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Dust, fungus etc. in lens

Discussion in 'Lens Matters' started by Malcolm_Stewart, Mar 10, 2019.

  1. Malcolm_Stewart

    Malcolm_Stewart Well-Known Member

    Yet again I've seen an advert for a lens which says that the dust, fungus etc. has no effect on the image.

    Have any of us had a trade-in price reduced by an eagle eyed shop assistant, only to see "our" lens advertised a few days later at top price?

    I know that occasionally I've been horrified by what I've seen when shining a light through a "clean" lens. (My Focotars are definitely more dusty than other reputable enlarging lenses in my collection. I have wondered if Leitz used more internal blackening than say Nikon, Schneider, Rodenstock etc. and that it's fallen off over the years.)
  2. PeteRob

    PeteRob Well-Known Member

    In the case of dust it's all a matter of degree but I wouldn't leap to buy a lens with fungus. That said, the only one I have seen was when I bought an entire used outfit to replace mine that had been stolen, and the 50 mm was so bad you couldn't really see through it.
  3. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    I've bought dusty lenses in the past. Typically I paid a half to two thirds the normal price. None of these "sub-standard" lenses failed to please me. ;)
    peterba likes this.
  4. GeoffR

    GeoffR Well-Known Member

    All lenses breathe, it is inevitable if you move elements about, as is the case when focusing, you will change the internal volume. If the internal pressure is not going to fall air must enter somewhere and that air will inevitably contain some dust. Most of the air will come from inside the camera and, in the days of film, that was a great source of particulates generated by the movement of film, shutter, mirror etc. Without the film as a dust source I suspect some more modern lenses suffer somewhat less from dust, even so some is inevitable.

    Fungus on the other hand isn't inevitable but once it starts it will only get worse unless it is treated. Sometimes the cure is more expensive than replacing the lens but where that isn't possible cleaning can be performed by disassembly. Not something to try at home!

    I have a Nikon 180 f2.8 with a significant mark on the front element, it makes no difference to the final images, though I have never tried using it in conditions where flare might become an issue. Dust will have even less effect, unless it is sufficient to reduce light transmission.
  5. IvorETower

    IvorETower Little Buttercup

    The major reason why I wouldn't buy a used lens that had fungus.
  6. John Farrell

    John Farrell Well-Known Member

    I've bought many lenses with dust or fungus in them. Some I've sucessfully cleaned. A few years ago I bought 2 x 58mm F2 Biotar lenses, with some old Praktica cameras. They each had marks on the coating of one of their elements from fungus. I polished the marks out with toothpaste, and I've used both lenses - they work fine.
    peterba likes this.
  7. nimbus

    nimbus Well-Known Member

    A bit of dust doesn't bother me, fungus induces paranoia!
  8. Petrochemist

    Petrochemist Well-Known Member

    Unless there's a huge amount of it neither dust or fungus will make a noticeable difference to most of the images a lens produces, but both will affect the lenses value. Sometimes traders will only knock £5 off their asking price for the bits of muck they spotted when buying the lens, if the issue is more obvious it may make the price less than half that of a pristine copy.
    I've tried some VERY dirty lenses, and can still get reasonable images with them provided I keep strong light off the elements & boost the contrast. Muck at the front of the lens will encourage flare & anywhere within the lens it will reduce contrast.

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