It's not always dust either, a lot of the times it can be small chips of
the black matte paint that have started to peel from the inside of the
lens. On zoom lenses it is impossible to seal the unit anyway, because of
lens elements moving around would cause a vacuum, or areas of high pressure
- so every time you zoom it sucks air in and out.
I wouldn't worry about it - you need a lot of dust to affect the pictures
in any noticable way. There isn't much to prevent this. I guess you could
go over your lenses with a small screw driver and make sure everything is
nice and tight. A protective filter might help keep dust from getting in
from the front of the lens.
You can get them cleaned at a repair place, but sometimes they do come back
with more dust from disassembling and reassembling the lens.
BTW, computers attract dust like crazy because most of them have fans to
constantly pull air through them, plus the electrics themselves attract
dust when they are powered on.
Todd
At 09:31 AM 8/7/01 -0400, you wrote:
>I'm lost...
>
>In the past few days folks have bought or are trying to sell "really
>great" lenses...... EXCEPT they have some dust & dirt inside them.
>
>I can understand the outside being FUBAR..... but how in the world does
>one get crud INSIDE of (what I thought was) a sealed unit??
>
>Everyone's reading the list on a computer. I'm sure everyone has been
>taught or has heard of how BIG dust & dirt molecules/particles are.
>Lenses are assembled, so some parts simply are "mating surfaces" with
>slip fits..... yet the machinist in me says that a slip fit can be as
>small a difference as .0005" and still work.
>
>Is this something I need to be worried about?
>How can ya prevent this from happening?
>How do ya "fix" it once it happens (or is that why this stuff is for
>sale)?
>
>This may be a old thread that's been thoroughly trashed... my apologies
>in advance.
>
>Scoot
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