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07-26-2017, 07:22 PM   #1
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DA* 16-50 Stiff Zoom Ring

Hello all,

I purchased a Pentax 16-50 DA* off the bay, and moving the zoom ring seems abnormally stiff from 28-45mm. The lens does zoom, and seems to be ok otherwise, but it isn't comparable to my other lenses or my DA* 50-135.

Should I be worried about this? Does your copy have a stiff action in the zoom range?

07-26-2017, 09:22 PM   #2
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sounds like a gasket could have come loose and is adding friction at that point in the zoom range.
07-27-2017, 04:40 AM   #3
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QuoteOriginally posted by dcshooter Quote
A super common problem with this lens is for the plastic attachment on the outer ring that hooks to the inner zoom lever to begin to break. Stiffness like what you describe is often an early manifestation of this problem. Unfortunately, this usually requires replacement of the entire outer zoom ring, since it's a solid piece of molded polycarbonate.

I did some more testing, perhaps this will help with the diagnosis.

- When pointing the lens up, and zooming from 50-16mm (moving with gravity), The zoom action is smooth. It seems the weight of the optics are removing some of the tension when collapsing the lens.

- When I point the lens down and zoom from 50-16mm (moving against gravity), there is noticeable tension from 40-28, almost a plastic on plastic feeling.

- When the lens is level, I notice some some general tension but not as bad as point the lens up or down. Also, I notice the same tension issues when I revers this test (16-50mm pointing the lens up).

They buyer said the lens was in perfect condition. I am starting to think it isn't.
07-27-2017, 04:47 AM   #4
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Not everyone places consideration to those finer details to lenses, hence the discrepancy.
But I do recall this little issue with a 16-50 I had, and indeed it didn't affect function, but it was occasionally annoying to have to put extra effort to zoom in (my tightness was both ways). I'm not sure much can be done about it, a precision tool will have very small tolerances and fixing it may risk it not being the same again.

07-27-2017, 04:56 AM   #5
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QuoteOriginally posted by Ash Quote
Not everyone places consideration to those finer details to lenses, hence the discrepancy.
But I do recall this little issue with a 16-50 I had, and indeed it didn't affect function, but it was occasionally annoying to have to put extra effort to zoom in (my tightness was both ways). I'm not sure much can be done about it, a precision tool will have very small tolerances and fixing it may risk it not being the same again.
I am wondering if I should return the lens especially if this will be a problem in the future. Should I expect a good copy of this lens to be free of this tension, or is this par for the course?

The seller did show a document stating the lens was repaired in 2017 for SDM and misalignment issues. I was hoping someone would say new lenses have this tension, and after some time it will go away. I am starting to think it has a flaw that wasn't disclosed.
07-27-2017, 05:34 AM   #6
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QuoteOriginally posted by Blacknight659 Quote
Hello all,

I purchased a Pentax 16-50 DA* off the bay, and moving the zoom ring seems abnormally stiff from 28-45mm. The lens does zoom, and seems to be ok otherwise, but it isn't comparable to my other lenses or my DA* 50-135.

Should I be worried about this? Does your copy have a stiff action in the zoom range?
Mine does this to. The zoom will probably break.

I live in a country with basically nonexistent servicing, and I could manage to fix it by my own.(I do a lot of DIY repair in mine equip)

Like some already said, a very little and tiny and fragile plastic index tab connects the ring with the helicoids of the zoom group and are quite prone to break. A very fragile and bad engineering in my opinion.

I did relpace it with a custom made steel index tab and now are working good.


I recomend you to take it to service right away, because if it is already that stiff, it'll break soon. And mostly in a situation that will piss you off.

But if you could return it or make some sort of compensation, give it a try with the seller.
07-27-2017, 09:11 AM   #7
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I received a brand new 16-50 from Pentax and it has the same stiffness.

07-27-2017, 10:08 AM   #8
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QuoteOriginally posted by wtlwdwgn Quote
I received a brand new 16-50 from Pentax and it has the same stiffness.
Mine just did broke with about a year and half use.

My brother send it to me directly from Japan, and said was bought new.

I guessed it was some refurbished one, as it was bought in 2013, and Ricoh said the SDM problem was gone in 2012, but mine copy did failed with two years of constant use.
07-27-2017, 12:06 PM   #9
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Stiffness in DA* 16-50

This stiffness in a part of the zoom range was also mentioned in the comparative review with the Sigma and Tamron offerings here:

DA* 16-50mm vs. Sigma and Tamron 17-50mm F2.8 Comparison Review - Design and Handling | PentaxForums.com Reviews

The reviewers noted that this may only be confined to their test copy (which it now seems it may not be), but otherwise seemed to like the "feel" of the zoom when used manually.
I just went through the up and down-pointed tests and have the same sense of a slight stiffening. I've had no problems using this lens, and am not sure it's an "issue", otherwise I would have expected forum members to be vocal about it.

I'm wondering if it's something to do with the variation in the weight distribution of the glass elements at different points in the zoom range, but it may also simply be the weather sealing. My Sigma 17-50 does not have the same resistance.
07-27-2017, 03:49 PM   #10
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Thanks for the help everyone. I contacted the seller and he assured me the lens was repaired in May and the stiffness is normal. Seeing the other comments here, makes me feel more confident in the lens. I think I just enjoy it like it is.

---------- Post added 07-27-17 at 05:51 PM ----------

QuoteOriginally posted by demondata Quote
This stiffness in a part of the zoom range was also mentioned in the comparative review with the Sigma and Tamron offerings here:

DA* 16-50mm vs. Sigma and Tamron 17-50mm F2.8 Comparison Review - Design and Handling | PentaxForums.com Reviews

The reviewers noted that this may only be confined to their test copy (which it now seems it may not be), but otherwise seemed to like the "feel" of the zoom when used manually.
I just went through the up and down-pointed tests and have the same sense of a slight stiffening. I've had no problems using this lens, and am not sure it's an "issue", otherwise I would have expected forum members to be vocal about it.

I'm wondering if it's something to do with the variation in the weight distribution of the glass elements at different points in the zoom range, but it may also simply be the weather sealing. My Sigma 17-50 does not have the same resistance.
I bet I have read this review about 30+ times before I finally purchased the 16-50. I never took note of this before. Thank you for brining this up. I also owned the Sigma a few years ago, and it didn't have this feel, so naturally I was worried. Thank you!

---------- Post added 07-27-17 at 05:52 PM ----------

QuoteOriginally posted by wtlwdwgn Quote
I received a brand new 16-50 from Pentax and it has the same stiffness.
That makes me feel much better, thank you !
07-27-2017, 06:56 PM   #11
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My copy bought new from B&H has always had a stiff spot around 28-35mm, and if you tilt it up or down, it will have more or less resistance based on whether you are zooming it in/out with the help of gravity or against. It almost feels like going over-cam in the zooming mechanism, and it's very consistent. It concerned me at first, but it has never changed it's action, and the lens is great and seems to work fine. I've taken many thousands of pictures with it.
07-29-2017, 07:56 AM   #12
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I had three copies of this lens and each of them exhibited the same behavior. The stiffness range differed slightly from copy to copy, but I do remember that it started around 28mm. Once something happened and the zoom ring no longer extended the barrel. In a minute or two, after some fiddling everything worked fine.
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