How does dirt get into a lens?

6 days 14 hours ago #639828 by Hawkins
I have a couple of older lenses that have dirt inside of the lenses.  How is that even possible, I thought these things are sealed up?


How would you even get that out?


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6 days 14 hours ago #639829 by Nikon Shooter
This will happen sooner or later to non IF lenses
— older ones even more so. The only solution is
the workbench of a good specialised technician.

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6 days 14 hours ago #639834 by Hawkins
But why is this happening, are the seals bad?  


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6 days 14 hours ago #639835 by Nikon Shooter
Not really. IF lenses had the same seals then but the non IF
lenses are pumping dirt in both when focusing and zooming.

Of course, with time, seals wear out too and may be replaced.

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6 days 13 hours ago #639861 by Hawkins

Nikon Shooter wrote: Not really. IF lenses had the same seals then but the non IF
lenses are pumping dirt in both when focusing and zooming.

Of course, with time, seals wear out too and may be replaced.



Thank you for your help.  I don't mean to be asking so many questions, but I don't understand when you say "pumping dirt in both when focusing and zooming".  How is that even possible?  


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6 days 13 hours ago #639865 by Nikon Shooter
In IF lenses (for internal focussing), any lens movement is
done internally — no apparent change in the morphology of
of the lens — so no exchange with the outside world in terms
of dust and humidity.

Non IF lenses do expand and contract when operated and
that means air — including dust and humidity — exchanges.
Consequently, they are also more prone to fungus growth.



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6 days 6 hours ago #639918 by Ozzie_Traveller
G'day Hawkins

As any zoom lens extends and contracts - called the 'trombone' effect, air must be sucked in and pushed out of the lens barrel as it is not a vacuum. This suck & blow is where the dust ingress comes from

Hope this helps
Phil from the great land Downunder
www.flickr.com/photos/ozzie_traveller/sets/


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4 days 6 hours ago #640241 by Neil Dulay
So, I'm going to jump in here.  How would you even get that out then?  


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4 days 6 hours ago #640243 by Nikon Shooter

Neil Dulay wrote: So, I'm going to jump in here.  How would you even get that out then?  


The answer is…

Nikon Shooter wrote: The only solution is the workbench of a good specialised technician.


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