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03-23-2023, 06:23 PM   #1
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Tamron SP 350 mount to a Pentax k-70

Greetings all. I'm a brand new user of this site. Looks informative. I've been a Pentax user all my life (which equates to over 40 years of using this brand.)

Question: frustrated that after buying a new Pentax k-70 body recently, I am not able to use the Tamron SP350 even though the lens attaches properly (Adaptall-2 mount). I've used it before with my old K-x (not able to use automatic features but still able to shoot). Can anyone tell me why it turns on and can focus but shutter won't work and the f-stop indicator on the camera screen keeps flashing?

Thanks for any advice.

Tim.

03-23-2023, 06:45 PM - 2 Likes   #2
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Did you enable the camera set to accept lenses with an aperture ring?
03-24-2023, 01:25 AM   #3
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QuoteOriginally posted by byerses Quote
Greetings all. I'm a brand new user of this site. Looks informative. I've been a Pentax user all my life (which equates to over 40 years of using this brand.)
Question: frustrated that after buying a new Pentax k-70 body recently, I am not able to use the Tamron SP350 even though the lens attaches properly (Adaptall-2 mount). I've used it before with my old K-x (not able to use automatic features but still able to shoot). Can anyone tell me why it turns on and can focus but shutter won't work and the f-stop indicator on the camera screen keeps flashing?
Thanks for any advice.
Tim.
Which mount do you have fitted to your lens?
You'll only get an aperture read-out with the PK/A mount (with the electrical contacts).
If you're using one of the earlier (or third party) mounts the K-70 will treat it as a totally manual lens and you'll need to do as ramseybuckeye suggested above, see p122 in the Operating Manual.

I think I'm right in assuming your lens is a mirror lens, in which case you don't "need" the (more expensive) PK/A adaptor, 'cos you don't need the aperture read-out on a fixed aperture lens
If so, just set the menu option as above and enjoy
03-24-2023, 11:33 AM   #4
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QuoteOriginally posted by kypfer Quote
I think I'm right in assuming your lens is a mirror lens, in which case you don't "need" the (more expensive) PK/A adaptor, 'cos you don't need the aperture read-out on a fixed aperture lens
If so, just set the menu option as above and enjoy
On my Tamron 55BB 500mm f8 mirror, the PK/A mount is slightly annoying because the camera now thinks it can set aperture to f2.8 or whatever. So it can lead you to think all the modes work but they kind of don't. You just have to know that and use Av or M.

03-24-2023, 01:35 PM   #5
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QuoteOriginally posted by Just1MoreDave Quote
On my Tamron 55BB 500mm f8 mirror, the PK/A mount is slightly annoying because the camera now thinks it can set aperture to f2.8 or whatever. So it can lead you to think all the modes work but they kind of don't. You just have to know that and use Av or M.
You can potentially modify the mount by using nail polish to blank out spots on the lens side of the mount to correct the F2.8 isssue.

I did this on my 200-500/5.6 because the natural maximum aperture reported by this lens even with the PKA mount is F4. You might not think this is an issue, but it is a disaster once you decide to use a flash
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