[DavidSKAF3]

This morning the used 16-45 f/4 I received a week ago from eBay for $159 would not autofocus. I became very frustrated. It looks great, and the seller has a 100 percent positive feedback score, and he advertised it as working just fine.


After I determined that it was the lens that was not working, and not the camera, I tried another lens. And it autofocused just fine. Then I took the lens off the K-5 and gave it a closer inspection. I discovered that the 16-45's manual focus ring would not turn! It would not move at all. Completely stuck. Like it was locked. And there wasn't any sort of lock switch I could find, and I so I re-mounted the lens and moved the AF selector to both AF and MF positions. But the focus ring just would not turn. Furthermore, there also was a strange "bump" of sorts when I rotated the zoom ring, that I could not recall being there or not! I thought the bump might have been some sort of normal lens creep deterrent. Or not. Maybe?


But the 16-45 was definitely not working right, and I was furious! I was so mad that eventually I angrily yanked on the focus ring out of frustration (not while it was mounted to the camera!), and suddenly it came loose!


So I made sure both rings were completely loose again, and re-mounted the lens. Now the 16-45 seems to be working just fine again, in AF and MF modes. So go figure!


But I'm worried if this incident could have hurt my new K-5, and what caused this lens to malfunction. I'm wondering if I bought a bum lens. And if I should expect it to get "stuck" again. I also started wondering about the K-5's AF assist beam, because I was indoors, and I didn't see it. Does the K-5 have one? I didn't see an option for it in the menus. And I think yesterday I inadvertently removed the SD card while the camera was on. Could that have affected the 16-45?


The 16-45 has its own AF motor inside it, right? Trying to use it while it was jammed couldn't have hurt the K-5's internal focusing motor, could it? Is there any way that a used lens could hurt my brand new camera? Should I avoid used lenses to be safe?

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Last edited by DavidSKAF3; 12-14-2013 at 01:48 PM.

[Na Horuk]

I think pretty much all modern Pentax DSLRs have an AF assist beam, but a) it needs to be enabled in the menu and b) it will still show up pretty rarely (and c) make sure your finger is not covering it ).
AF tests should be done in good light, daylight, not indoors. Tungsten and LED lights can confuse the AF, and the lack of light can make it impossible to lock focus.
But if the focus ring was stuck that indicates that there is another problem - the lens, not the camera. Can you inspect the focus ring and make sure its circular and not squished/damaged? It could be that during shipping the lens got squished or rattled.
When you take a photo, does the photo look equally sharp on all sides? Or is perhaps one half of the picture significantly blurrier?

If I were you I would do the following:
a) inspect the mechanics to the best of my abilities. See if the focus ring works consistently or if there is a resistance at any point. Same for zoom ring. Check if aperture blades work normally. Make sure the mount is not damaged. Inspect the lens barrel for any cracks or abnormalities.
b) Make sure the optics are consistent and produce good images at any zoom, aperture and focus setting. If this works well, a repair might be worth it. But if you need repair, still ask the seller to pay for it (as in, give you a "retroactive discount" or activate the shipping insurance). The photo must also be consistent - all corners should have similar quality, center should be even better than corners.
c) notify the seller of what is happening. Do this calmly, list the problems in a clear fashion, and ask what they think - and whether they have some return policy. Do this as soon as possible if you havent already. Do not accuse the seller of anything, merely ask for an explanation and help. They probably want this issue resolved, too.
d) the SD card should in no way affect the AF functions of the camera. The 16-45mm, as far as I know, does NOT have its own focus motor - it relies on the camera's motor. Make sure the AF screw (and other contacts on the mount) are clean and free of particles or grime. Just take a look and maybe wipe gently or use a rocket blower. But if it works with other lenses, then it should be fine.

Can the lens damage the camera's AF engine? Probably not, but I can't guarantee anything. I would not try to use the camera's AF with a lens that has a stuck/damaged focus mechanism. Maybe the camera is smart enough to know when to stop pushing the AF, but I wouldn't bet on it. It seems too risky to damage a fine K-5 camera body just because one lens is behaving oddly.

Oh, and one more thing. The 16-45mm has an outer and an inner barrel. It extends when you zoom, so make sure that the inner barrel is not bent, too..

