I guess that that is a big plus point for two-touch zooms; no pumping!
Sincerely,
Roger Key
Good point. The zooming action has the inside of the lens acting almost
like a bellows, pumping air in and out.
_________________________________
John Hermanson www.zuiko.com
Camtech, Olympus Sales & Service since 1977
21 South Lane, Huntington NY 11743-4714
631-424-2121 For Free Olympus manuals,
please call 1-800-221-3000
_________________________________
----- Original Message -----
From: "Brian Swale" <bj@xxxxxxxxxxxxxxx>
To: <jochen.schiffler@xxxxxxxxxxx>; <olympus@xxxxxxxxxxxxxxx>
Sent: Thursday, June 13, 2002 9:44 PM
Subject: [OM] ( OM ) Dust in lenses
> 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
>
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