For changing lenses etc in unfavorable conditions such as wind-driven dust,
sand, etc just include clear "trash" bags in your kit. They don't weigh
anything or take up much space when kept in their "out of the box/off the
roll" flattened state folded up. Carry a few in case you lose one (or two!).
LEE
----Original Message Follows----
From: "Brian Swale" <bj@xxxxxxxxxxxxxxx>
Subject: [OM] ( OM ) Dust and other foreign bodies in lenses - follow-
Hi folk,
It's not just zoom lenses (push-pull zoom or not) that behave this way.
Many / most macro lenses have a lot of helicoid travel and therefore there
is
a lot of air displacement during use. Lenses that focus close may in some
instances have the same larger movements (eg 90, 100 f/2).
Operate your lenses in a quiet place and listen. Feel the resistance to the
focussing movement as it forces air past the seals and the mounting flange.
Also, some lenses have a yawning gulf at the back when opened up. I
noticed this first when swapping my Zuiko 100 f/2 for another when doing
closeup shots in the field among leaves, pine needles and what have you. I
noticed a little grass seed had flicked into the cavity and was (was!) stuck
on
the grease on the helicoid.
Just imagine what happens when you are changing lenses in a desert with
fine sand and there's a wind blowing (usual ?) Or a sandy beach. Or ... ...
almost any place. Or focussing a lens in a sandy desert - or construction
site etc etc.
The point Moose made to Jochen about the effect of the little hair on photo
quality is very valid. Imperfections, especially dark-coloured ones and near
the front, have little or no perceptible effect on the picture quality.
However, in my opinion, beware dirt etc on the rear element; and any kind of
light-coloured haze which will bounce light around, reducing contrast and
detail .
Brian
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