Hi Jochen,
Lenses are not sealed airtight. There's no practical way they can be.
Every time a lens is focussed to a different focal length (except for IF
lenses), the lens body increases or decreases in length. This means the
lens volume alters. Thus air moves in or out of the internal cavity as the air
pressures inside and outside the lens equalise..
If the outside air is dusty, dust enters the lens then settles on any surface
to
which it is attracted.
And there's your answer.
Brian
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|