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[OM] ( OM ) why keep a filter in front of your lens

Subject: [OM] ( OM ) why keep a filter in front of your lens
From: "Brian Swale" <bj@xxxxxxxxxxxxxxx>
Date: Fri, 15 Nov 2002 20:18:00 +1300
Hi folks,

An aside to the story of the 35-70 lens that just turned up here the other day, 
it had a Vivitar skylight filter on it.

Today as I was looking at the whole set-up more closely, I saw that the filter 
was rather grubby. So I got out the box of Olympus tissues, huffed on one 
side of the filter to moisten it, and tentatively rubbed the surface.

It was soon obvious that there was a thick layer of accumulated grease of  
years on that glass. So I put some dish-washing detergent in the sink, added 
some warm water, and immersed the filter. It had no perceptible effect on the 
grease. So I applied some undiluted detergent direct to the wet filter and 
rubbed it in gently with the pad of my fingertip. It seemed to make a kind of 
emulsion. After not more than about 10 seconds of this I rinsed the detergent 
off vigorously and then soaked again this time in fresh water, for about 10 
minutes, to try to remove all detergent from wherever it had penetrated. 

I was amazed to find that there was still a definite trace of grease. It took 
about  10 - 15 minutes of gentle work with huffing and lens tissues to remove 
all the smeary stuff.

I have no idea where that filter has been for the last 15 or so years. The lens 
looks hardly used..  If the filter and lens have been together all the life of 
the 
lens, I'd better pay some attention to the barrel exterior. But it is also 
quite 
possible the two have led unrelated lives.

But just imagine the state that the outer surface of the front lens element 
could be in had a filter not been on. And I would not use detergent on the 
lens. Quite possibly the filter has given major protection to that lens.

Brian

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