittings's Avatar
    Join Date
    Mar 2004
    Location
    Albuquerque, Nuevo Mexico
    Posts
    9,746

    Re: Measuring thread size.

    So I get 46.59 on the inside so adding .060 gives me 47mm ish. No such animal out there right?
    Thanks,
    Kirk

    at age 68
    "The woods are lovely, dark and deep,
    But I have promises to keep,
    And miles to go before I sleep,
    And miles to go before I sleep"

  9. #9

    Join Date
    Sep 1998
    Location
    GA
    Posts
    12,382

    Re: Measuring thread size.

    Different lens.

  10. #10

    Join Date
    Sep 1998
    Location
    GA
    Posts
    12,382

    Re: Measuring thread size.

    Heliopan makes 46 and 48mm filters. Why not measure the outside diameter and see if a 48 or 49mm would slide over it tightly enough? If necessary a layer of tape or Velcro loop material might make it a tight enough fit.

Similar Threads

  1. measuring aperture opening
    By Roger Vadim in forum Lenses & Lens Accessories
    Replies: 6
    Last Post: 29-May-2011, 05:40
  2. measuring beakers
    By Jim C. in forum Darkroom: Film, Processing & Printing
    Replies: 10
    Last Post: 13-Aug-2009, 13:21
  3. Measuring Film Density
    By ageorge in forum Darkroom: Film, Processing & Printing
    Replies: 16
    Last Post: 8-Dec-2006, 08:22

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •