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12-09-2009, 10:43 AM   #1
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[langtitle=it]Tamron trouble[/langtitle]

Hi to everybody,

my first attempt to mount a non-Pentax lens on my K20d give me a problem:
my Tamron SP 90/2.5 gives me a maximum aperture of F3.5 only instead of F2.5 as it should, in addition, into the camera menu, there is no 90mm focal length (only 85 and 100), so the lens is not recognized and no stabilized (?).
Any of you had the same problem?

Thanks for replay

12-09-2009, 11:24 AM   #2
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I have the same lens as you. Just put 85 into the SR. It will stablize fine.
Do you have a PK or PKA adapter on the lens?
12-09-2009, 11:58 AM   #3
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QuoteOriginally posted by VincenTC Quote
Hi to everybody,

my first attempt to mount a non-Pentax lens on my K20d give me a problem:
my Tamron SP 90/2.5 gives me a maximum aperture of F3.5 only instead of F2.5 as it should, in addition, into the camera menu, there is no 90mm focal length (only 85 and 100), so the lens is not recognized and no stabilized (?).
Any of you had the same problem?

Thanks for replay
ClassA wrote an article about the Adaptall-2 P/KA adapter issue you refer to - there is an easy fix. Click HERE to go straight to the article, or look under the Articles brick above, in the Lens Articles section.

FWIW, after I did the fix my 90/2.5 w/ P/KA adapter works perfectly (as do kmy other three Adaptall-2 lenses).
12-09-2009, 11:59 AM   #4
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QuoteOriginally posted by wildlifephotog Quote
I have the same lens as you. Just put 85 into the SR. It will stablize fine.
Do you have a PK or PKA adapter on the lens?
Hi, thanks for replay.
Mine is the PKA adapter: have You the same problem with the maximum aperture?

12-09-2009, 11:59 AM   #5
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QuoteOriginally posted by VincenTC Quote
Hi to everybody,

my first attempt to mount a non-Pentax lens on my K20d give me a problem:
my Tamron SP 90/2.5 gives me a maximum aperture of F3.5 only instead of F2.5 as it should, in addition, into the camera menu, there is no 90mm focal length (only 85 and 100), so the lens is not recognized and no stabilized (?).
Any of you had the same problem?

Thanks for replay
Vincent, try to demount and mount the lens again. Sometimes it happen when I attached old manual lens on my K20D too. Very seldom but it happened.
Or maybe you can try to clean the electric contacts on the lens and the camera as well when you demount it.

About choosing the focal length manually for SR, like what wildlifephotog already said, choose the one closest to your lens focal length even if it means a little bit smaller or bigger. The SR will work with any lens as long as it has Pentax K-mount.
12-09-2009, 12:06 PM   #6
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QuoteOriginally posted by HermanLee Quote
Vincent, try to demount and mount the lens again. Sometimes it happen when I attached old manual lens on my K20D too. Very seldom but it happened.
Or maybe you can try to clean the electric contacts on the lens and the camera as well when you demount it.

About choosing the focal length manually for SR, like what wildlifephotog already said, choose the one closest to your lens focal length even if it means a little bit smaller or bigger. The SR will work with any lens as long as it has Pentax K-mount.
And now my Tamron goes! Thanks to everybody!
12-09-2009, 12:21 PM   #7
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I did at first. But then I cleaned the screw tips off. Now it goes to 2.5 in AV and P mode.
12-10-2009, 03:48 AM   #8
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Hi my friends,
my Tamron goes but only at F3.5, still.
Please, what is the screw that I must clean? Is it that of the three red circled taller on image in the post of Class A? Sorry, I don't understand...
Thanks.

12-10-2009, 05:33 AM   #9
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Go to this thread, https://www.pentaxforums.com/forums/pentax-lens-articles/50689-fixing-tamron-...a-adapter.html

Scroll to first photo. Clean the red circled screw tip shown in the right hand red circle.
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