At 10:25 PM 01/11/2001 -0800, you wrote:
So how do dust get into the (older) lens? I can see fungus growing
due to moisture content, but dust? Or may be they are paint and
whatnot from the interior of the lens?
Lenses are open tubes, generally (this allows them to change their
length in focusing operations). As you move the tube back and forth
during focusing, air gets sucked in or blown out, and with it, dust.
The only exception to this are "internal focusing" lenses, which
still have moving tubes, but are enclosed in an outer tube of fixed
length (so it can be 'completely' sealed). Even with sealed tubes,
there are still mechanical linkages which allow small quantities of
dust in over long periods of time.
The dust is generally harmless, although large quantities of it can
lower contrast significantly. The dust particles do not resolve in
the image.
Garth
Presumably one could build sealed lenses with inert gas
pressurization like binoculars from Leica or Zeiss, at similar cost.
--
Winsor Crosby
Long Beach, California
< 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 >
|