It does sound like it could be that then. Do they generally become
completely stuck with no warning, or would you expect to observe a
progressive decline?
Tom
On 28/02/07, Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
> The fact that it moves freely and feels right doesn't matter. On an OM
> mount lens there is no physical link between aperture lever and
> diaphragm except for pushing the aperture back open. On stop down the
> lever just gets out of the way to allow the blades to close and a very
> weak little spring pulls the blades closed.
>
> When you activate the stop down lever you're still feeling normal spring
> tension for the stop down lever itself... whether the diaphragm follows
> along behind or not.
>
> The simplest analogy I can draw is of a pinball machine with it spring
> loaded ball release and the ball. In the analogy the spring loaded ball
> release is the stop down lever inside the lens. The ball is the
> diaphragm and gravity in combination with the slope of the table is the
> lightweight diaphragm spring. When you pull back the ball release you
> expect the ball to follow along behind due to gravity. If it doesn't
> maybe there's some sticky substance under the ball preventing free
> movement. That's oil on the blades.
>
> Chuck Norcutt
>
>
> Tom Fenwick wrote:
> > I don't think that's what it is - everything moves freely, the spring
> > tension feels right etc, but the iris just doesn't stop down! It was
> > working fine last time I tried it, about a month ago...
> >
> > Tom
> >
> > On 28/02/07, Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
> >> What's the probability that this thing has oil on the blades and is
> >> stuck wide open?
> >>
> >> Chuck Norcutt
> >>
> >> Tom Fenwick wrote:
> >>> Hi,
> >>>
> >>> I've got a 24/2.8 which has stopped stopping down.
> >>>
> >>> I've removed the easy part of the back of the mount, and everything in
> >>> that section is working ok; ie the lever on the main part of the lens
> >>> is being operated but it's not doing anything.
> >>>
> >>> I guess something has come unhooked.
> >>>
> >>> Is it likely to be something I can get at and re-hook fairly easily?
> >>>
> >>> Thanks,
> >>>
> >>> Tom
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