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11-05-2009, 11:35 AM   #1
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Help! K200D + Tamron 17-50

Hello All,

I just picked a Tamron 17-50 for my K200D to boost the low light capability of my kit...

Pretty quickly I realised something was wrong, and after taking shots of a scale at a 45 degree angle, I could see that with AF it kept focusing a little before the point I was aiming at... with MF of course things were totally fine... with all the sharpness I expected from it...

So I went back to the shop and got another one... with exactly the same results... with AF it keeps focusing a little ahead of whatever I focus on...

Now this shop won't refund me, would rather send the lens to Tamron for repair etc...

So my question...

(1) is this something that a repair would fix, or is this a generic problem with the lens (since it happened across two samples)
(2) is there anything else that I can do to by pass this issue? I know with K20D etc you can customize AF... but I don't think that is an option with K200D...
(3) will the Sigma version be better in this regard? what are the trade-offs?

Otherwise, I think I would be forced to pick something else from the shop since I can't get my money back... I had avoided the DA*16-50 to avoid getting into such a trap with QC issues...

Any inputs will be appreciated...

11-05-2009, 01:29 PM   #2
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It's front focusing. It happened to me with two copies. The first merchant told me they had received a lot of bad copies recently, but I was inclined not to believe him. The second copy came with the same problem, and I resorted to the K200D HACK to adjust the focus. (Also, check out the 'debug mode' threads in this forum.) However, that resulted in back focusing at 17-20mm... I advise you to exchange the lens for something like Pentax 16-45 or 17-70, if you don't care too much about aperture 2.8. But first make sure your AF testing doesn't fool you. Compare the AF with other lenses.
11-05-2009, 02:15 PM   #3
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That's unfortunately normal behavior when shooting in light with a lot of long wavelength color (yellow, orange) in it. Meaning indoors under tungsten, halogen, some compact fluorescent, also outdoors around sunrise or sunset, etc. Virtually all DSLR's do this (an exception is the K-7, which has an additional sensor whose sole purpose is to correct for this effect).

So if you're seeing this under yellow/orange light, just accept it. Otherwise, most likely your camera's AF sensors aren't adjusted as well as they could be. Since the camera is probably not under warranty any more, rather than send it in for service, you might be better off using the "debug mode" method metioned above to workaroudn the problem.

I assume, BTW, you are shooting a test chart designed to present an unamiguous target for the AF system, as opposed to, say, a ruler, where the camera cannot read you mind and know which of those identical-looking horizontal lines you wanted it to focus on...
11-05-2009, 02:58 PM   #4
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Thanks for the responses so far...

Causey... I did parallel checks with the Pentax 18-250 (at 50mm to match the 50mm from the Tam 17-50) ... and also tried it with the Tamron 90... and these two focused very accurately...

Marc... yes, these tests were performed under what could be termed as yellow(ish?) light .. I guess i'll repeat them under normal daylight as well... but my whole point of a 2.8 zoom was low light indoor shots As for the focusing, I focused on the numbers... which are quite big and bold & printed parallel to (but distinctly enough) to the lines... and the 18-250 & Tamron 90 got the sharp focused shots on the first attempt... I also tested all three using some of the test charts available online... along with random close up shots of leaves etc (but yes, all indoors, under lights) ... the Tamron 17-50 with AF messed most of these vs. the other two...

I did read about the "hack" but if I do that, then won't the other lenses which focus correctly right now start to loose focus due to some form of compensation?

11-05-2009, 03:18 PM   #5
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In this pic, I have tried to show the results across the three lenses... in all the three cases I have used 15 as the focus point...

Last edited by rkt; 08-23-2010 at 12:44 PM.
11-05-2009, 03:19 PM   #6
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QuoteOriginally posted by rkt Quote
Causey... I did parallel checks with the Pentax 18-250 (at 50mm to match the 50mm from the Tam 17-50) ... and also tried it with the Tamron 90... and these two focused very accurately...


I did read about the "hack" but if I do that, then won't the other lenses which focus correctly right now start to loose focus due to some form of compensation?
Pentax 18-250mm has a max aperture of 4-4.5 around 50mm, so I think the Tamron 90mm is more relevant for observing the AF with a narrow DOF, similar to that of Tamron 17-50mm.

I tested both 'my' copies in artificial and natural light: the same result, over and over.

Another guess that I have is that there is something with K10D's and K200D's AF system--most complaints about AF-ing with Tamron 17-50mm come from owners of these two cameras.

With the hack you can enter the debug mode, adjust the AF for the time you use the Tamron 17-50mm, then go back to the initial settings... Or you can leave the camera in the debug mode and do quick adjustments after changing lenses. To be honest, I didn't like these solutions.
11-05-2009, 03:20 PM   #7
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QuoteOriginally posted by rkt Quote
In this pic, I have tried to show the results across the three lenses... in all the three cases I have used 15 as the focus point...
I think my second copy had an even more severe front focus... But it's very familiar. I'm sorry for this... It reminds me of my recent nervous testings and re-testings after noticing that many of my everyday shots weren't focused. Fortunately, I could return the lens.

