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06-15-2017, 05:43 AM   #1
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Tamron lenses for Pentax - front focusing common?

I'm beginning to suspect that front-focusing on modern, K-mount Tamron lenses is a pretty common thing. I've had a new 28-75 f/2.8 and new 70-200 f/2.8, both of which front-focused beyond the limits of AF fine adjustment on both my K-3 and K-3II (on both bodies, most of my lenses require zero adjustment, with others requiring nor more than +/-5).

Today, I received a brand new Tamron 10-24 f/3.5-4.5 that also front-focuses. It's *almost* OK at -10 fine adjustment, but not quite. It's a nice lens, so I've decided to keep it - and I've already sent it off to Intro2020, Tamron's distributor and service centre here in the UK. They've successfully addressed other Tamron lenses for me, and I'm confident they'll sort this one out too.

This seems to be more than bad luck or coincidence, though. I'm wondering if Tamron's K-mount test rig at their manufacturing plant is slightly out of alignment... My Sony A-mount Tammies are absolutely spot on

I can't help thinking that some of the less-than-stellar reports for wide-open performance of Tamrons might be down to this. Since it was serviced, my 28-75 f/2.8 is perfectly good wide open (better at f/4, of course, but I happily shoot it at f/2.8)...


Last edited by BigMackCam; 06-15-2017 at 05:57 AM.
06-15-2017, 05:53 AM   #2
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My 28-75 front focuses on my K-30 but not on my K-3.
I have been trying to do the fix but I get so frustrated that i have not been able to solve it.
The 70-200 works perfect on both cameras. Even at f2.8.

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06-15-2017, 07:19 AM   #3
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Both of mine are spot on without adjustment on my K-3II
06-15-2017, 07:38 AM   #4
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QuoteOriginally posted by victormeldrew Quote
Both of mine are spot on without adjustment on my K-3II
Hmm... Maybe I'm just very, very unlucky. No sense buying a lottery ticket this week, then

06-15-2017, 08:36 AM - 1 Like   #5
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QuoteOriginally posted by BigMackCam Quote
Hmm... Maybe I'm just very, very unlucky. No sense buying a lottery ticket this week, then
Or maybe I should be getting one myself. I'm sure Tamron's QC may be somewhat more forgiving than other makers, but while that means you're more likely to need adjustment, and more likely to find the maximum is not enough....you're also still likely to not need it at all.

One thing I'd say about them, the reports suggest their warranty service is very good. So it's not the end of the world if you get a lemon...and once you have a good one, they're excellent lenses...and in the case of the 70-200 vs the Pantax equivalent, you'll have nearly enough change in your pocket to buy a K-1 to go with it.
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06-15-2017, 09:53 AM   #6
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QuoteOriginally posted by victormeldrew Quote
One thing I'd say about them, the reports suggest their warranty service is very good. So it's not the end of the world if you get a lemon...and once you have a good one, they're excellent lenses...and in the case of the 70-200 vs the Pantax equivalent, you'll have nearly enough change in your pocket to buy a K-1 to go with it.
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I agree

I have been very unlucky... In addition to the K-mount 28-75, 70-200 and 10-24 that front-focused, the 28-75 for Minolta AF-mount I bought just after Christmas (to use on my Sony kit) had a tilted focal plane I didn't persevere with the 70-200, but both 28-75 lenses were promptly and professionally rectified by Intro2020, with each returning absolutely unmarked externally and spotlessly clean - and, most importantly, working perfectly.

I'd happily buy another Tamron lens - I really like them. But with my luck, I'm glad the distributor has such a good service centre!

Last edited by BigMackCam; 06-15-2017 at 10:03 AM.
06-15-2017, 10:53 AM - 1 Like   #7
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I haven't heard anything bad in particular that stands out regarding the D-FA lenses they make for Pentax.
06-15-2017, 10:55 AM   #8
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QuoteOriginally posted by mikesbike Quote
I haven't heard anything bad in particular that stands out regarding the D-FA lenses they make for Pentax.
That's a good point. I wonder whether they use the same manufacturing and test rig(s), or if they have a dedicated setup for the Pentax-branded models? Or perhaps the QC is just tighter on those...

06-15-2017, 12:57 PM - 1 Like   #9
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QuoteOriginally posted by BigMackCam Quote
I'm beginning to suspect that front-focusing on modern, K-mount Tamron lenses is a pretty common thing. I've had a new 28-75 f/2.8 and new 70-200 f/2.8, both of which front-focused beyond the limits of AF fine adjustment on both my K-3 and K-3II (on both bodies, most of my lenses require zero adjustment, with others requiring nor more than +/-5).

