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Thread: focus problems

  1. #1
    rmolson's Avatar
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    focus problems

    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. Itís 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.

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    Jon Shiu's Avatar
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    Hi, the thickness doesn't really matter, as long as the ground side of the glass is at the same position as before.

    Jon
    Mendocino Coast Black and White Photography: www.jonshiu.com

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    RalphLambrecht's Avatar
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    Quote Originally Posted by rmolson View Post
    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. Itís 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.
    Jon Shiu is correct. Are you sure you've got it on the right side?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  4. #4
    rmolson's Avatar
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    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. #5
    Rick A's Avatar
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    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



 

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