Hmmm.
In my experience the AF-C on Nikon remains quiet when I reactivate contionous AF no matter, what's happening or if the camera's mounted on tripod or not when I turn the aperture wheel. Also, when I stop AF and refocus again, I always hear a sound - and the focus scale / ring is moving a fraction. I must say, impressive you see that - if I recall correctly, the focus scale and ring is quite dense on the Tamron: 0.29____0.5___0.7__1.1_3 ∞ (had to look that up). Hard to see movement between 3 m and ∞.
Edit: As for selling your Pentax gear: It was an easy way to go for me, I never grew to the K-m and K-x. Cheap ffeling plastic stuff, I never looked back. With K-3 and K-5 I wouldn't feel so easy about, but at the other hand: Although I like some of the features of the new FF Pentax and would go for a new body with those appearing in a Nikon (the very special tilting LCD, U1...U5(!) and the wheel with some menu settings on top of it) I would not go back to Pentax anymore. Lenses are limited and I recall some manufacturers stopping to offer interesting lenses in K-mount.
Quote:Hmmm.
In my experience the AF-C on Nikon remains quiet when I reactivate contionous AF no matter, what's happening or if the camera's mounted on tripod or not when I turn the aperture wheel. Also, when I stop AF and refocus again, I always hear a sound - and the focus scale / ring is moving a fraction. I must say, impressive you see that - if I recall correctly, the focus scale and ring is quite dense on the Tamron: 0.29____0.5___0.7__1.1_3 ∞ (had to look that up). Hard to see movement between 3 m and ∞.
Edit: As for selling your Pentax gear: It was an easy way to go for me, I never grew to the K-m and K-x. Cheap ffeling plastic stuff, I never looked back. With K-3 and K-5 I wouldn't feel so easy about, but at the other hand: Although I like some of the features of the new FF Pentax and would go for a new body with those appearing in a Nikon (the very special tilting LCD, U1...U5(!) and the wheel with some menu settings on top of it) I would not go back to Pentax anymore. Lenses are limited and I recall some manufacturers stopping to offer interesting lenses in K-mount.
Don' forget the Tamron 17-50 is on the K3 here.......It is not necessary to read the scale to check the focus change, you can hear the screw-drive "gruck" and see a "slight" barrel movement we are talking 5cms front focus at 2.5 meters or so, just enough to ruin the shot!
Quote: I would suggest trying a series of test shots with a range of shutter speeds to try and find the speed where the problem is the most troublesome and avoid them, à là Nikon! If that doesn't resolve the situation you could either leave the VC off or return the lens to Tamron,
Your version was one their first ventures into stabilized lenses.
Hey all - many thanks for all the replies! This may be a more complex problem than anticipated, but Dave might be right - I'll run another series of test shots with a tripod and different shutter speeds to see if it makes any difference over the next weeks when I find some time. Will report back.
The lens itself already had an oddyssey: I've come to a point where it's "ok" for my personal amateur photo purposes for now. I bought the Tamron new in Germany in April '15, noticed a bad front focus straight away. Back to shop (Media Markt), and they let me try another sample on my EOS 1000D, same issue, but competent sales guy that knew about the issue for a change.
Back in Ireland (where I live), contact Tamrom UK Support (Intro 2020 Ltd.) and they honoured the warranty no problems. Sent lens & body in, came back the same way, same front focus. Sent in to Tamron a second time, then they updated the lens firmware again, and also adjusted the following (copy & paste from Tamron UK Support): "the infinity point was moved along with adjustments made to the resolution power.".
Now, with my basic optics & physics school days knowledge moving the infinity point somewhat makes sense to me (I guess by means of moving some lens group slightly), but what could "adjustments to the resolution power" mean? Anybody got any ideas?
After the second service attempt the bad FF was fixed, I still seem to notice a slight FF or BF, depending on the focal lenght. Also, I'm just wondering - is that also an expected behaviour, i.e. that different focal lenghts show FF or BF on the same lens?
Researching more into possible causes, I think I have (also) found out I got a focus shift issue, was able to reproduce as per <a class="" href="http://photography-on-the.net/forum/showthread.php?t=967488&page=3">http://photography-on-the.net/forum/showthread.php?t=967488&page=3</a> (message #38).
