Page 1 of 2 12 LastLast
Results 1 to 10 of 11

Thread: Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture question

  1. #1
    Apo-Heespharm-N MC
    Join Date
    Oct 2010
    Location
    houston
    Posts
    191

    Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture question

    How do I determine the aperture adjustment?? Spot meter on ground glass? Measure the amount of light falling on the ground glass?

  2. #2

    Join Date
    Dec 2001
    Location
    San Joaquin Valley, California
    Posts
    9,082

    Re: Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture questi

    See if Calumet can supply you with a scale?
    I steal time at 1/125th of a second, so I don't consider my photography to be Fine Art as much as it is petty larceny.
    I'm not OCD. I'm CDO which is alphabetically correct.

  3. #3

    Join Date
    Dec 2001
    Location
    NJ
    Posts
    7,871

    Re: Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture questi

    Open the diaphragm as wide as it will go. Close it slowly. The marked stop at which it just becomes visible through the front element corresponds to f/9.

  4. #4
    Apo-Heespharm-N MC
    Join Date
    Oct 2010
    Location
    houston
    Posts
    191

    Re: Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture questi

    Quote Originally Posted by Dan Fromm View Post
    Open the diaphragm as wide as it will go. Close it slowly. The marked stop at which it just becomes visible through the front element corresponds to f/9.
    After that how do I determine the other fstops?

  5. #5

    Join Date
    Dec 2001
    Location
    NJ
    Posts
    7,871

    Re: Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture questi

    f/11 is 1/2 stop down from f/9. f/16 is 1 stop down from f/11. And so on.

    The scale marks are spaced 1 stop apart. Once you've found the mark that corresponds to f/9 you're set. Except that you should know this already.

  6. #6

    Join Date
    Dec 2000
    Location
    Tonopah, Nevada, USA
    Posts
    6,338

    Re: Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture questi

    Your old scale is usable but it's 1/3 stop off at every stop. ie. when it says you're at f11, slide the aperture 1/3 stop back towards f8, and this is your new f11. One possibility is to elongate the holes in the scale so you can re-attach it in the correct place for the numbers to work. Or simply try to remember to always open a 1/3rd of a stop. Recipe for disaster playing these memory games for most of us, but it's only a 1/3 stop.

  7. #7
    Apo-Heespharm-N MC
    Join Date
    Oct 2010
    Location
    houston
    Posts
    191

    Re: Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture questi

    Quote Originally Posted by Dan Fromm View Post
    f/11 is 1/2 stop down from f/9. f/16 is 1 stop down from f/11. And so on.

    The scale marks are spaced 1 stop apart. Once you've found the mark that corresponds to f/9 you're set. Except that you should know this already.
    I didn't know that the spacing between fstops is the same no matter what elements your using...

  8. #8

    Join Date
    Dec 2001
    Location
    NJ
    Posts
    7,871

    Re: Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture questi

    Think about the meaning of f/ numbers and you'll see why.

  9. #9

    Join Date
    Jul 1998
    Location
    Lund, Sweden
    Posts
    2,209

    Re: Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture questi

    If it's an original, plain Sironar the aperture scale will be even closer to correct than the 1/3 of a stop that Jim calculated. The switch from the asymmetric Sironar to the symmetric G-claron almost cancels out the focal length change, at least in a back of the envelope calculation. I get just under 1/5 of a stop less exposure for the G-claron.

    The difference is more easily measured than calculated. If you have a meter with a ground glass probe attachment, you can compare readings for the two lenses with the camera pointed at a stable light source which fills a reasonable area of the ground glass when in focus. Otherwise, you can take a photo of a greyscale with each lens and compare densities.

    I always overexpose negative film by a stop or so, so were it me, I would just get on with using the lens with the existing aperture markings. Add a half stop later if the negs look a little anaemic.

  10. #10

    Join Date
    Nov 2009
    Location
    Sheffield, UK.
    Posts
    574

    Re: Mounted 240 g clarion elements in my sironar 210mm copal shutter..aperture questi

    Quote Originally Posted by Dan Fromm View Post
    f/11 is 1/2 stop down from f/9. f/16 is 1 stop down from f/11. And so on.

    The scale marks are spaced 1 stop apart. Once you've found the mark that corresponds to f/9 you're set. Except that you should know this already.
    This assumes that the shutter has stops spaced in a linear fashion - I know some older Compurs dont (more spread out at the wide open end) in which case its a bit trickier. But if its a linear scale you're laughing.

    I use a 150mm g claron in a shutter from a 150mm symmar-s. As someone else said, find the point that its just stops being wide open and this is your F9 point, everything else should then fall into place assuming a linear aperture shutter. In my case all the stops were about a stop less than on the scale (i.e. f32 on the g claron is about the same diameter as f45 on the symmar, presumably some quirk of lens design).

Similar Threads

  1. remounting Fujinon 5.6/105 NW in new Copal 0 shutter question
    By Arne Norris in forum Lenses & Lens Accessories
    Replies: 6
    Last Post: 21-Sep-2008, 08:28
  2. Remounting a Lens to a Copal #1 Press Shutter
    By Yuriy "D" in forum Lenses & Lens Accessories
    Replies: 3
    Last Post: 20-Nov-2006, 09:41
  3. Sinar Shutter - f/4 versus f/5.6 and Cables ?
    By Frank Petronio in forum Cameras & Camera Accessories
    Replies: 4
    Last Post: 8-Nov-2006, 05:59
  4. 240 G-Claron & Copal Shutter size...
    By Capocheny in forum Lenses & Lens Accessories
    Replies: 2
    Last Post: 15-Jul-2006, 00:02

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
  •