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07-02-2014, 06:43 AM   #1
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K5 ii + Tammy 17-50 2.8 Issues

Just picked up the infamous Tammy 17-50 2.8 and pretty disappointed. Wondering if I can get some feedback from existing owners.

I'm seeing a few issues with the copy of the lens I have:

1. It's missing focus a bit and I needed to dial in an AF adjustment to make it better. At one point I used the dot focus method after MF and a range of +5 to -7 all locked (is such a wide range normal?) so I used a subjective method to pick the best point instead.

2. Focusing using CDAF through live view is even more inaccurate than PDAF through the viewfinder.

3. The camera refocuses slightly between F2.8-4.5 and F5.6+. With the adjustment I have dialed in right now it misses focus at F5.6.

4. Seems softer than expected at F2.8...

I have attached two images. The 3 image set is the same lens with a Sony mount from a review - it's the type of performance I was expecting. The 4 image set is my copy.

Oh, and my lens is stamped "Made in China" if that makes any difference.

I guess the question is, do I return it? Try to get another copy? send it in Tamron for service? or am I being too picky?

Thanks,
Rob

Attached Images
   
07-02-2014, 06:59 AM - 1 Like   #2
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Send it back and exchange for a Sigma 17-50 F2.8
07-02-2014, 07:05 AM   #3
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My copy on the K5 is nice and quite sharp. I'd probably send it in under warranty.
07-02-2014, 08:09 AM   #4
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QuoteOriginally posted by tommystery Quote
or am I being too picky?
You may also simply not be testing properly. There are articles in these forums about how to do so.

Maybe do some more testing before sending it back, if only so that you can be sure that lens copy #2 (if thats what you get) works back better than copy #1.

Having said that, my Tamron 17-50 needs, if I recall, about -4 on my K-3 for good results. But on my K-5 it needed no adjustment. And on the K-x it worked very well. So lenses will often need some AF adjustment, depending on how the lens works with the body.

The first copy I received of my Tammy 17-50 was badly de-centred (one side WAY more blurry than the left), possibly due to receiving some shock in transit, and so it had to be returned. So dud lenses do happen. If your pain persists, send it back.

07-02-2014, 06:51 PM   #5
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Hey guys,

Appreciate the responses. Unfortunately getting the Sigma is not really an option. The only ones that I've seen available up here are grey market from Japan and I'd have to special order. Based on the reviews I've seen I'm not convinced that this lens is any better either.

I did some more testing today and settled on a micro AF value of -8 based on focusing at F2.8@50mm. This value works across the FL.

In the attached sample (100% crops) I refocused at each aperture setting and these results are repeatable.

F2.8 - as sharp as it's going to be, even MF
F3.2 - good
F3.5 - even better
F4.0 - deteriorating
F4.5 - worse
F5.0 - even worse
F5.6 - good

If I don't refocus at every F-stop the camera refocuses (incorrectly) at F4.0 or F4.5 and then again at F5.6.

I'll give Amplis a call tomorrow and see what they have to say - I don't think that there are any other repair center options up here north of the border.
Attached Images
 
10-22-2014, 12:51 PM   #6
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It is lens. I had similar issues with K-x and that is why i now have 16-45 wich works great.
10-25-2014, 04:55 PM   #7
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QuoteOriginally posted by tommystery Quote
Just picked up the infamous Tammy 17-50 2.8 and pretty disappointed. Wondering if I can get some feedback from existing owners.

I'm seeing a few issues with the copy of the lens I have:

1. It's missing focus a bit and I needed to dial in an AF adjustment to make it better. At one point I used the dot focus method after MF and a range of +5 to -7 all locked (is such a wide range normal?) so I used a subjective method to pick the best point instead.

2. Focusing using CDAF through live view is even more inaccurate than PDAF through the viewfinder.

3. The camera refocuses slightly between F2.8-4.5 and F5.6+. With the adjustment I have dialed in right now it misses focus at F5.6.

4. Seems softer than expected at F2.8...

I have attached two images. The 3 image set is the same lens with a Sony mount from a review - it's the type of performance I was expecting. The 4 image set is my copy.

Oh, and my lens is stamped "Made in China" if that makes any difference.

I guess the question is, do I return it? Try to get another copy? send it in Tamron for service? or am I being too picky?

Thanks,
Rob
Do what FelixKH suggested. I ordered the Tamron 17-50 from Amazon and, no matter what FF/BK adjustments I made, it just wouldn't focus properly. I sent mine back and ordered the Sigma from B&H. This is a documented issue with Tamrons (at least this one). Heck, I tried to order a Tamron 28-75 because that one's been highly touted for years. It was stolen in-transit. Thus, my 17-50 order. Guess it wasn't meant to be. Get Tamron to fix it, sell it and then pay a little extra for shipping from B&H. By the way, I'm very happy with the Sigma. Would have been nice if it were weather-sealed and had the extremely handy lens hood with the removable window but... such is the life of a Pentax owner in their search for affordable, quality lenses.
10-28-2014, 04:47 PM   #8
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One must love this forum. If you have an issue, someone already has had it to.
I have found that I get the correct focus if at f/2.8 to f/5.0. If I dial in f/5.6 or higher it changes the focus to become front focused.
So I set focus with f/5.0 or lower, change to f/8 and shoot. I use back button focus so there will be no change in focus.

