Polarizing Filter on Ground Glass

Discussion in 'Large Format Cameras and Accessories' started by Lobalobo, Sep 8, 2009.

  1. Lobalobo

    Lobalobo Member

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    Just shot a beach scene using an old Graflex 4x5 camera and a Fujinon 125mm lens. The sun was in perfect place for a polarizing filter and when I held the filter to the naked eye, aimed at the scene, and rotated it, I easily saw variations in the effect of the filter. In the ground glass of the camera, though, I could see no effect from rotating the filter (or almost no effect). Eventually, I just took the position of the filter held to my eye and put it on the camera in that position, hoping for the best. Am I just seeing things (or in this case not seeing things) or does the ground glass not show the polarizing effect?
     
  2. archphoto

    archphoto Member

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    The lens rotates the image 180 degrees onto your GG.

    Have you tried to apply this ???

    Peter
     
  3. Lobalobo

    Lobalobo Member

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    As I said, I rotated the filter, of course. Not sure what you meant by the lens rotating the image 180 degrees. In any case, a private message let me know that ground glass is too dim to notice effect of filter and that the technique I used was the standard one. So thanks for that.
     
  4. AndersPS

    AndersPS Member

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    I´ve read somewhere that a polarizing filter works best if you have the sun 45 or 90 degrees behind you. But I could be wrong!
     
  5. Lobalobo

    Lobalobo Member

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    Yes, I'm pretty sure that the filter works in a 90 degree arc from a straight line drawn from where the camera is standing to the sun (so if the sun rises due east, at dawn, the filter's effect is greatest shooting due north or due south). My problem was not in with the filter or the position of the sun, but with the fact that the effects of the filter were not visible in the ground glass. I couldn't figure out whether I was going blind or crazy, but I've been informed (in a private email response to my post) that I was not, that in fact the glass is not bright enough to show the difference. So I was doing the right thing all along, I guess. I had used a polarizing filter on digital cameras before, and saw the changes from rotating the filter even in an electronic viewfinder, so I was surprised.
     
  6. Peter De Smidt

    Peter De Smidt Member

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    Hm. A few months ago I used a polarizer on my 4x5 quite a bit. I could see the sky darken on the ground glass as I rotated the polarizer. It probably depends a lot on the scene, lens and type of ground glass. I was using a 210mm F5.6 lens with a Toyo screen.
     
  7. Lobalobo

    Lobalobo Member

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    That's useful. I'm using a Graflex, which is, if I'm not mistaken, a 50 year old press camera not designed, I'd wager, to be used with polarizing filters. (In fact, I'll bet most owners used the camera with a rangefinder and skipped the ground glass altogether.) The glass is thick and dim, generally. So maybe what I really need is a true view camera.
     
  8. Sirius Glass

    Sirius Glass Subscriber

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    And the GAS begins!

    Steve
     
  9. Lobalobo

    Lobalobo Member

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    What does this mean?
     
  10. Peter De Smidt

    Peter De Smidt Member

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    "GAS" means Gear Acquisition Syndrome. But I don't think you need a new camera. First, try cleaning the ground surface of your ground glass. Dish soap works. (Take the groundglass off of the camera. Put a little soap and water on it. Rub a little bit with a soft sponge, and rinse under running water. Let dry. Make sure to install it with the ground surface facing the lens.) If that doesn't do it, you can get a replacement ground glass.
     
  11. Lobalobo

    Lobalobo Member

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    Wow, I'm using a 60 year-old press camera as a substitute for a view camera, with a 35 year old lens, and so would have thought I'd be immune to gear acquisition syndrome. In any case, thanks for the advice but I'm hesitant to remove anything from this Graflex for fear it won't go back on. For example, the viewfinder on top is broken but frozen in place; I can't remove it though I want to (as it's useless). I worry that the glass will break if I try to remove it to clean it. I think I'll stick with my current method, which is to estimate the position of the filter by holding it up to my face and rotating until I get the effect I want, then place it on the camera replicating that position. Is there any downside to this, save lack of precision, which isn't great in any case for me?
     
  12. Tom Nutter

    Tom Nutter Member

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    I can't see a problem with that...Someone mentioned earlier that the image is rotated 180 degrees by the lens, which is why it is upside-down on your ground glass, but correct me if I'm wrong somebody, that amazing feat of physics occurs after the light has passed through the filter on the front of the lens. Logic tells me that everything that occurs in front of the lens will be flipped when it reaches the ground glass, including the polarizing effect. What a strange thing to think about!

    Oh, and are you composing with your head under a dark cloth? Keeping things as dark as possible makes it easier to see what is happening on the glass.
     
  13. Jim Noel

    Jim Noel Member

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    The brand of camera has nothhing to do with the effect of any filter.
    A polarizer has the most effect when the sun is at 90 degrees to the lens. Rotate the filter until th indicator points at the sun for the strongest effect.
     
  14. Tom Nutter

    Tom Nutter Member

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    Also, an addendum to the other thing I said....make sure you are holding the filter in front of your eye the same way as it fits on the lens....I.E.---with the threads toward your eye, as if they were mounting to the lens.:smile:
     
  15. Nicholas Lindan

    Nicholas Lindan Advertiser

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    Were you looking at the ground glass through the filter or at the ground glass with the filter mounted on the lens?

    The lens will have nothing to do with the effect of the filter if the filter is mounted in front of the lens. And you would have to have a pretty bizarre lens if it had any effect with the filter mounted behind the lens.

    The viewing hood on a Speed Graphic isn't light-tight and the effect of the polarizer you will see in the ground glass will be diminished by the stray light falling on the ground glass. For really examining the ground glass you need a black-out cloth or a binocular viewing hood.