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08-28-2012, 05:54 AM   #1
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Unusual adaptall aperture issue

When using viewfinder stop-down preview I see an aperture issue that does not happen when using the green button (in modes where this stops down momentarily to meter).

With lens aperture set to AE:
1) Green button works flawlessly as expected:
- Aperture constricts and then re-opens to full dilation. Every time.
2) Stop-down preview fails ~50% of the time:
- First press will usually constrict, but often not to the correct aperture, and then re-open, but often not to fully open.
- Second press usually constricts, usually to the correct aperture, and then re-open, usually to fully open.


With lens aperture set to any manual aperture (not AE):
1) Green button works flawlessly as expected:
2) Stop-down preview works flawlessly as expected:


Has this problem been seen before?
Suggestions?

K-5 v1.13
Tamron Adaptall PK/A adapters (I have 2, they were obtained separately and yet both behave the same way)
lenses tested:
Tamron 300mm/2.8 (60B)
Tamron 70-210mm/3.5 (19AH)

Both adapters and the 60B's internal springs, moving parts, rollers and contacts look to be in excellent condition with no sticking or corrosion (I have had them disassembled, yes).
Most likely to happen with apertures between f/16 and f/6.3.
Yes, I understand how to use adaptall adapters and the in AE/manual aperture modes :)
No, this is not related to the "'F--' intermittently displayed due to non-conductive screw coating next to the contacts" issue.

08-28-2012, 07:07 AM   #2
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I would need to check this behavior. i have PKA adaptors on ny 28/2.5 and 200-500/5.6

it may simply be that there is too much play in the adaptors. Note that on my K5 and K7 I notice some lack of aperture indication as a function of play on the mounts but that should never impact fully open aperture only the stop down aperture.
08-30-2012, 11:45 PM   #3
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Original Poster
Did you get a chance to check yet?

Also; slight rotational play is an issue on my adapters, I think it's due to the latch and catch having a very small tolerance before movement occurs, and the angled design of the contact surfaces may gradually wear them. I'm planning to test this further and maybe add a sliver of solder to the catch and see if that tightens it a bit.
However when testing my original issue above i was making sure to not rotate the lens at all. So I doubt this was a factor.
08-31-2012, 04:14 AM   #4
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No. It will be on the weekend, with my 200-500/5.6

09-03-2012, 03:12 PM   #5
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Tried mine this weekend.

No issues at all. Adapter on 200-500/5.6 worked flawlessly
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