I really hate having to do workarounds but the lens is sharp from center to edge so I live with it since the price is really low.

If using live view and stopping down to for instance f8 and using manual focus there are weird going ons when trying to focus...

If someone has a fix, please let me know.

I have had it in for service and they fixed the back focus I had but the weird change of focus when going to f5.6 or higher they do not seem to have a new lens firmware for...

10-28-2014, 05:20 PM   #9
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QuoteOriginally posted by Tjompen1968 Quote
One must love this forum. If you have an issue, someone already has had it to.
I have found that I get the correct focus if at f/2.8 to f/5.0. If I dial in f/5.6 or higher it changes the focus to become front focused.
So I set focus with f/5.0 or lower, change to f/8 and shoot. I use back button focus so there will be no change in focus.

I really hate having to do workarounds but the lens is sharp from center to edge so I live with it since the price is really low.

If using live view and stopping down to for instance f8 and using manual focus there are weird going ons when trying to focus...

If someone has a fix, please let me know.

I have had it in for service and they fixed the back focus I had but the weird change of focus when going to f5.6 or higher they do not seem to have a new lens firmware for...
You're a far better - and smarter - man than I, Tjompen. That procedure just to take a picture would drive me nuts. One thing about the Tamron lens that I admired in the short time that I owned it... the colors were deep and rich even though they were out of focus.
10-28-2014, 05:34 PM   #10
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QuoteOriginally posted by SlamDesiAK Quote
You're a far better - and smarter - man than I, Tjompen. That procedure just to take a picture would drive me nuts. One thing about the Tamron lens that I admired in the short time that I owned it... the colors were deep and rich even though they were out of focus.
Tommystery... Here's a photo taken with my K5IIs and a Sigma 17-50. If it makes any difference, I had a circular polarizer on at the time. PS: not my dogs. (I'm not good at this so, if there's no photo, I'll have to consult the manual.)
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PENTAX K-5 II s  Photo 
10-28-2014, 05:51 PM   #11
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My Tamron 17-50 works great on my K5 since I sent it in to cleaning and repair. One of the elements was slightly out of alignment. Works better than new now!
10-29-2014, 11:33 AM - 2 Likes   #12
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Hi guys,

Just wanted to post an update with my experiences since there's been a renewed interest in this thread and I'm sure that others are wondering how things turned out.

I had purchased the lens from Carman's Foto Source (prodigital2000) online and got it serviced by Amplis under warranty. Both went above and beyond to make sure that I was taken care of. Amplis serviced the lens a total of three times and Carman's always told me that we could work something out if I wanted to try something else - in the end I kept it.

One of the problems with PDAF is that the camera relies on the lens firmware to go to the instructed focal distance. So if the camera measures that the subject is 3' away but the lens erroneously focuses to 2.5' the subject will be out of focus. In most modern DSLRs (including Pentax) this process is double checked against what the lens reports so if there is a large error the camera will attempt to refocus or throw an error. One issue, is that the K5 ii has a high tolerance and will confirm focus even if it is about +/- 6 micro-AF equivalent points out of focus. You can confirm this by using the dotTune method to set micro-AF.

Another problem is that the Tammy suffers from focus shift. Tamron knows about this and that's why the lens refocuses at >F5.6, Amplis even confirmed with Tamron Japan that this is the correct behavior. What they won't admit to is that the problem is more complex. After I received the lens for the second time I noticed that it focused perfectly in situations where the subject was < 1' away. At > 3' I could get more accurate focus by focusing at F5.0, holding focus and then stopping down before taking a photo. I suspect that the setting for the adjustment is linear across all focal distances and doesn't completely fit the characteristics of the lens - the tech here couldn't do anything to change this.

So why did I decide to keep the lens?

I went to Henry's at one point and used their 35mm 2.4 to snap some comparison pics. I had the Tammy with me so did a direct comparison, it came out far ahead. I started reading more about how PDAF works and found people having issues with gear across different systems that cost exponentially more, the sentiment being that you could only perfectly adjust the lens to a specific focal length. One user with Canon L glass commented that he had to set micro AF between -6 or +9 if he was shooting at 24mm or 35mm; at least the Tammy was consistent!

But the thing that really put my mind at ease was testing the Tammy with my old Kr. All of a sudden everything I was seeing with the K5 seemed to disappear - but you see, it didn't. It was the lower resolution of the Kr that was making the lens's quirks almost invisible. So I stopped pixel peeping, shoot more and find that I sleep much better at night.

