Olympus-OM
[Top] [All Lists]

RE: [OM] Best way to see dust in a lens?

Subject: RE: [OM] Best way to see dust in a lens?
From: "Daniel" <danrich@xxxxxxxxxxxxx>
Date: Fri, 1 Aug 2003 17:53:10 -1000
Much Mahalo's from Maui
Daniel


-----Original Message-----
From: owner-olympus@xxxxxxxxxxxxxxx
[mailto:owner-olympus@xxxxxxxxxxxxxxx] On Behalf Of Moose
Sent: Friday, August 01, 2003 11:09 AM
To: olympus@xxxxxxxxxxxxxxx
Subject: Re: [OM] Best way to see dust in a lens?

All normal design lenses cycle air in and out as they are focused. As 
the focusing mechanism moves the main body of the lens forward to focus 
closer, air is pulled in from the back. Focus back to infinity and air 
is pushed out again. The whole thing gets more complex with zooms. 
Internal focus lenses likely move less air in and out from outside 
except when they are zooms that change length with fl, in which case 
something has to fill the expanded internal space. Macros are perhaps 
more vulnerable than regular primes due to the greater focusing 
extention moving more air, but less so than many zoom designs.

In any case, the modest amount of dust found in most used lenses makes 
absolutely no optical difference. Look at it this way. If dust were a 
real problem, top end 'pro' lenses would incorporate filters (like hard 
drives, where it makes a big difference), but they don't and never have.

Get a fine layer of reflective white dust in a lens and it will lose 
contrast, but the few bits of darkish dust in most lenses just don't
matter.

Moose

Daniel wrote:

>I didn't know about the macro pulling in dust Thanks for the info 
>



< 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 >


< 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 >


<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz