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08-06-2017, 11:36 PM   #1
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K-3 with the 17-50mm f/2.8

Hi there,

I just recently purchased a Sigma 17-50mm f/2.8 based on reviews that I read on several forums, including this one. I received my copy of the lens in the mail last night, and as excited as I was, my excitement was short lived as the lens does not focus, it doesn't hunt or anything but it just fails to focus the subject whatsoever, it will at times focus the foreground, sometimes the background but never the subject.

I have been very disappointed as I live in the middle east and shipping in and out of this region is expensive, so for me to ship this lens back to the vendor is pretty useless as it will, a) take forever to get to Japan and b) will cost me $100 at least, that's 1/3rd the cost of the lens.

Is there a workaround? Fingers crossed, I'm hoping that one of you guys can help me out. The lens locks on to the subject really quick but its out of focus.

I currently use a 50mm f/1.4, a 50-200mm f/4-5.6 (Got this lens together with the Camera as the kit lens wasn't available at the time of purchase), both Pentax and they work fine, never miss focus. So the 17-50mm was the ideal lens for wide-angle.

Is there anyway to fix the problem without having to return the lens?

Any help would be much appreciated!.

08-06-2017, 11:41 PM   #2
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Hi AIW. Here is a link to a Pentax forums tutorial on focus issues. Give it a look ( and a try ) to see if it helps. Good luck.


Fixing Front and Back Focus - Introduction - In-Depth Articles
08-06-2017, 11:49 PM   #3
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QuoteOriginally posted by pjv Quote
Hi AIW. Here is a link to a Pentax forums tutorial on focus issues. Give it a look ( and a try ) to see if it helps. Good luck.


Fixing Front and Back Focus - Introduction - In-Depth Articles
Thanks for link, I'll give it a read, but do you think that this problem can be solved without having to return the lens? As that is my biggest concern right now.
08-07-2017, 12:00 AM   #4
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QuoteOriginally posted by AIW Quote
Thanks for link, I'll give it a read, but do you think that this problem can be solved without having to return the lens? As that is my biggest concern right now.
Testing your lens EXACACTLY as described in the link, and making any adjustments will be your only guide I think. The settings on your camera, the lighting, the focus points used etc, all play a part in getting good focus. Camera technique can also play a part. If you have a good tripod, do some testing and see how the lens performs. If you still have problems after doing some tests, post some images with the EXIF data in tact, and the method you used for taking the photograph eg, tripod, handheld etc. Good luck with your testing.

08-07-2017, 12:21 AM   #5
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QuoteOriginally posted by pjv Quote
Testing your lens EXACACTLY as described in the link, and making any adjustments will be your only guide I think. The settings on your camera, the lighting, the focus points used etc, all play a part in getting good focus. Camera technique can also play a part. If you have a good tripod, do some testing and see how the lens performs. If you still have problems after doing some tests, post some images with the EXIF data in tact, and the method you used for taking the photograph eg, tripod, handheld etc. Good luck with your testing.
Thanks! Will try it out and get back to you with photos.
08-07-2017, 04:39 AM - 1 Like   #6
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Remember, on Pentax, we have an AF switch on the body, AND The Sigma / DA* lenses also have an AF switch on the lens.

If you are not getting lens motor movement at all, verify the switches are ON.
08-07-2017, 10:46 AM   #7
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QuoteOriginally posted by AIW Quote
I just recently purchased a Sigma 17-50mm f/2.8
As a happy owner of a Tamron 17-50mm f/2.8,
I'm not sure that I'd consider a Sigma lens to be the 17-50mm f/2.8!

08-07-2017, 12:59 PM   #8
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QuoteOriginally posted by Blacknight659 Quote
Remember, on Pentax, we have an AF switch on the body, AND The Sigma / DA* lenses also have an AF switch on the lens.

If you are not getting lens motor movement at all, verify the switches are ON.
Its kind of confusing this!, having to deal with two AF switches, but to answer your question, the AF mode is on and the motor is working, however, the lens just fails to focus on the wide end, and focuses somewhat well when zoomed in @ 50mm.

---------- Post added 08-07-17 at 01:07 PM ----------

QuoteOriginally posted by lytrytyr Quote
As a happy owner of a Tamron 17-50mm f/2.8,
I'm not sure that I'd consider a Sigma lens to be the 17-50mm f/2.8!
Everyone that I talked to, recommended the Sigma over the Tamron, lol,
08-07-2017, 05:39 PM   #9
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QuoteOriginally posted by AIW Quote
the lens just fails to focus on the wide end, and focuses somewhat well when zoomed in @ 50mm.
There are two options in that situation:
Focus at 50mm, then zoom out to wide,
or use live view to focus at the wide end.
08-08-2017, 02:54 AM   #10
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You've got a dud lens. Mine is sharp wide open. I have used it at events and weddings. It's a go to lens in my opinion.

Last edited by howieb101; 08-08-2017 at 02:55 AM. Reason: Typo
08-09-2017, 04:17 AM   #11
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QuoteOriginally posted by lytrytyr Quote
There are two options in that situation:
Focus at 50mm, then zoom out to wide,
or use live view to focus at the wide end.
Live view drains so much battery, lol.

---------- Post added 08-09-17 at 04:20 AM ----------

QuoteOriginally posted by AIW Quote
Live view drains so much battery, lol.
That seems to be the case unfortunately and to makes matters worse, I went to local Sigma dealer and they said that the lens requires a firmware and since Pentax pretty much doesn't sell at all here, they do not keep the dock for Pentax mount required to update the lens firmware. I don't know how much of that is true.
08-09-2017, 05:55 AM   #12
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QuoteOriginally posted by AIW Quote
Its kind of confusing this!, having to deal with two AF switches, but to answer your question, the AF mode is on and the motor is working, however, the lens just fails to focus on the wide end, and focuses somewhat well when zoomed in @ 50mm.

---------- Post added 08-07-17 at 01:07 PM ----------



Everyone that I talked to, recommended the Sigma over the Tamron, lol,
Ok, sure sounds like a dud. I would contact SIGMA for repair service. Explain the situation and see if they can help you out with shipping. Otherwise, contact the seller and try to get a refund.
08-09-2017, 08:06 AM   #13
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QuoteOriginally posted by AIW Quote
Live view drains so much battery, lol.
It only takes a second or two to focus.

And the battery type you have in the K3
has no problem powering the permanent live view in my K-01 cameras.
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