Your lens is perfectly normal. OM lenses are normally fully open.
Other cameras may have their lenses normally closed. When you turn the
aperture ring on an OM lens all it does is move an internal cam that
sets a stop point. There is no physical connection between aperture
ring and aperture leaves. Actually closing the aperture down is the job
of the camera body. The camera body presses on the len's activation
lever which allows (not forces) the blades to close down to the stop
point set by the aperture ring. The DOF preview button also acts the
same way. Depressing it allows the blades to close down.
Hold the DOF button down while you turn the aperture ring and you'll see
the blades move with the ring.
Chuck Norcutt
Matthew Granger wrote:
> *Hi All*
>
> * *
>
> *Here's a tricky question. I have an old OM lens – Sigma Pantel
> 1:2.8f=135mmMade in Japan. On the aperture dial it has from
> 2.8-22m then PAN 64 in red writing. *
>
> *I have this connected to my E500 via an adapter, however it seems the
> aperture control is not working – seems to be set wide open. Changing from
> 22 to 2.8 makes no difference to the actual exposure. *
>
> *Looking at the lens off the body, turning the aperture dial does not seem
> to be physically attached to blades at all. It is however moving a small
> metal arm on the inside of the mounts.*
>
> * *
>
> *Anyone know whether the lens is faulty, or what I am looking at?*
>
> *Matt *
>
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