How does the OM-Mount work?

[CameraRick]

Hi there,

maybe a strange question.
I just got two new Lenses, both RMC Tokina 28mm; the first is for the OM-Mount, the second P/K (Pentax K I think).
The Pentax K doesn't got all of it's screws, so I can't use it at the moment.

But the OM will do - I think, at least!
When I pull the Iris-Ring to stop down, it simply doesn't change. The blades tand still, nothing happens.
Is this normal, or kinda broken? I remind the lenses from the FD-Mount, which were only pullable when attached - at the moment I don't have an Adapter to test it on my EOS.

Regards,
Lucas

[hinnerker]

There are two sliders/lever at 9'0 Clock on the rear side of the lens.. push one of them and close aperture, thats the same as the adapter does.. should work. If not, blades are stuck.


in Deutsch: OM hat zwei Übertragungshebel von denen einer bei Einschrauben in die Kamera oder den Adapter dafür sorgt, das die Blendenwerteinstellung übertragen wird und der andere muss eingedrückt/eingedreht sein, damit die Blende sich verstellen läßt. Der Hebel befindet sich von hinten auf die Linse geschaut etwa in 9 Uhr stellung.

Cheers
Henry

[symphonic]

I was puzzled by it too when I got my only OM lens. Here's some pics to show what Henry said, sorry for crappy quiality, it's quite dark in my room.

Here is the lens with an OM-to-EOS adapter on. You can see that the adapter has a little screw which hold the lever in position so that aperture is changed freely:


Without the adapter. The two silver buttons are used to release the lens from a camera (or adapter).

[calvin83]

[WolverineX]

[CameraRick]

Hi there,

thanks for this assistance
I opened the Lens, made some adjustments and now - it works

Now I opened the Pentax K Lens, and I had to clean it down to the blades (I hate to clean and reassamble the Iris ). Now it works just fine I think (it stucked due to heavy use of oil and stuff), but I have problems to get it to actual work on a Camera - at least I think this, as usual I don't have an Adapter or a Camera

On this lens, there's one crank on the backside, which is attached to a spring inside. When it's attached, is this crank pulled fully against the spring, or something like that?

Regards,
Lucas