Try to use a focusing chart in very good natural light with camera on a tripod. (But I suspect you'll have the same problem... Still just to make very sure.)
11-05-2009, 06:21 PM   #8
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QuoteOriginally posted by rkt Quote
In this pic, I have tried to show the results across the three lenses... in all the three cases I have used 15 as the focus point...
See my comments above. *You* might have wanted the camera to focus on the 15, but it has no way of knowing that. The AF sensor is much larger than the little red square in the viewfinder; it may well have simply chosen to focus on one of the closer lines. Plus, it looks like this is probably under tungsten light.

11-05-2009, 11:18 PM   #9
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Does this happen to all K200D paired with a tamron 17-50mm? I was thinking of getting this lens also to pair up with the K200D.. Whats the best solution for this kind of problem? are there any lense which has the same image quality and price of tamron 17-50mm?
11-06-2009, 03:18 AM   #10
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Causey... even I am not happy hacking the firmware to use a lens... that is why I think I will end up exchanging it for something else that I could use... maybe a 10-20 or 10-24 to go with the 18-250 for now... and I am completely in sync when you mention all the nervous testing ... I have been at it since last Saturday when I got the lens... and only decided to check further when I realised some simple shots around the house looked too soft for this lens's reputation... and have spent all subsequent evenings doing just this... hoping to prove myself wrong and therefore keeping the lens... but it seems very unlikely... unless I only use MF at 2.8 ... which I cannot accept when buying a new AF lens

Marc... I would assume the digits are sufficiently distinct for the K200D AF sensor... otherwise... at the same aperture (2.8) shouldn't the Tam 90 have shown some focussing issues as well? But, apart from that, I used some charts that I downloaded as well... and used a tripod to do the tests... with the charts printed and pasted flat on a wall... and of the three lenses... only Tam 17-50 seemed to be focussing elsewhere... after the chart, I also took handheld shots of individual objects like my table lamp switch... a dried leaf... and such... but all with the same result...

rustynail925... I would assume the answer is yes... I was so caught up with the DA* variant and the QC issues that I slacked a bit on researching this lens w.r.t. K200D but it seems to be fairly frequent... (even the forum lens review section has some users reporting FF issues... and since I think you can compensate for this in a K20D or K7 you can get around it... but not so for the K200D atleast...) The Sigma version is another choice (if you leave out the DA*) ... but I am yet to receive any feedback on Sigma vs. Tamron IQ etc... hopefully someone responds to Q.3. in my original post...
11-06-2009, 03:51 AM   #11
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Maybe its worth the risk since the DA* is about $300-400 more. You can get a newer body like a K-m to pair it with at the same cost of the DA*
where did you get your tamron? and was it made in japan?
11-06-2009, 05:54 AM   #12
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Yup, it was (is) made in Japan (as per the text on the lens body)... I picked it up locally in Munich (Germany) ...

I would love to upgrade the camera body as well, but after the whole 'lens business' over the last weeks... first all the fretting and deciding, then buying, and then cribbing about the AF issues... my wife might throw me out of the house now

The K20D body is going for EUR 699... and with the AF adjustments available in it... I am truly tempted! The DA* is going at EUR 949 ... while the Tamron was EUR 349... I wish I could buy at US prices... I checked Camera Central prices... and the DA* converted to EUROs would come for about EUR 480 !! Not fair...
11-06-2009, 06:11 AM   #13
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rkt, IMO the focusing charts you can download and print are virtually worthless from a precision perspective. The target area is simply too small. As Marc already mentioned there is no way you can know precisely what the camera has chosen to focus on.

Although I am not advocating or endorsing its use, something like a LensAlign is much more accurate for determining correct focus. Personally I believe LensAlign is way overpriced. There is a thread in the accessories subforum that shows a simple setup to duplicate nearly all of the LensAlign features, using common household items.

In your case it does appear that you have done this test multiple times with different charts, the likelyhood of multiple tests producing inaccurate results every time is highly unlikely so I would also agree that your Tamron lens front focuses.
11-06-2009, 06:23 AM   #14
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QuoteOriginally posted by rustynail925 Quote
Does this happen to all K200D paired with a tamron 17-50mm? I was thinking of getting this lens also to pair up with the K200D.. Whats the best solution for this kind of problem? are there any lense which has the same image quality and price of tamron 17-50mm?
I have no idea--when looking for answers to my own problem I just noticed that generally it was the owners of K10D and K200D who expressed complaints. But this is a known problem for other camera brands as well.

Some people say that Pentax 16-45mm is comparable; other say it's not. I haven't tried it myself, but I looked at full sized pictures on flickr and Tamron seems significantly better. It's really a superb lens... if you get a good copy, or if your copy works with your type of camera body, or if, as Marc says, if the sensor of your camera is well put in place...
11-06-2009, 06:26 AM   #15
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QuoteOriginally posted by rkt Quote
Causey... even I am not happy hacking the firmware to use a lens... that is why I think I will end up exchanging it for something else that I could use... maybe a 10-20 or 10-24 to go with the 18-250 for now... and I am completely in sync when you mention all the nervous testing ... I have been at it since last Saturday when I got the lens... and only decided to check further when I realised some simple shots around the house looked too soft for this lens's reputation... and have spent all subsequent evenings doing just this... hoping to prove myself wrong and therefore keeping the lens... but it seems very unlikely... unless I only use MF at 2.8 ... which I cannot accept when buying a new AF lens
I know what you're saying...
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