Anyway, for now it's ok - love the colours the lens produces in general, and some pictures without VC are really good and sharp, but unfortunately only a smaller amount of pics. And yes, I'm fully aware it's always the combination of a particular copy of a lens and particular body - in my case I had troubles, but will have to research a bit more how to compensate for all the flaws on my combo. Any more tips about the above appreciated 
All I can say: If I use the D750 or any other Nikon on AF-C, there's always a noise and movement when I relase the AF-Button and push it again. But of course, those screwdrive AF on (comparatively) cheap third party lenses are not the most precise mechanics.
Quote:All I can say: If I use the D750 or any other Nikon on AF-C, there's always a noise and movement when I release the AF-Button and push it again. But of course, those screw-drive AF on (comparatively) cheap third party lenses are not the most precise mechanics.
It's a FW problem within the lens, maybe I'll send it in, Jolu. Remember it's the Pentax mount.
Reverse engineering AF seems to cause quite a few problems, there are loads of complaints from those having AF accuracy problems with Sigma. One of the great things is practically all of my Nikon mount lenses are spot on and require no adjustment, on Pentax it's a story of -8;+5, -10 etc throughout the range!
Quote:Hey all - many thanks for all the replies! This may be a more complex problem than anticipated, but Dave might be right - I'll run another series of test shots with a tripod and different shutter speeds to see if it makes any difference over the next weeks when I find some time. Will report back.
The lens itself already had an oddyssey: I've come to a point where it's "ok" for my personal amateur photo purposes for now. I bought the Tamron new in Germany in April '15, noticed a bad front focus straight away. Back to shop (Media Markt), and they let me try another sample on my EOS 1000D, same issue, but competent sales guy that knew about the issue for a change.
Back in Ireland (where I live), contact Tamrom UK Support (Intro 2020 Ltd.) and they honoured the warranty no problems. Sent lens & body in, came back the same way, same front focus. Sent in to Tamron a second time, then they updated the lens firmware again, and also adjusted the following (copy & paste from Tamron UK Support): "the infinity point was moved along with adjustments made to the resolution power.".
Now, with my basic optics & physics school days knowledge moving the infinity point somewhat makes sense to me (I guess by means of moving some lens group slightly), but what could "adjustments to the resolution power" mean? Anybody got any ideas?
After the second service attempt the bad FF was fixed, I still seem to notice a slight FF or BF, depending on the focal lenght. Also, I'm just wondering - is that also an expected behaviour, i.e. that different focal lenghts show FF or BF on the same lens?
Researching more into possible causes, I think I have (also) found out I got a focus shift issue, was able to reproduce as per http://photography-on-the.net/forum/show...488&page=3 (message #38).
Anyway, for now it's ok - love the colours the lens produces in general, and some pictures without VC are really good and sharp, but unfortunately only a smaller amount of pics. And yes, I'm fully aware it's always the combination of a particular copy of a lens and particular body - in my case I had troubles, but will have to research a bit more how to compensate for all the flaws on my combo. Any more tips about the above appreciated
I read a few of the bloggs from your link, Wow, there some that are really getting their knickers in a twist there!
OK, it's worth doing some tests if only to know where you stand in terms of shutter speeds/ AF etc.....good luck!
Hi - yes, this all seems to dive too much into the matter - I think the average normal user simply wanting to take good pictures shouldn't have to worry about focal issues, reasons for front/back focus, VC/IS/OC jittering and matching shutter speeds, etc. Why cannot manufactures (both original and third party) just do their homework and apply higher quality on their manufacturing with much lesser tolerances, etc? I don't think I have an overly high need for quality ... but at least I can expect my pictures to be sharp out of the camera. I wasted so much time on these issues already over the last half year I could've done more productive things like actually crafting good pictures. 
I'm wondering now - is any of this actually any better on the newer system cameras like Nikon's 1 series, Canon M mount, and othes .... i.e. are we seeing similar issues there as well with originial or mixing thid party lenses into the mix (where available?)
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