To clean, or not to clean, the pentaprism?

Discussion in '35mm Cameras and Accessories' started by melmoth, Oct 16, 2005.

  1. melmoth

    melmoth Member

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    Hallo,

    Maintenance Question:

    I have a speck of something which is visible inside, on the pentaprism when the lens is off. Invariably, it appears in the viewfinder window when taking pictures.

    I have tried to remove with air or a light brush but it refuses to budge.
    Someone told me that it was inadvisable to interfere with a pentaprism as they are very sensitive. Better to send it away to be cleaned.

    Can I do this myself? The camera in question is a minolta dynax 5.

    Many thanks for any help,

    M.
     
    Last edited by a moderator: Oct 16, 2005
  2. melmoth

    melmoth Member

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    Everything that goes into a saltmine, eventually becomes salt.
     
  3. resummerfield

    resummerfield Subscriber

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    If you are certain it is appearing on the negative, it is not in the pentaprism. If the speck appears focused or sharp, check in the area of the film plane. If it truely is in the pentaprism, leave it alone.
     
  4. Dave Parker

    Dave Parker Inactive

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    If it was in the prism, it would not show up on the negative, if you have spots on the negs, they something is behind the mirror in the light path to the film.

    Dave
     
  5. melmoth

    melmoth Member

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    Thanks guys.

    I amended the entry.
     
  6. wildbill

    wildbill Member

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    The guy i bought my Pentax 67II from must have cleaned the hell out of the mirror on numerous occasions because it's scratched all to hell. Leave it.
     
  7. haris

    haris Guest

    I would not touch pentaprism by myself. Mirror too.

    Melmoth, light goes through lens directly on film. In moment of exposing mirror is up, freeing path for light to hit film, and close path to pentaprism. So, no dirt on pentaprism or mirror will be produced on film. Dirt on mirror and pentaprism can make problems with autofocusing or light mettering, but will not be shown on film. Dirt on film can be produced by dirt on lens (but as I know lens dirt or scratches make photograph to be soft or can produce flare, I think it is rare that lens dirt will be clear sharp shown on negative) or by dirt inside of camera, for example hair. Check light path from lens to film. And check if pressure plate of camera is clean.

    Of course negative can be dirt by itself (manufacturing errors, wrongly storage or handling, dirt can fall on film during develping (processing) or driyng of film in dirty enviroment, etc...).
     
  8. melmoth

    melmoth Member

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    Thanks for that.

    Nicely explained.
    The consenus would suggest that if the mark does not appear on the negative film then leave the pentaprism alone or risk damage to it by cleaning.
    I will leave it.
    However, out of interest, supposing one did get a speck of dirt on the underside of the pentaprism and it affected the view, to the point where it became a hinderence. On one's own, how could you remove this - presuming it did not respond to air or a light brush? Not that I will try, but someone must have been forced to attempt this before - no?
    Most curious. M.
     
  9. Dave Parker

    Dave Parker Inactive

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    Melmoth,

    Many of the Minolta cameras over the years have removable viewing screens, I don't know on the 5, but I know on my 8000i, 7XI and my 9XI's as well as my Maxxum 9 if I get dirt in the prism, I can remove the screen and lightly, and I mean very lightly use canned air with light bursts of air, and normally dislodge the dirt, if you do this, take in mind, that you need to be very careful, do not invert the can of air, as you will end up with propellent being discharge with the air, which can damage mirrors and prisms.

    If the 5 does not have a removable screen you would have to send it to the repair shop to have them clean it, but in the many years I have shot, I have never seen so much dirt in a prism to actually cause metering and AF problems.

    Dave
     
  10. melmoth

    melmoth Member

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    Food for thought. Thanks, Dave.
     
  11. sajianphotos

    sajianphotos Member

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    I don't have a Minolta but I had some kind of bug larvae show up in my Nikon FTn finder some time ago. Though it didn't interfere with the view or focus it bugged (pun intended) the heck out of me until I finally dug into it. I'm fairly mechanical mind you. Ended up buying a new (used) finder. IMHO unless the camera is unusable and you have step by step instructions leave it alone.
     
  12. John Koehrer

    John Koehrer Subscriber

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    For what it's worth, a prism surface or front surface mirror can be cleaned of stubborn dust with a feather usually contributed by a duck or goose. Voluntarily or not.
    I will shave the feather down so it has only one edge about 3/8" long on one side of the tip of the feather. Clean it with rubbing alcohol to remove the natural oils in it before you use it or you'll end up cleaning oil off the surface too.
    If whatever is on the prism or mirror doesn't come off with this tool I'd leave it alone.