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07-19-2022, 10:54 AM   #1
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weird behavior between my KP and Tamron 10-24mm at 10mm - high shutter speeds

Apologies as I'm not sure if I should post this question/problem in the SLR lens discussion forum or in the KP-specific forum. So in a fit of LBA and nostalgia, I saw a good deal on a factory refurbished Tamron 10-24mm that I jumped on. I owned this lens a few years ago and generally enjoyed using it, but sold it when I needed to raise some funds. Later on, I got a Sigma 10-20mm f/4-5.6 that seems to offer better sharpness and more solid build quality than the Tamron. But there are times when I missed the slight extra reach to 24mm while using the wide angle zoom, so I thought I could get another Tamron 10-24mm to see if that copy's sharpness was better (and I could directly compare it with my Sigma 10-20 and keep the one that was best).

Here's where things get weird -- when mounted on my KP, the refurbished Tamron 10-24mm exhibits weird behavior -- set to 10-11mm, using Auto or Program mode, the shutter speed defaults to 1500 or 1000 (testing it indoors). As soon as I zoomed in to 12mm or farther, the shutter speed drops down to 45 or 30, etc.

I tried the lens on my Pentax K-5IIS and K-01 bodies and this doesn't happen. And my Sigma 10-20mm set to 10-11mm doesn't reproduce this problem on my KP under the same conditions above (using Auto or P mode).

What's going on here? Seems to be some weird glitch/electronic communication problem between my specific KP body and this Tamron 10-24mm lens. I even updated the firmware of my KP from 1.10 to 1.31 (been needing to that for a while anyway), but the problem still happens.

Anyway, I'm sending the Tamron 10-24 back to the seller for a free refund and free return shipping too. For the record, in my quick tests using simple snap shots around my house, the Tamron was no sharper than my previous copy at its widest apertures -- that is, needed to stop down to f/8 or so to improve the sharpness, which I think is common for this lens. And I think the Tamron is a lot more plasticky build than I remember, worse than my Sigma 10-20mm and Tamron 17-50mm. Finally the AF sounds louder and is slower than my Sigma 10-20mm f/4-5.6. So, even though the Sigma has a shorter zoom range and lacks the extra reach to 24mm that I had wanted, I'm keeping my Sigma!

Any thoughts on what happened? Does this occur with other lenses -- is it a third party lens issue? I don't think I've encountered this before using any of my lenses, native or third party.

Thanks!!


Last edited by seventysixersfan; 07-19-2022 at 11:11 AM.
07-19-2022, 04:20 PM - 2 Likes   #2
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Several years ago I bought a new Tamron 70-200 2.8. It did not work correctly on my K-30, I sent it back, they made some adjustments and returned it to me, it was still not right. I contacted them again and they said they only had one older Pentax camera to test with, and it had worked with that, and so they asked if I could send the camera back with it, which I did. When it came back to me it worked perfectly. I assume the mount on the lens and camera were not quite lined up, but that both were in the manufacturer's tolerance, but at opposite ends of the range, and since Tamron is reverse engineered it could be off slightly more. I'm pretty sure they made a slight adjustment to the mount. One nice thing is that Tamron was very quick with repairs and shipping.
07-19-2022, 05:36 PM   #3
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QuoteOriginally posted by ramseybuckeye Quote
Several years ago I bought a new Tamron 70-200 2.8. It did not work correctly on my K-30, I sent it back, they made some adjustments and returned it to me, it was still not right. I contacted them again and they said they only had one older Pentax camera to test with, and it had worked with that, and so they asked if I could send the camera back with it, which I did. When it came back to me it worked perfectly. I assume the mount on the lens and camera were not quite lined up, but that both were in the manufacturer's tolerance, but at opposite ends of the range, and since Tamron is reverse engineered it could be off slightly more. I'm pretty sure they made a slight adjustment to the mount. One nice thing is that Tamron was very quick with repairs and shipping.
Thanks! That is a helpful anecdote, and confirms my suspicion that this glitch probably doesn't happen with native Pentax lenses. (I remember having a weird aperture problem when using the Sigma 24mm f/2.8 super-wide II with my K-01, that didn't happen on my other K-mount bodies at the time).

Anyway, I could keep the Tamron and just use it with my K-5 IIS and K-01 but as I said above, I don't think it's as good a lens as my Sigma 10-20mm, so I'm sending it back. (And if I really loved the lens, I guess I could do what you did and send it back to Tamron with my KP for calibration)
07-22-2022, 04:11 PM - 1 Like   #4
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If it were me, I'd just send the lens back for a refund. Not performing as well as the Sigma 10-20mm would make it not worth the trouble. I know what you're saying about having the 24mm range. I have the very fine Sigma 10-20mm f/3.5, but also my long-time Pentax DA 12-24mm f/4 as well. I still sometimes enjoy the older Pentax lens, but find I use the Sigma lens more often. It provides the widest imaging of all my WA lenses, and with excellent quality. And this being an ultra-wide angle lens is what it is all about, yet with the versatile framing only a zoom lens can bring. This Sigma is also well-designed, with silent AF and a handy AF/MF switch in a well-built body. I have had no problem with either of these two lenses on my KP.

07-22-2022, 08:18 PM   #5
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QuoteOriginally posted by mikesbike Quote
If it were me, I'd just send the lens back for a refund. Not performing as well as the Sigma 10-20mm would make it not worth the trouble. I know what you're saying about having the 24mm range. I have the very fine Sigma 10-20mm f/3.5, but also my long-time Pentax DA 12-24mm f/4 as well. I still sometimes enjoy the older Pentax lens, but find I use the Sigma lens more often. It provides the widest imaging of all my WA lenses, and with excellent quality. And this being an ultra-wide angle lens is what it is all about, yet with the versatile framing only a zoom lens can bring. This Sigma is also well-designed, with silent AF and a handy AF/MF switch in a well-built body. I have had no problem with either of these two lenses on my KP.
Thanks -- lens is already back to seller and I got my refund. Have always had my eye on the DA 12-24mm and maybe I might try to get it someday -- I do enjoy the 10-11mm wide angle range though.
08-12-2022, 12:07 PM - 1 Like   #6
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QuoteOriginally posted by seventysixersfan Quote
(I remember having a weird aperture problem when using the Sigma 24mm f/2.8 super-wide II with my K-01, that didn't happen on my other K-mount bodies at the time).
I've had plenty of sigma lenses refuse to work on my K-01 full stop. It's very strange.
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