Dust in Lens...

Discussion in 'Digital Photography' started by TekSupport, Oct 27, 2008.

  1. TekSupport macrumors newbie

    Joined:
    Jul 9, 2008
    #1
    while lookin down into my Canon 70-200 F2.8 Lens after a recent photo-shoot afternoon..I noticed there is a speck of dust inside. WTH? Is this normal? I dont' see it on any of the shots I take...just wonderin if I should just go ahead and send it into Canon for a through cleanin.? :confused:

    Thanks !


    TS
     
  2. anubis macrumors 6502a

    Joined:
    Feb 7, 2003
    #2
    Most zoom lenses that externally extend and retract create some form of air suction that can suck dust into the inside of the lens barrel. It's rarer for better-built lenses like L-series but clearly not impossible.

    Only surfaces that are on or near intermediate image planes show up in the final image plane. Someone correct me if I'm wrong but I'm pretty sure most consumer camera lenses don't have intermediate image planes. Hence, dust and imperfections on any of the lenses won't really be visible in the final image (but could still cause a bit of general cloudiness on account of the imperfection being very "out of focus"). This is why dirt on the hot mirror shows up in your images - because the hot mirror is very close to the image plane.

    I wouldn't send it in for cleaning unless there is a clear adverse effect on image quality
     
  3. ChrisA macrumors G4

    Joined:
    Jan 5, 2006
    Location:
    Redondo Beach, California
    #3
    It's really common. The dust will not show in the image because it is NOT on one of the image planes. Try taking an old filter and drawing on it with a Sharpe, it will not show either because the filter is GROSSLY out of focus. The dust is too and the picture of the dust speck is spread out all over the frame. The "damage" the speck does it proportional to it's square area divided by the square area of the lens. I small number, I assume.

    How does it get in there? Does the lens change it's length when you zoom or focus? If so then it acts like an air pump.

    Cleaning will not do much, more will just get in later.
     
  4. apearlman macrumors regular

    Joined:
    Aug 8, 2007
    Location:
    Red Hook, NY
    #4
    Worry about something more important.

    If it doesn't show up in pictures, I wouldn't do anything to it.

    If the images are affected, clean the lens. Otherwise, don't mess with it. Remember, photo equipment = tools. If they work, they work.
     
  5. ChrisA macrumors G4

    Joined:
    Jan 5, 2006
    Location:
    Redondo Beach, California
    #5
    A zoom lens like that is very complex, so who knows but even if there were an intermediate image plane, the chance of the plane being on the surface of a element is about nill.
     
  6. Phrasikleia macrumors 601

    Phrasikleia

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    Feb 24, 2008
    Location:
    Over there------->
    #6
    My husband has a vintage lens with a lot of dust in it--very visible if you look through the lens with your eye while it's off of the camera. However, none of that dust seems to register in any of the photos, not in the least. I wouldn't worry about it at all.
     
  7. TekSupport thread starter macrumors newbie

    Joined:
    Jul 9, 2008
    #7
    very cool..thank you guys for the responses..!
    Yea...so far..haven't seen it affect any of the shots...
    Will keep an eye on it and any more that might pop up.

    Thanks again!

    btw..I luv my lens! :D


    TS
     
  8. Westside guy macrumors 601

    Westside guy

    Joined:
    Oct 15, 2003
    Location:
    The soggy side of the Pacific NW
    #8
    Lens dust usually isn't sucked in from the outside - it's little pieces produced by wear due to the mechanical activities going on inside your lens (aperture blades rubbing against each other, gears turning, etc.). As long as there's not so much present that it affects image contrast, it's generally not a concern.

    If you ever see strands inside a lens, though, that's not dust - it's fungus, and it's a bad thing.
     
  9. TekSupport thread starter macrumors newbie

    Joined:
    Jul 9, 2008
    #9
    Uh..fungus? what would cause that? well..other than moisture I suppose...


    TS
     
  10. Phrasikleia macrumors 601

    Phrasikleia

    Joined:
    Feb 24, 2008
    Location:
    Over there------->
    #10
    Yup. A very bad case of it would look like this:

    [​IMG]

    :eek::eek::eek:
     
  11. Westside guy macrumors 601

    Westside guy

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    Oct 15, 2003
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    #11
    ^ ^ ^ ^ That was funny and gross at the same time... :p
     
  12. uptherighttree macrumors member

    Joined:
    Jun 16, 2008
    #12
    my tamron lens had to be sent off. it was tolerable for 99% of shots but when i did high key product shots one spot would always show up in key areas of the product.

    could shop it but that was getting annoying. Sent it away to get it cleaned and only cost £41
     
  13. apearlman macrumors regular

    Joined:
    Aug 8, 2007
    Location:
    Red Hook, NY
    #13
    Shoot it!

    Wow, unbelievable! Okay everyone, quick quiz:

    You've just discovered an entire mushroom growing inside one of your lenses. What is your response?
    a) Ewww, gross! Throw it away!
    b) Wow, cool! Wonder what the inside looks like! I'll take it apart.
    c) Amazing! Let me put it in my light tent and shoot some photos of it!

    You might be a photographer if you answered "c". (Of course, I hope the next act was to throw it far, far away. Fungus can be contagious.)
     
  14. wheelhot macrumors 68000

    Joined:
    Nov 23, 2007
    #14
    Yeah, it will be nice to see what kind of image will be produced with a fungus growing in the lens and at the same time Its ewwwww :p
     
  15. chiefroastbeef macrumors 6502a

    Joined:
    May 26, 2008
    Location:
    Dallas, Texas/ Hong Kong
    #15
    Maybe it'll be a new artform!

    I too have a bunch of dust right under my Nikkor 18-200mm lens. It is under the first piece of glass, and quite annoying considering it wasn't a cheap lens.
     
  16. Westside guy macrumors 601

    Westside guy

    Joined:
    Oct 15, 2003
    Location:
    The soggy side of the Pacific NW
    #16
    It has absolutely nothing to do with how cheap or expensive the lens is. It's more a sign of a well-used lens than anything else.
     

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