[pentax_wayne]

I just purchased a tamron 400/f4 lens. I took some test shots on a Canon 50D coupled with a canon 1.4X TC and it seems likes a great lens.

Now I'm having trouble attaching it to a pentax k10D.

First I open the lens aperture to f4 and then I put on the 1.4X TC. Everything seems fine, nothing spins. Then I put on the tamron adaptall PKA adapter, clicks into place, again everything seems fine.

Then I attach the pentax K10D. I push a little black button on the PKA adapter and this allows the lens aperture to be set to the AE position. And now the whole thing spins about the lens axis and I know this can't be right...if i spin it enough the combo of the TC, pka adapter, and k10D comes off the lens.

I must be doing something wrong, can anybody offer suggestiions. I have the instruction manual for the pka adapter, but i can't find anything online for the adaptall 1.40X TC.

sorry if this has been covered before... this is my first post. Thanks.

[bobpur]

You are probably pressing the little silver lens release arm by accident when turning the aperture ring to Ae.
Assemble the whole thing and put it in Auto before installing it.

[pentax_wayne]

thanks. I tried that and various other combos and no matter what the TC+pka adapter+k10D spins about the lens axis til it comes off.

I'm pretty sure the pka adapter is in good shape as I've used it with a tamron 200-500 f5.6 zoom. The TC i just ordered from KEH this week.

On EOS 50D set-up, i have the tamron 400 /f4 + generic adaptall to EOS adapter. the generic adapter clicks right onto the canon 1.4 TC, and everything seems to work in stop-down metering mode.

If I try tamron 400/f4+tamron 1.4X + generic adaptall to EOS adapter and try to mount to the camera i get the same problem..the whole setup spins about hte axis of the lens.

Arrrrrgh... i imagine i must be doing something really dumb.

[littledrawe]

There are two tabs on the mount that slide into the cutouts on the lens and those have to be lined up for it to work properly. It sounds like you know what you are doing so this is just a suggestion but there would be two sets of these, I think, one on the 140f and one on the mount so if those aren't lined up it might not work right.