Help Needed: Tamron Adaptall Aperture Mechanism

[ballgofar]

I just purchased a Tamron Adaptall 300mm f/2.8 (model 60b) off of eBay along with its coupled 140F teleconverter. It came with a Nikon and a Minolta adapter, so I got from B&H a PK adapter. While I wait for the Pentax 1.7x AF teleconverter to arrive from China, I've been practicing manually focusing with this monster of a lens. I'll be bringing this on my Earthwatch Expedition to Kenya, so I want to be able to take full advantage of the photographic opportunities I'll have there. (Here's the link to the Earthwatch page if you're curious: Earthwatch: Lions Of Tsavo - Earthwatch)

I have encountered a problem, though. When then lens is not attached to the camera, I can rotate the aperture ring to manually change the aperture. And since I do not have the PKA adapter, this is how I'll have to adjust the aperture settings (right?). The problem is, when I put it on the camera (a K10d), this does nothing. Now I have (some) experience with manual lenses, so I know that the change in aperture does not happen until you press the shutter button or use the DOF preview thing. But still, no matter at what aperture I put the lens, it remains at f/2.8 when I take the picture. This is the case with or without the teleconverter. I tried another manual lens just now to see if the issue is with the lens and not the camera and, sure enough, the lens stopped down correctly.

Now this a huge issue because I'll likely be using one or both of the teleconverters most of the time, but I still want to be able to stop down if I have sufficient light. Any recommendations or advice would be tremendously helpful; I really want to get this to work. If supplying pictures or anything else would aid in this situation, I'd be happy to try to accommodate those.

[Blue]

Check your cameras operating manual and treat the adaptall P/K mount like an M lens.

[ballgofar]

Wow. I feel like I just wasted a lot of time. I fiddled around with the PK adapter (read: took it off and put it back on again) and stuck the lens back on the camera. And, would you believe it, it worked. I can change aperture, I can use the DOF preview button, everything! Changing the aperture actually changes the exposure now. Yippee!

And I spent all this time writing this whole thing for nothing....

But my lens works! . I must have put that adapter on wrong in the first place.

[Blue]

The adaptall mounts take a little practice to get used to. Once you have figured it out though, it is no problem in the future.