The Tammy 17-50 2.8 is an incredible value and the sharpest lens that I have ever owned. If I'm focusing in an extremely critical situation I'll flip over to MF and squeeze every bit of resolution out of it. I also no longer believe that any lens can focus perfectly. A lot of people have suggested getting the Sigma, maybe it would be slightly better, but to get one with Canadian warranty would cost me almost double what I paid for the Tammy and that lens has it's own issues as well.

I hope that this post is helpful.

Cheers,
Rob

Last edited by tommystery; 10-29-2014 at 11:42 AM.
11-18-2014, 01:26 PM   #13
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QuoteOriginally posted by tommystery Quote
Hi guys,

Just wanted to post an update with my experiences since there's been a renewed interest in this thread and I'm sure that others are wondering how things turned out.

I had purchased the lens from Carman's Foto Source (prodigital2000) online and got it serviced by Amplis under warranty. Both went above and beyond to make sure that I was taken care of. Amplis serviced the lens a total of three times and Carman's always told me that we could work something out if I wanted to try something else - in the end I kept it.

One of the problems with PDAF is that the camera relies on the lens firmware to go to the instructed focal distance. So if the camera measures that the subject is 3' away but the lens erroneously focuses to 2.5' the subject will be out of focus. In most modern DSLRs (including Pentax) this process is double checked against what the lens reports so if there is a large error the camera will attempt to refocus or throw an error. One issue, is that the K5 ii has a high tolerance and will confirm focus even if it is about +/- 6 micro-AF equivalent points out of focus. You can confirm this by using the dotTune method to set micro-AF.

Another problem is that the Tammy suffers from focus shift. Tamron knows about this and that's why the lens refocuses at >F5.6, Amplis even confirmed with Tamron Japan that this is the correct behavior. What they won't admit to is that the problem is more complex. After I received the lens for the second time I noticed that it focused perfectly in situations where the subject was < 1' away. At > 3' I could get more accurate focus by focusing at F5.0, holding focus and then stopping down before taking a photo. I suspect that the setting for the adjustment is linear across all focal distances and doesn't completely fit the characteristics of the lens - the tech here couldn't do anything to change this.

So why did I decide to keep the lens?

I went to Henry's at one point and used their 35mm 2.4 to snap some comparison pics. I had the Tammy with me so did a direct comparison, it came out far ahead. I started reading more about how PDAF works and found people having issues with gear across different systems that cost exponentially more, the sentiment being that you could only perfectly adjust the lens to a specific focal length. One user with Canon L glass commented that he had to set micro AF between -6 or +9 if he was shooting at 24mm or 35mm; at least the Tammy was consistent!

But the thing that really put my mind at ease was testing the Tammy with my old Kr. All of a sudden everything I was seeing with the K5 seemed to disappear - but you see, it didn't. It was the lower resolution of the Kr that was making the lens's quirks almost invisible. So I stopped pixel peeping, shoot more and find that I sleep much better at night.

The Tammy 17-50 2.8 is an incredible value and the sharpest lens that I have ever owned. If I'm focusing in an extremely critical situation I'll flip over to MF and squeeze every bit of resolution out of it. I also no longer believe that any lens can focus perfectly. A lot of people have suggested getting the Sigma, maybe it would be slightly better, but to get one with Canadian warranty would cost me almost double what I paid for the Tammy and that lens has it's own issues as well.

I hope that this post is helpful.

Cheers,
Rob
Thanks for that, I've been eyeing the 17-50 for awhile, and is now only second inline to the 28-75 for my future purchases.
11-21-2014, 03:01 PM   #14
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Interesting thread. I have a Tamron 17-50 I purchased back when I was using the K10d (probably purchased around 2008). I really like the lens and have not had any of the problems mentioned. Perhaps I was lucky or perhaps these problems are happening in newer lenses.

I was so happy with mine that I purchased a couple of other Tamron lenses. The 10-24 has been nice, but not as sharp as my 17-50. The 17-50 stays nice and sharp all the way to f11 although it peaks around f5.6. It makes me worried if I ever needed to replace it. I'll have to really work hard to keep it in good shape if I am indeed one of the few lucky ones with a good performing 17-50 from Tamron.
11-21-2014, 03:51 PM   #15
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QuoteOriginally posted by emalvick Quote
Interesting thread. I have a Tamron 17-50 I purchased back when I was using the K10d (probably purchased around 2008). I really like the lens and have not had any of the problems mentioned. Perhaps I was lucky or perhaps these problems are happening in newer lenses.

I was so happy with mine that I purchased a couple of other Tamron lenses. The 10-24 has been nice, but not as sharp as my 17-50. The 17-50 stays nice and sharp all the way to f11 although it peaks around f5.6. It makes me worried if I ever needed to replace it. I'll have to really work hard to keep it in good shape if I am indeed one of the few lucky ones with a good performing 17-50 from Tamron.
And you are using it on a K-5II or K-3?
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