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03-30-2014, 05:12 AM   #1
cyberjunkie's Avatar

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Tamron Adaptall-2 K/A lens not working with K-5 II

I have an old Tamron 90mm f/2.5 Macro, manual focus (the second version, with knurled focus ring).
The lens came with an Adaptall-2 ring, with electric contacts (K/A).
When i bought the lens, the Adaptall ring was not properly mounted. I took it out, remounted the ring properly, and found that the diaphragm lever was not moving freely, causing exposure problems.
I slightly bent the lever, and since then the lens worked well (i had to re-do a bit of bending one more time, cause the lever got somewhat stiff, probably for lack of use).

I am on vacation now, with my new (second-hand) K-5 II, and my trusty K200D as second/spare body.
Before leaving i didn't test the Tamron with the K-5, it was working with other cameras, so why it should not work with a newer, and better camera? :-)
Unfortunately today i discovered that my assumption proved not true.
I just tried with both cameras, many times, after removing and re-mounting the ring countless times:
the lens works perfectly with the K200D, and does not work at all with the K-5 II !!
It is immediately evident, the image in the viewfinder is dark, cause the iris is closed (if set to A), or at the set aperture (if not set to A).
The iris should open completely, once the lens is mounted, and should close to the working aperture just an instant before the picture is taken. That's what happens with the K200D.
I must say that there is something a little strange with this lens: if i remove it from the body, the diaphragm lever moves smoothly if pushed with a finger, but if i move the diaphragm ring away from "A", and close the iris step by step from f/2.5 to f/22, you can see the diaphragm blades closing... until it reaches midway between f/8 and f/11. Stopping down further, the blades close only after a slight "tapping" on the side of the lens body.
I can't check what happens if the ring is set to Auto ("A"), but i found that all the pictures i took with the K200D seem to be spot on, even dialing f/16 or f/22 using the thumb wheel.

I tried to describe the problem as well as i could, i hope it came clear.
It is obvious that there is a movement which is not totally free, in the adapter ring... but i can't understand why on earth the K200D takes perfect pictures (with the diaphragm ring set to A), while the new K-5 II can't even keep the iris open!
I tried with different exposition modes, i tried to operate the DoF preview, but to no avail.
It's weird that with the K200D everything is perfectly OK, i tried many times and all the pictures came perfectly exposed.
Any clue?



Last edited by cyberjunkie; 03-30-2014 at 05:20 AM.
03-30-2014, 06:33 AM   #2
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The Tamron Adaptall2 PK/a adapter is finicky. The contacts may align right and work well on on one camera mount but not on another. Did you try slightly moving the adapter mount to the left or right to see if it would make better contact on your K5 ll ? I got tired of screwing around with that adapter and only will use the adaptall2 PK manual ones now.
03-30-2014, 10:28 AM   #3
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I had a similar problem with a 01B 24mm. When I took the mount off the lens to investigate the problem it was clear that a small wheel (that is pushed on by a small plate on the mount to operate the auto aperture) was bent slightly out of true. Gently bending this wheel (ie its little mounting bracket) back into position solved the issue.

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