Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,694   Posts: 1,549,020   Online: 908
      
Page 3 of 3 FirstFirst 123
Results 21 to 27 of 27
  1. #21

    Join Date
    Feb 2012
    Location
    Nova Scotia, Canada
    Shooter
    Medium Format
    Posts
    289
    Quote Originally Posted by AgX View Post
    As the film is not in contact with the image frame, there must be a point light source, or at least rays that are focused at the film plane to cause sharp borders.
    If the baffle had a leak then whilst handling there would be the effect of diffuse exposure.
    so maybe it is flare then? but wouldn't flare also not cause the sharp border?

  2. #22
    erikg's Avatar
    Join Date
    Feb 2003
    Location
    pawtucket rhode island usa
    Shooter
    Multi Format
    Posts
    1,409

    Is there something wrong with this colour negative?

    Sounds very possible, and that would explain the offset.

  3. #23

    Join Date
    Feb 2009
    Shooter
    Large Format
    Posts
    665
    I examined my RZ67 Pro II back assuming that it’s similar to the RB67 back. When viewing the film opening with the dark slide removed, it’s easy to see that the pressure plate is about a 1.5mm deeper than the deepest edge of the short ends of the film aperture. That provides plenty of clearance for light projected at an angle to pass under the ends of the film aperture and strike the film beyond the usual frame boundary at the ends of the frame.

    When image-forming light from the lens is projected back through the film aperture, the maximum angle that light can travel from the rear lens element passes through the aperture and defines the image rectangle on film. This is always about then same size due to the same (or nearly the same) projection angle of the various lenses that fit the camera.

    But in the case of spill light reflecting from the interior of the mirror box past an out-of-position light baffle, the light can travel from the sides of the mirror box past the edge of the baffle obliquely to pass under the ends of the film aperture due to the 1.5mm clearance between the end of the film aperture and film lying against the pressure plate.

    The source of the light is most likely from the lens to the mirror to the focusing screen. Some of the light that strikes the focusing screen must reflect and spread sufficiently to slightly illuminate the interior of the mirror box during viewing. Normally this is no problem if the light baffle is sealing the opening to the film holder as the designer intended. But if the baffle is not fully closed, then some light from the mirror box can bleed thorough the gap between the baffle and the chamber to expose the film—including a small area beyond the usual border due to the clearance mentioned. And, since the light still grazes the edge at the end of the film aperture, this would account for the sharp boundary, even into the area beyond the usual frame boundary.
    Last edited by Ian C; 10-27-2012 at 03:38 PM. Click to view previous post history.

  4. #24
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,067
    Images
    65
    Ian;

    Your explanation is without film in the back. With film in the back, that 1mm difference is taken up by the thickness of the film due to the pressure the plate exerts. Or, did I misunderstand you?

    PE

  5. #25
    polyglot's Avatar
    Join Date
    Jun 2009
    Location
    South Australia
    Shooter
    Medium Format
    Posts
    3,285
    Images
    12
    I just had a look at my RZ back and there's a good 4mm between film gate and pressure plate; plenty of room to have an offset between flare and image. I can also report that I get offset-flare (on two different RZ bodies) just like you've reported when shooting strongly-backlit scenes*, so it's not a fault with just your body. My guess is that there might be something small and reflective on the back of the mirror and that if that is illuminated during exposure then you get flare.

    And it's clearly not a problem with the baffle - the sharpness of the flare image shows that it was formed only while the shutter AND baffle were open, i.e. during exposure. If it was light leakage during handling, the flare would be spread around due to camera motion.



    * with the sun in-frame, you don't see the offset because the sun-image is on the film, so you just get lens-flare. This problem occurs with the sun only just out of frame, which causes it to illuminate the inside of the body. My scanner (Nikon 8000) doesn't really go outside the frame boundary because of how the holder works (and I tend to crop out the unevenly-flared edge-bits before saving!), so I can't easily show you an example. But this is IMHO normal behaviour for an RZ/RB.

  6. #26

    Join Date
    Feb 2012
    Location
    Nova Scotia, Canada
    Shooter
    Medium Format
    Posts
    289
    interesting. thanks for your help everyone. I am still wondering - the foggy area is offset from the image which clearly means the unwanted light is coming in at a more extreme angle than the light from the lens. This makes sense vertically, as the fog does not extend to the top of the image, and extends beyond the bottom.

    However, it is wider than the image area on both sides, which would mean that light is coming at an extreme angle from two different directions but creating a fogged area with a uniform (and sharp) top and bottom border. Can that be explained by flare?

  7. #27
    AgX
    AgX is offline

    Join Date
    Apr 2007
    Location
    Germany
    Shooter
    Multi Format
    Posts
    8,675
    I assume flare light to be multiple reflected and not fulfilling the requirements I put up in my post above.

Page 3 of 3 FirstFirst 123


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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