Tamron SP90/2.5 52B Help

[Tervueren]

Recently got hold of one complete with the 18F 1-1 adapter, it looks in excellent cosmetic and optical condition but I'm not familiar with it and not sure I'm using it correctly.
Problem 1, without the adapter I can focus throughout the full range but with the adapter I can only focus on objects very very close to the lens (inches).
Problem 2 if i select any aperture value smaller than wide open as soon as I get to approx 3ft focus distance the aperture snaps back to wide open and the only way to get it working again is to reselect 2.5 operate focus slightly (you hear a click) then I can select a different aperture once again but can only retain it above 3ft distance.
Is this a lens feature, am I having a blonde moment or is it sick.
Thanks
John

[visualopsins]

Problem 1 is a feature. The 1:1 adapter is only an extension tube; with extension tube lens focuses closer, not to infinity anymore.

Problem 2 may be the adaptall-2 adapter isn't seated properly/completely on the lens. Need to know camera mount to help more.

[Tervueren]

[visualopsins]

Without an adapter attached, the lens aperture should remain open when ring is turned.

The aperture is operated by pressing on the roller seen here:



Is something interfering there?

[Tervueren]

[visualopsins]

Focus on mine is quiet & smooth; no clicking/switching sound(s) as focus ring is turned...

[Tervueren]

Thanks for that, so it does look like there must be some interference at that point from the the focus mechanism with the aperture mechanism, I'll have to get a repair estimate to find out if it's worth the cost

[Smoli4]

well if you wanna try fix it yourself i can tell you whats the problem exactly.

you only need to unscrew the ring in the filter thread, then unscrew the grey element block.
when you will hold the element block in your hand you will see leaver witch moves the aperture is banded. straightened it with a pair of pliers and insert it back to place - make sure leaver you just fixed slides on the leaver witch moves the aperture inside lens itself.

that should do it.

[Tervueren]

Thank you Smoli, I think given the price of repair and the shipping costs involved versus the replacement lens cost then it makes more sense to give it a try and fix it myself. I'm off to local camera shop to get a rubber lol.
Thanks to both of you
John

[Tervueren]

Smoli, removed the retaining ring and now I'm looking at 4 screws which look like they are holding 2 metal plates in place, do I have to remove these and then does the block come out or is there something else in the mount area, you may have guessed by now that I've not done this before

[Tervueren]

Smoli you were right the little 2 prong fork on the block was bent, anyway replaced it exactly as removed but it was still the same, took it apart again and found this in the photos, the long bar with which the fork engages is around 1cm shorter than the one on the opposite side also when you turn focus the longer bar stays in situ the shorter bar drops down and must disengage from the fork, should they both stay in place meaning that it has somehow become detatched, why oh why did I think this was going to be easy lol.
Sorry for bad photos

[Tervueren]

OK, I presumed because that was the way I took it apart that it was in the correct position, with the block rotated 180 so the fork engages with the fixed bar it seems to work fine, anyway enough for tonight I'll give it a clean up in the morning and give the lens a whirl

[Smoli4]

hey sorry for my late answer.

you need to place the element block in the longer fork. the shorter fork comes from the mount area and, in turn it is what moves the longer fork and then the aperture leaver.

and if you will any problem i will unscrew my lens and post exact pictures of what going on there. as mine seems to work just fine

[Tervueren]

[Smoli4]

great im glad i could help!
and yeah apart from that front element group my lens was in pieces literally.. i reassembled it maybe 5-6 times until everything worked as it should