Page 5 of 7 FirstFirst ... 34567 LastLast
Results 41 to 50 of 64

Thread: Changing shutters?

  1. #41
    Andrew's Avatar
    Join Date
    Jan 2008
    Location
    Sydney, Australia
    Posts
    368

    Re: Changing shutters?

    If we're talking relative values... can I bring this onto a table top with a light source behind a diffuser and simply put the light meter on the other side of the lens?

  2. #42
    8x10, 5x7, 4x5, et al Leigh's Avatar
    Join Date
    Dec 2010
    Location
    Maryland, USA
    Posts
    5,454

    Re: Changing shutters?

    Sure. Just make sure the light is very diffuse and uniform over the viewing area.

    In fact, a defocused subject will give you more uniform illumination than a focused subject,
    unless the subject has a very uniform tone and reflectance to start with (like a gray card).

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  3. #43

    Join Date
    Dec 2001
    Location
    NJ
    Posts
    8,470

    Re: Changing shutters?

    Quote Originally Posted by Leigh View Post

    When the illumination on the GG is the same for both shutters, then the actual aperture is the same.

    - Leigh
    Think this over carefully. It works for the same cells in different shutters, not for different lenses.

  4. #44
    8x10, 5x7, 4x5, et al Leigh's Avatar
    Join Date
    Dec 2010
    Location
    Maryland, USA
    Posts
    5,454

    Re: Changing shutters?

    Quote Originally Posted by Dan Fromm View Post
    Think this over carefully. It works for the same cells in different shutters, not for different lenses.
    Of course it works for different lenses.

    That's why an exposure at f/8 will come out the same for any lens (ignoring differences in FoV).

    This is the whole basis for photographic exposure.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  5. #45

    Join Date
    Feb 2012
    Location
    South Texas
    Posts
    1,837

    Re: Changing shutters?

    I'd think it would work fine with both lenses at infinity focus.

  6. #46
    8x10, 5x7, 4x5, et al Leigh's Avatar
    Join Date
    Dec 2010
    Location
    Maryland, USA
    Posts
    5,454

    Re: Changing shutters?

    Focus point (i.e. bellows extension) is irrelevant if the two lenses have approximately the same FFL.

    Even a 10mm difference in FFL should result in <1% error (approximation) for lenses in the focal length under discussion.

    If the lenses have disparate focal lengths, then yes they should be focused at infinity for maximum accuracy.

    BTW, this does not mean that the test target/subject needs to be at infinity, as discussed above.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  7. #47

    Join Date
    Feb 2012
    Location
    South Texas
    Posts
    1,837

    Re: Changing shutters?

    If both lenses have nearly identical focal distance then, yes, bellows extension is irrelevant. No, the target need not be near infinity focus. In fact, I'd place it very near the lens(es) with them focused at approximately infinity just to blur the target.

  8. #48
    8x10, 5x7, 4x5, et al Leigh's Avatar
    Join Date
    Dec 2010
    Location
    Maryland, USA
    Posts
    5,454

    Re: Changing shutters?

    Quote Originally Posted by Old-N-Feeble View Post
    In fact, I'd place it very near the lens(es) with them focused at approximately infinity just to blur the target.
    Yep, exactly.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  9. #49

    Join Date
    Dec 2001
    Location
    NJ
    Posts
    8,470

    Re: Changing shutters?

    Quote Originally Posted by Leigh View Post
    Of course it works for different lenses.

    That's why an exposure at f/8 will come out the same for any lens (ignoring differences in FoV).

    This is the whole basis for photographic exposure.

    - Leigh
    Stuff and nonsense. Transmittance makes a difference

    Why do you think that the very serious folks in "Hollywood" use lenses with diaphragms calibrated in T/stops?

  10. #50
    8x10, 5x7, 4x5, et al Leigh's Avatar
    Join Date
    Dec 2010
    Location
    Maryland, USA
    Posts
    5,454

    Re: Changing shutters?

    Dan,

    Have you been drinking?

    T-stops are just accurate apertures, used because they want extremely accurate exposures.

    They DO NOT measure luminance at the film plane, as I've suggested for this application.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

Similar Threads

  1. Changing Copal Shutters To Prontor Professional
    By bartbartolomeo in forum Lenses & Lens Accessories
    Replies: 2
    Last Post: 11-Feb-2012, 09:54
  2. changing bag vs. changing tent
    By Harley Goldman in forum Gear
    Replies: 18
    Last Post: 22-Dec-2005, 16:50
  3. LCD shutters - any experience? 4x5 FP shutters?
    By bglick in forum Lenses & Lens Accessories
    Replies: 16
    Last Post: 14-Aug-2005, 08:09
  4. Changing Shutter Speeds in Charged Copal Shutters: Fact & Fiction
    By Paul Chaplo in forum Lenses & Lens Accessories
    Replies: 6
    Last Post: 30-Oct-2001, 09:39

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
  •