Dust (in reasonable quantities) matters only when you are provoking flare.
Oil-free in general means diaphragm blades since they are usually the most
affected internal component. Some lenses have a tendency to get oil on an
element, where it can be quite destructive. My search for a 65-200 with
perfectly clear glass continues....
Julian
----- Original Message -----
From: "robert smith" <robnruth@xxxxxxxxxxxxxxxxxxxxxx>
To: <olympus@xxxxxxxxxx>
Sent: Wednesday, January 19, 2005 10:53 PM
Subject: [OM] Re: Oil Free?
>
> The good lens is now back together minus the oil.
> I only opened it as far as the levers in the back where the mechanicals
> are
> still a reasonable size.
> It now shuts right down with the preview button and is lovely and free to
> spring open again.
>
>
> The other lens with the sticking iris has taken loads of fantastic
> pictures
> in the past even though there are some sizeable dust particals inside.
> Does
> this not matter?
>
> Rob
>
>
> ----- Original Message -----
> From: "Moose" <olymoose@xxxxxxxxxxxxxxx>
> To: <olympus@xxxxxxxxxx>
> Sent: Wednesday, January 19, 2005 9:01 PM
> Subject: [OM] Re: Oil Free?
>
>
>> 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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