focus problems

Discussion in 'Large Format Cameras and Accessories' started by rmolson, Sep 25, 2009.

  1. rmolson

    rmolson Member

    Messages:
    307
    Joined:
    Feb 23, 2006
    Location:
    Mansfield Oh
    Shooter:
    Medium Format
    Focus


    Having a problem with ground glass. Got a fine ground glass for my 4x5 press view. I replaced the old glass which was a coarser grain .But now my images seem ever so slightly soft as though I missed in focusing with my magnifier. Dug out an old micrometer and checked thicknesses. It’s been so long since I worked with a micrometer and I probably have the wrong readings but there is a difference between the glass the old read about .013 and new glass .005. It is only a tiny difference if my measurements make no sense But would it be enough to throw my focus off a hair?
    I have a 150mm F/5.6 Topcor which gave me good results on my monorail,but I can't carry that into the field.
     
  2. Jon Shiu

    Jon Shiu Subscriber

    Messages:
    2,796
    Joined:
    Dec 2, 2003
    Location:
    Elk, Califor
    Shooter:
    Plastic Cameras
    Hi, the thickness doesn't really matter, as long as the ground side of the glass is at the same position as before.

    Jon
     
  3. RalphLambrecht

    RalphLambrecht Subscriber

    Messages:
    7,802
    Joined:
    Sep 19, 2003
    Location:
    Central flor
    Shooter:
    Multi Format
    Jon Shiu is correct. Are you sure you've got it on the right side?
     
  4. rmolson

    rmolson Member

    Messages:
    307
    Joined:
    Feb 23, 2006
    Location:
    Mansfield Oh
    Shooter:
    Medium Format
    I checked that part ,next I suppose will be to check if the film plane and the ground glass agree.the camera while all metal is 50 years old and I suppose something could have changed since then.
     
  5. Rick A

    Rick A Subscriber

    Messages:
    7,289
    Joined:
    Mar 31, 2009
    Location:
    northern Pa.
    Shooter:
    Multi Format
    I havent used a LF in some time, but could it be just the difference in contrast between the fine and coarser glass? Just a thought.
    Rick