The very early sign would be a smear of oil where two aperture blades
overlap. This would be visible as a slightly darker area of the blade
surface underneath. Note that sometimes older lenses show wear at the
overlap point, but that looks more like a shiny/polished look at the overlap
part. The effect of oil is to increase the force needed to slide the blades
past each other, to the point that the little springs inside the lens that
are supposed to do this can't.
I've seen oil on apertures on rangefinder lenses, but it doesn't cause the
same problems as lense with 'auto aperture' mechanism. I suppose it could
cause problems on simple rangefinder cameras which stop the lens down as
part of an auto-exposure setting process, but more usually the oil problem
in those is with leaf shutter leafs getting sticky.
--
Jim Brokaw
OM-'s of all sorts, and no OM-oney...
on 7/10/03 4:47 PM, Andrew L Wendelborn at andrew@xxxxxxxxxxxxxxxxxx wrote:
>
>
> A question.
>
> I have seen several references to this oil problem, but I've never actually
> seen a lens with it (I think).
>
> AFAIK none of our lenses exhibit this phenomenon (even the older PEN D,
> Agfa Optima I, Voigtlander Perkeo E, Rolleicord etc).
>
> I've seen a picture of oil in a lens. Not nice.
>
>
> But I would be interested to know what are the EARLY signs of oil on aperture
> blades etc, just in case it ever happens to any we have, or as I guess is
> inevitable now, when the temptation to expand the collection arises ...
>
>
>
> thanks
> Andrew
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