Pentax 67 lens question

[Paddy C]

I'm waiting on the delivery of a 67 body and finder from Japan. In the mean time I went ahead and bought a 105 f2.8 from KEH. As usual it is in incredible condition but...

I was inspecting and testing the lens when I noticed the aperture blades do no move. They aren't even visible. I see there is something in the manual I downloaded about an automatic diaphragm. So is what I'm seeing normal operation?

Does the lens have to be mounted before the diaphragm starts opening and closing?

Feeling a bit daft, am I totally missing something here?

 

[Armoured]

Caveat: I'm answering this question without knowing the system that well, or having one to check. But on many lenses/mounts there is a pin that the camera system moves to stop down (close the aperture). Depending on which way it's spring loaded, the unmounted lens may not stop down. From this picture below of a 67 lens, there is a pin at the back as well as a tab on the side. It's probably one or both of these that need to be moved - you can try it yourself, carefully. (And of course, my caveat above should be enough to tell you that I'm making an educated guess and if one of them turns out to be the self-destruct pin, I'm not responsible).

 

[jan normandale]

here's where I'd post this question.... http://www.flickr.com/groups/67/

 

[Benjamin Marks]

That rocker/slider tab in the photo above can be set to manual or automatic. If the lens is off the camera, slide/set it to manual. Then stop the lens down. The Pentax M42 lenses in 35mm were built the same way -- used like a DOF preview lever and dead convenient when using stop down metering on a digi-body.

Ben Marks

 

[DaveW]

On the version I have (the s-m-c tak) you push the switch forward to reveal the "manual' label and you also pull up on the switch to keep it in that position.

 

[Paddy C]

Thanks guys.

I PMed Doug and asked him and he clarified things for me.

I think I'm one of the few people that always reads the manual and doesn't like to tinker with anything until I know everything about it.

The weird thing is that I spent some time searching and downloading manuals but couldn't find any info on it. The manual gives no explicit instruction on this feature of the lenses.