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09-15-2014, 01:36 PM   #1
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DA* 16-50 autofocus randomly working

Hi everyone,

I just wanted some input on an issue I started having recently.

After much pondering, I purchased the controversial da* 16-50 about 3 week ago, brand new.

In the first little while, I've put it through various tests and tricked the autofocus, and overall I was pretty happy with it. Yes, it's a quirky lens, but the learning curve seemed worth it.

Without warning, or any other changes whatsoever, something strange started happening. The lens stopped focusing, but only some times.

I have a success rate of about 20% when pressing the AF button (I'm a bbf'er). The lens will mostly try to focus and stop, in a random position, with the AF indicator blinking in the viewfinder, or a red indicator in live-view.

Addly, it seems that, on some instances, the focus ring doesn't catch the focus scale in MF. I have to rotate the ring the other way, and then in the way I originally intended once it caught it. This points me towards a mechanical problem.

C$1,300 later... This was the 2nd of 2 lenses the store had. The first one was an complete lemon and the girl sent in back to Pentax! Yikes!

Cleaned the heck out of the glass, of course, and tried all the AF modes, all with the same result. Latest firmware installed.

Any input will be much appreciated!

Thank you!

09-15-2014, 01:44 PM   #2
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QuoteOriginally posted by pomabille Quote
Hi everyone,

I just wanted some input on an issue I started having recently.

After much pondering, I purchased the controversial da* 16-50 about 3 week ago, brand new.

In the first little while, I've put it through various tests and tricked the autofocus, and overall I was pretty happy with it. Yes, it's a quirky lens, but the learning curve seemed worth it.

Without warning, or any other changes whatsoever, something strange started happening. The lens stopped focusing, but only some times.

I have a success rate of about 20% when pressing the AF button (I'm a bbf'er). The lens will mostly try to focus and stop, in a random position, with the AF indicator blinking in the viewfinder, or a red indicator in live-view.

Addly, it seems that, on some instances, the focus ring doesn't catch the focus scale in MF. I have to rotate the ring the other way, and then in the way I originally intended once it caught it. This points me towards a mechanical problem.

C$1,300 later... This was the 2nd of 2 lenses the store had. The first one was an complete lemon and the girl sent in back to Pentax! Yikes!

Cleaned the heck out of the glass, of course, and tried all the AF modes, all with the same result. Latest firmware installed.

Any input will be much appreciated!

Thank you!
Could be the infamous SDM problem.
Mine did exactly that before failing altogether ... this lens is now "screw drive only" via a hack which can be found on this forum.
If that lens is fairly new, I would advise to send it back/bring it back to the seller for replacement (again?)

JP
09-15-2014, 01:59 PM - 1 Like   #3
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That's exactly the symptoms my DA50-135 had before failing completely. I presume that's the famous SDM failure. Mine was too late to return, but still under warranty so I got it fixed under warranty and it works great. Hopefully it lasts.
09-15-2014, 01:59 PM   #4
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After only three weeks, definitely a return to the store or at the very least get the store to send it in for repairs. Especially for a lens that has a known 'possible' issue which often start as you described your problem.

I don't know about your store but most of them will give you the option to return and refund your purchase within 30 days. And unless you are past your 1 year warranty (two if you bought with a credit card) it is not worth converting to screw drive yet, more so since your focus ring doesn't seem to catch 100%... the underlying problem is probably more than just the SDM motor failing.

09-15-2014, 02:43 PM   #5
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Thank you guys! Yeah, I had read about the SDM failure on here before purchase, so I took a 2-yr warranty extension, bringing it to 4 years altogether.

I would be interested to hear what the verdict is. I'll be sure to let you guys know what happens.
09-15-2014, 04:04 PM   #6
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Send it in for service. I did that and the techs fixed my lens and I had it back in a week. Very easy and fast. I made sure that I asked them to fully inspect it as well.

John
09-15-2014, 04:19 PM   #7
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I would recommend to return it for an outright exchange. Although you have a four-year warranty, why should a three-week old lens have to be sent for repair? Especially since the first one you looked at was dead in the shop.

- Craig
09-15-2014, 11:33 PM   #8
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Sorry to hear of the problem - it sounds like a mechanical issue from your description. As the others say send it back.

