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08-21-2018, 06:23 AM   #1
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Autofocus issue with DA 17-70

Hi guys,

About a month ago I bought a DA 17-70 on sale but have some bizarre issue with the AF. When on the wide end (less than 21mm), the lens will often fail to AF. By this, I means that it will not even try to focus, it will simply do nothing, the camera (a K-3) only showing a flashing green hexagon in the viewfinder. And when it works, it does focus in a very slow step by step way, like shown in this video:

Strangely, under the same condition, the lens will AF just fine when used in Liveview:

The AF issue will happen in any situations, even one that should be very easy to focus on, like a landscape on a sunny day wich provides many targets for the AF to lock on. This will happens no matter AF mode is used, AF-S, AF-C, Auto 27 to single point and anything between. This will not happen with my other lenses at similar focal length (Tamron 17-50, DA 10-17), so I don't think the K-3 is the problem.

So, anyone has an idea on what may be going on ? Since the lens is under warranty, am I better to just send it for repair ?


Last edited by CarlJF; 08-21-2018 at 06:27 AM. Reason: Correct bad links
08-21-2018, 06:55 AM   #2
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The 17-70 is a KAF3 lens. SDM only...And it is well known for SDM failures...or it could be something else...send it in for repair...
08-21-2018, 07:23 AM   #3
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Repair
08-21-2018, 07:25 AM   #4
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Sorry hit enter too soon. Repair might make sense except for the fact it works in live view. Do you have another body to test with? I'm wondering if your focus sensor could be dirty.

08-21-2018, 07:43 AM   #5
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QuoteOriginally posted by UncleVanya Quote
Sorry hit enter too soon. Repair might make sense except for the fact it works in live view. Do you have another body to test with? I'm wondering if your focus sensor could be dirty.
No, I don't have another body to test it. But I guess that if the AF sensor was the issue, it would not be specific for the DA 17-70 when used at wide angle. Other lenses would have the same issue and the DA 17-70 would also have trouble at any focal length.

P.S.: But this make me think it's a good idea to blow some air on the AF sensor, just in case. Nothing to lose by trying it.

Last edited by CarlJF; 08-21-2018 at 07:49 AM.
08-21-2018, 08:47 AM   #6
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Try to clean the AF sensor. The DA17-70 has been a workhorse for me, but traditionally had issues locking, usually at the long end. Having said that, when I got the K3, it was like an entirely different lens, the focus was faster and I never had the issue of locking focus at any focal length.

If cleaning (check the contacts also) doesn’t work, use the warranty for repair or replacement. Working, it’s a great lens.
08-21-2018, 09:05 AM - 1 Like   #7
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QuoteOriginally posted by CarlJF Quote
No, I don't have another body to test it. But I guess that if the AF sensor was the issue, it would not be specific for the DA 17-70 when used at wide angle. Other lenses would have the same issue and the DA 17-70 would also have trouble at any focal length.

P.S.: But this make me think it's a good idea to blow some air on the AF sensor, just in case. Nothing to lose by trying it.
I agree not much negative in trying.
08-21-2018, 02:47 PM   #8
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Do you have any other lenses that are SDM, DC or PLM? If so, do they autofocus properly? I have a DA 17-70 (bought new) that had various autofocus issues, some similar to yours, some different, like slow to wake up and work. I kept it going for the last 5 years by using it or at least exercising it weekly or more. Last year, I was away for 3 weeks and I tried the lens when I returned and found the autofocus died completely. I am pondering repairing mine but checking prices on used ones it can be cheaper to buy a used one that what KEH and Precision are quoting for the repair. Meanwhile I bought a used, like new DA 16-85 last year for not much more that repairing my 17-70 and I like the 16-85 much better.

08-21-2018, 04:02 PM   #9
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Ok guys, I've cleaned the AF sensor with a blower and the problem is still there. When trying the lens, I've also noticed that the quick-shift sometime doesn't work as expected with the focus ring kind of locked in place. So, I think I will simply send the lens out for repair.


QuoteOriginally posted by jddwoods Quote
Do you have any other lenses that are SDM, DC or PLM? If so, do they autofocus properly? I have a DA 17-70 (bought new) that had various autofocus issues, some similar to yours, some different, like slow to wake up and work. I kept it going for the last 5 years by using it or at least exercising it weekly or more. Last year, I was away for 3 weeks and I tried the lens when I returned and found the autofocus died completely. I am pondering repairing mine but checking prices on used ones it can be cheaper to buy a used one that what KEH and Precision are quoting for the repair. Meanwhile I bought a used, like new DA 16-85 last year for not much more that repairing my 17-70 and I like the 16-85 much better.
Unfortunately, all my other lenses are screwdrive. But its behavior is quite predictable: will focus step by step between 17mm and 24mm but will work fine from 35mm and longer. The 16-85 was the lens I was looking for, but somewhat over my budget right now. Nevertheless, the DA 17-70 at 230$US new with warranty still feels like a good deal, even with its AF issues and having to send it back for repair.
08-21-2018, 06:46 PM   #10
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I think I found the confirmation that the lens has some serious electronic issue. When slecting pictures from this lens in Lightroom, I noticed that many if not most of them have the wrong focal lengths in the Exifs, most reported value being 36mm and 43mm. I've done a test shot at 17mm, look at the info on the camera and guess what, 43mm is reported not 17mm. Which also would explain some other strange things I experienced with this lens, but didn't tought they could be related: IBIS doesn't seem to be as efficient as it is usually, but I only tried a handful of shots and didn't conclude anything from them. Astrotracer wasn't able to follow stars the only time I tried it with this lens, but given the hit and miss nature of the astrotracer I conclude that it just wasn't a good night. But now, these issues make perfect sense.

So, I will definitely send the lens for repair. Thanks for your help!
08-21-2018, 07:40 PM - 1 Like   #11
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Yeah, you don’t have the usual problem associated with this lens. You simply seem to have a faulty lens. Hope the repair goes well!
08-21-2018, 09:33 PM - 1 Like   #12
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I really love the 17-70 optically. I'm glad you found the issue while under warranty and hope it works out well.
08-22-2018, 06:54 AM   #13
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QuoteOriginally posted by CarlJF Quote
I think I found the confirmation that the lens has some serious electronic issue. When slecting pictures from this lens in Lightroom, I noticed that many if not most of them have the wrong focal lengths in the Exifs, most reported value being 36mm and 43mm.
I had the same issue with the first version of 17-70 that I bought from keh.com. It would only report 43mm and would subsequently not AF. I got a second version which correctly reported focal length and did AF after a fashion, but never accurately, back focusing at some focal lengths and front focusing at others (all on a K-5iis). Very nice lens optically, however. Eventually, I replaced it with the DA 16-85.
08-22-2018, 08:42 AM   #14
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QuoteOriginally posted by northcoastgreg Quote
I had the same issue with the first version of 17-70 that I bought from keh.com. It would only report 43mm and would subsequently not AF. I got a second version which correctly reported focal length and did AF after a fashion, but never accurately, back focusing at some focal lengths and front focusing at others (all on a K-5iis). Very nice lens optically, however. Eventually, I replaced it with the DA 16-85.
I would love to see the 17-70 and 16-85 pitted against each other to show where each shines best.
08-22-2018, 09:11 AM - 1 Like   #15
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QuoteOriginally posted by UncleVanya Quote
I would love to see the 17-70 and 16-85 pitted against each other to show where each shines best.
There's one here, DA* 16-50 vs DA 16-85 and DA 17-70. It's in french but I guess Google Translate could do a decent of translating it in english or whatever other language you want.
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