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.