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[OM] Re: Oil Free?

Subject: [OM] Re: Oil Free?
From: Moose <olymoose@xxxxxxxxxxxxxxx>
Date: Wed, 19 Jan 2005 13:01:14 -0800
robert smith wrote:

>My question is:
>When people say that a lens is oil free are they just refering to the iris 
>area?
>
Probably, as that is all one can see without opening the lens up as you 
have done. However, there should be no oil anywhere at all in the lens. 
What happens with age, probably dependent on the ambient temperature 
over that age and perhaps the particular batch of grease used, is that 
the grease in the may helicoid break down, releasing a lower viscosity 
fraction - oil. This then may migrate to the diaphram mechanism and/or 
the levers in the back. This problem is MUCH more prevelent in the 
design labeled 'MC', although I've seen it in 1 miJ lens with an 
earlyish serial number for that design. Whether the lach of a problem in 
later serial # miJs is a real improvement or just that they are younger 
I don't know. Uncommon in older F.ZUIKOs, whether due to better grease 
or the different mechanical design. Unfortunately, they aren't optically 
as good.

>My good lens has light oil around the flat disc like levers at the back of the 
>lens but none further in, just white grease on the scrolls at the side.
>Should I remove the oil from the disc like levers before I reasemble the lens 
>to leave it all dry?
>
Yes, it should be dry there. In fact, that may be the whole problem. Oil 
on those large flat surfaces adds a lot of friction to the DOF setup.

Moose



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