Today, I received a brand new Tamron 10-24 f/3.5-4.5 that also front-focuses. It's *almost* OK at -10 fine adjustment, but not quite. It's a nice lens, so I've decided to keep it - and I've already sent it off to Intro2020, Tamron's distributor and service centre here in the UK. They've successfully addressed other Tamron lenses for me, and I'm confident they'll sort this one out too.

This seems to be more than bad luck or coincidence, though. I'm wondering if Tamron's K-mount test rig at their manufacturing plant is slightly out of alignment... My Sony A-mount Tammies are absolutely spot on

I can't help thinking that some of the less-than-stellar reports for wide-open performance of Tamrons might be down to this. Since it was serviced, my 28-75 f/2.8 is perfectly good wide open (better at f/4, of course, but I happily shoot it at f/2.8)...
Both my 28-75 and 70-200 are spot on (no adjustments needed) on both my K-30 and K-70.
06-15-2017, 01:32 PM - 1 Like   #10
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Yeah, my 17-50, 28-75, 70-200 and 90 are all fine on my K-30, K-S2 and K-1.

I don't doubt the QC issues others have encountered, though ... all the big companies do less testing than they should and rely on customers to catch a proportion of the defectives.

Roger Cicala at Lens Rentals has lots of graphs showing the variation in his company's copies of even L Series Canon glass.
06-15-2017, 03:08 PM - 1 Like   #11
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QuoteOriginally posted by clackers Quote
Roger Cicala at Lens Rentals has lots of graphs showing the variation in his company's copies of even L Series Canon glass.
Indeed. Manufacturing variation within fine tolerances is not necessarily a QC fail.

Also always worth remembering that decent AF performance is a product of successfully pairing a camera body with a lens ... works like a lock and a key.

So in some instances you may see manufacturing variations in the body (eg in the lens mount or AF assembly) degrading the performance of a lens, not the lens degrading the body.
06-15-2017, 03:56 PM - 2 Likes   #12
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One of the inherent disadvantages of AF zooms is that calibrating fine focus can be problematic if the lens front focuses at one end of the range and back focuses at the other. Same goes with variations between near and far objects at a single focal length.

That said, in my limited experience with the Tamron lenses i've owned, the first copy of my 70-200/2.8 exhibited the problem and the second copy was and is within reasonable expectations. With any zoom, expect some compromises when relying on auto focus. good luck!
06-15-2017, 04:07 PM - 1 Like   #13
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I feel the pain with Tamron QC, I had 2 out of 2 new 70-200 I bought be de-centered, with left side of the frame soft. Tamron USA fixed it for me, but Tamron Canada didn't. Pity I lost the 6 year warranty with Tamron Canada to be able to fix mine in US.
06-16-2017, 04:53 AM   #14
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QuoteOriginally posted by rawr Quote
Also always worth remembering that decent AF performance is a product of successfully pairing a camera body with a lens ... works like a lock and a key.

So in some instances you may see manufacturing variations in the body (eg in the lens mount or AF assembly) degrading the performance of a lens, not the lens degrading the body.
In my case, I'm confident it's not the bodies... Out of all my Pentax branded lenses, the only ones that require any AF fine adjustment are my DA40 Limited (-2), DA70 Limited (+1), DA35 f/2.4 (-3) and FA50 f/1.4 (+2). The rest are all spot on at zero. These adjustments work the same on both my K-3 and K-3II, which suggests both bodies are remarkably close in calibration and tolerance.

After warranty service, my K-mount Tamron 28-75 still needs -4 adjustment, though I'm very happy with that.
06-16-2017, 04:57 AM - 1 Like   #15
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QuoteOriginally posted by mikeSF Quote
One of the inherent disadvantages of AF zooms is that calibrating fine focus can be problematic if the lens front focuses at one end of the range and back focuses at the other. Same goes with variations between near and far objects at a single focal length.

That said, in my limited experience with the Tamron lenses i've owned, the first copy of my 70-200/2.8 exhibited the problem and the second copy was and is within reasonable expectations. With any zoom, expect some compromises when relying on auto focus. good luck!
Indeed. I found that problem with the two copies of the 70-200 that I tried; the extent of front-focusing wasn't consistent across focal lengths, but in any case both samples were outside of the AF fine adjustment range for some or all focal lengths.

With the 10-24, I've informed the service centre that my priority is the wide end. I'd like it to be accurate at 10mm, hopefully through to around 15mm. It'd be great if it's spot-on all the way to 24mm, but I'll be happy if it's good from 10 - 15mm. In reality, I'll be using it at f/8 - f/11 most of the time anyway, so absolute spot on focus accuracy isn't critical - I'd just like the option of using it at wider apertures when necessary, especially at closer ranges...

Last edited by BigMackCam; 06-16-2017 at 05:18 AM.
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