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Re: [OM] Re: Metal surfaces and polarizers

Subject: Re: [OM] Re: Metal surfaces and polarizers
From: "John A. Lind" <jlind@xxxxxxxxxxx>
Date: Tue, 30 May 2000 23:07:33 +0000
Yes, brass is a nice material for this task.  I cannot speak about the
material on the current 50/1.8 MC, but if it is like all the other Zuiko
lenses I have (and had) I believe it's anodized alumin[i]um (that's what it
behaves like).  The ring inside that may be a type of plastic (acrylic??
polycarbonate??), but I'm certain the threads are metal.

Alumin[i]um rubbing on alumin[i]um under pressure without any lubrication
"galls" easily (transfers minute amounts from one surface to the other).
Even if it doesn't visibly gall, it sticks as if it has been fused
together.  OTOH brass seems to be almost self-lubricating, at least under
friction that doesn't generate too much heat, such as filters screwed
together tightly.  When stacking filters with screw-on stack caps on each
end, I had occasional trouble trying to get the older alumin[i]um ringed
filters apart.  It was yet one more reason I started dumping them a while
ago for filters with brass rings (along with better optical quality).

-- John

At 16:43 5/30/00 , Tom wrote:
>Hi Frank,
>
>Apparently brass and aluminum (aluminium for you GBers) have very low 
>friction together. A match made in heaven!
>
>But aren't ALL lens threads steel?
>
>Tom
>
>At 2000 May 30 - Tuesday 20:39, Frank Ernens <olympus@xxxxxxxxxxxxxxx> 
>spoke about *Re: [OM] Re: Metal surfaces and pol...* saying
>
>> John Lind wrote:
>> 
>> > (5)  Precision and quality of the filter ring to get the filter
>> > optics perpendicular to the lens axis, keep it that way under
>> > repeated use, and not cause excessive wear to the lens ring.  IMO
>> > brass is best, aluminum runs second but can stick easily making
>> > removal difficult, and forget about plastic.
>> 
>> I agree, but could a brass filter damage a lens with plastic threads?
>> 
>>     Q1: Does the current model 50 f/1.8 really have plastic
>>     filter threads (shoddy), or is just the bezel plastic like
>>  that on my 24 f/2.8?
>
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