I was looking at buying one of these lenses but the SDM issue put me off - just too risky with me being in NZ (and local distribution at the time was so much more expensive than USA). Its great you can take it back to the shop.

Really hope new Pentax lenses continue with DC AF or a new SDM II or something, so that people are more likely to trust it.

09-16-2014, 02:57 AM   #9
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QuoteOriginally posted by pomabille Quote
Hi everyone,

I just wanted some input on an issue I started having recently.

After much pondering, I purchased the controversial da* 16-50 about 3 week ago, brand new.

In the first little while, I've put it through various tests and tricked the autofocus, and overall I was pretty happy with it. Yes, it's a quirky lens, but the learning curve seemed worth it.

Without warning, or any other changes whatsoever, something strange started happening. The lens stopped focusing, but only some times.

I have a success rate of about 20% when pressing the AF button (I'm a bbf'er). The lens will mostly try to focus and stop, in a random position, with the AF indicator blinking in the viewfinder, or a red indicator in live-view.

Addly, it seems that, on some instances, the focus ring doesn't catch the focus scale in MF. I have to rotate the ring the other way, and then in the way I originally intended once it caught it. This points me towards a mechanical problem.

C$1,300 later... This was the 2nd of 2 lenses the store had. The first one was an complete lemon and the girl sent in back to Pentax! Yikes!

Cleaned the heck out of the glass, of course, and tried all the AF modes, all with the same result. Latest firmware installed.

Any input will be much appreciated!

Thank you!
If you send it in for repair insist on the new motor and circuit board!
06-10-2015, 09:00 AM   #10
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A bit late in the game on this thread, but mine has been acting up recently. The autofocus works well around 50% of the time, but the other 50% I will half-press the shutter and it won't do a thing. I tried the rear-focus button and the same thing - about 50% of the time it works.

Not sure what the issue is, but I'm planning on taking it in when I am back in Canada in a few weeks (still living in Haiti). Any idea how much a fix would cost to sort out this autofocus issue? Obviously it depends on the problem, but a ball-park would be helpful so I can brace myself financially!

Thanks!
06-10-2015, 09:14 AM   #11
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Hi jbriginshawphotograp,

It seems that you are another victim of the SDM motor failure. Mine started shortly after the return period was over in similar ways, and on top of that I also experienced blockage of the focus ring and other symptoms.

Is your lens still under warranty? If it is, I would recommend sending it for repair. If not, I'm not sure how much it would cost to replace it but I don't think it would be worth it.

Just to warn you though: I brought my lens back to the shop where I bought it for warranty repair in October, and it was shipped back in March. This is how long it took. On top of that, when I got the lens back, the window over the focusing scale was cracked and the shop refused to take responsibility for it.

I hope things turn out better for you.
06-10-2015, 09:26 AM   #12
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Yikes! Mine definitely is not still under warranty. I guess Ill wait and see what they quote me :S
06-10-2015, 09:33 AM   #13
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Sorry to hear that... I am just curious... how do you keep/store the lens when it is not in use? When I am not using the lens, I store them upright (front element down), never had a problem with either my 16-50 or 50-135 lenses. I guess if you leave it attached to the camera, you have no choice, meaning that the lens will be kept horizontal all the time. My 50-135 lens previously had SDM problems (that's when I kept the lens attached to camera) which has since been replaced. Since then, I always detached the lens from my camera when not in use and stand it up-side-down, and I haven't had any problems yet (crossing my fingers). Could very well be a design flaw on the weight of the motor... but I just don't know enough; but hopefully it may help.
06-10-2015, 09:41 AM   #14
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Hey,
You're correct that I keep it attached to my camera most often. My 50-135 and 300 work great, and I keep them stood up for the most part (I suppose I could still do better...). Sigh... At least it works...half the time :P
06-10-2015, 11:10 AM   #15
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QuoteOriginally posted by jbriginshawphotograp Quote
A bit late in the game on this thread, but mine has been acting up recently. The autofocus works well around 50% of the time, but the other 50% I will half-press the shutter and it won't do a thing. I tried the rear-focus button and the same thing - about 50% of the time it works.
Not knowing which camera you have is not helping. If you have e.g. a K100D, it's definitely not a SDM problem. If it's a camera that supports SDM, there is a thread how to disable the SDM, so the lens becomes screw-drive only. Might be a solution (if the problem is SDM). Or buy a K100D (not Super)
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