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  1. #1
    Member
    Join Date
    Sep 2004
    Location
    invercargill
    Posts
    10

    spot before my eyes

    Hi have a wide angle lens that shows small black round/oval marks when camera is on very close focus. I know it is the lens because they move when I unscrew lens from the camera. In low light conditions the autofocus picks up on these spots before the subject. I can't see any marks on the lens. Any ideas or is this just flaws in a cheap(ish) lens?

    Thanks John

  2. #2
    John,


    One of my employees came to me with the same problem the other day. With out being there and looking at your lens, i can not tell you exactly what it is, however the problem here was that he was using a clear lens filter and the lens was seeing its self reflecting off the filter. I am not sure if you are using a attachable filter, but if you are, take it off and see if that is the problem.

    hope this helps

    RJ
    Manoni Productions
    Pass me another beer...You are still ugly!

  3. #3
    Hey John.
    Do you actually see the spots in the lens as you shoot, or do they only show after taking the image?

    I was inclined to agree that you're getting reflection from filter to lens, Except - I've only noticed that problem myself with high contrast shots - like getting a 'double' image of the bright moon at night, as it reflects from filter to glass. And I see bright spots, not black.

    Lenses, cheap or otherwise, are not the airtight vaults we want to think - dust and dirt can invade the glass at any time - chance of that increases over time and with adverse conditions like humidity, dust, extreme temperatures.

    My real guess is that you just have dirt on your digital sensor - ccd. That is enough to grind your autofocus down to dust, as its constantly fooled by the crud it sees.

    To summarize, I think you have dust and dirt somewhere - on the ccd or perhaps the lens - but I agree that shooting without that filter is the best way to start the investigation. Thanks John and good luck!

    eyepatch

  4. #4
    Member
    Join Date
    Sep 2004
    Location
    invercargill
    Posts
    10

    internal dust

    A closer examination of the lens with a flashlight has revealed some internal dust. The camera seems to be able to focus past this without noticeable degradation of the image. Guess I will have to live with it or get the lens serviced. Thanks for help guys.

  5. #5
    I would advise getting the lens cleaned. If the dust is in the inside, those glass pieces are not as tough as the ones on the outside, even a little dust could scratch the glass on the inside. believe me it is cheaper to get it fixed then have to buy a new one.
    Manoni Productions
    Pass me another beer...You are still ugly!

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