[stormtech]

You said you used the lens this morning - is this the first time you used it since receiving it a week ago?

The 16-45 lens is screw drive - the focusing is accomplished by the focus motor inside your K-5.

Forcing the focus or zoom ring is never a good idea. When the lens is mounted on your K-5, it is in fact connected to the focus drive inside the camera.

While the ebay feedback is important, of more importance is the sellers return policy. Did they have the 14 day return option or not?

[stevebrot]

The 16-45 has its own AF motor inside it, right? Trying to use it while it was jammed couldn't have hurt the K-5's internal focusing motor, could it? Is there any way that a used lens could hurt my brand new camera? Should I avoid used lenses to be safe?

No, the 16-45 does not have its own motor and as noted above, unless a lens has quick-shift, it is never good to manually focus with the AF engaged.

I would return the lens with a full explanation.


Steve

[DavidSKAF3]

You said you used the lens this morning - is this the first time you used it since receiving it a week ago?

Thanks to all for your quick and informed responses! I used it yesterday without any problem.

[DavidSKAF3]

I just took these photos with the K-5 & 16-45 a few minutes ago outside my apartment. The rings are both moving freely at the moment. These pictures look to be in focus all around. But I leave it to you guys for advice on how to proceed. I would like it if this incident was just a "hiccup" and not have to go through all the bickering and hassles and explaining of making a return. I like the darn lens too! Darn it!


Furthermore, I think I may have figured out a possible cause? I have been keeping the camera in the form fitting neoprene case in the last photo below. It fits the 18-55WR comfortably, but I have to admit the 16-45 is pretty snug in there with its hood. Maybe too snug? And I like this neoprene case a lot. But anyway, to be safe, I switched cases. The camera is in much looser case now.

[interested_observer]

I have had my 16-45 for about 7+ years now. I bought it new and as with all of my equipment have taken care of it. About 2 years ago, it suddenly started acting up (not focusing as in the past it was dead on), so I took it down to CRIS to see what the problem was. It turned out to be the focusing gears. I am going off of memory now, but as I remember it they are worn - normal wear and tear. My intent was to send it off to Eric for the replacement of the gears, but the lens is still sitting on my shelf. Something that I need to get done. I have been really using primes the last 3 or so years, thus it has not been a real pressing problem.

Your problem sounds very similar to mine.

[DavidSKAF3]

I have had my 16-45 for about 7+ years now. I bought it new and as with all of my equipment have taken care of it. About 2 years ago, it suddenly started acting up (not focusing as in the past it was dead on), so I took it down to CRIS to see what the problem was. It turned out to be the focusing gears. I am going off of memory now, but as I remember it they are worn - normal wear and tear. My intent was to send it off to Eric for the replacement of the gears, but the lens is still sitting on my shelf. Something that I need to get done. I have been really using primes the last 3 or so years, thus it has not been a real pressing problem.

Your problem sounds very similar to mine.

Thank you for your reply. Did your focus ring get stuck, like immovable?

[DavidSKAF3]

Just went back to eBay to check the return policy.


It was a private seller. His policy is no returns or exchanges, but the item is covered by eBay's "Money Back Guarantee."


Hmm. It does seem to be working now. I wonder if the tight neoprene case pinched it too hard?

[interested_observer]

Thank you for your reply. Did your focus ring get stuck, like immovable?

No, not that I remember. However, gears can fail in a number of ways, some of which will just slip (never achieving accurate focus) or jam. However, when it jams something is caught up on something - preventing the necessary movement, so it a very good chance that its associated with the gears, or focusing mechanism that the gears drive.

I have read very few lens failures such as mine, non SDM, etc. For the most part the screw drive AF is pretty trouble free.

[DavidSKAF3]

No, the 16-45 does not have its own motor and as noted above, unless a lens has quick-shift, it is never good to manually focus with the AF engaged.

I would return the lens with a full explanation.


Steve

What is Quick Shift?


Thx

[DavidSKAF3]

No, not that I remember. However, gears can fail in a number of ways, some of which will just slip (never achieving accurate focus) or jam. However, when it jams something is caught up on something - preventing the necessary movement, so it a very good chance that its associated with the gears, or focusing mechanism that the gears drive.

I have read very few lens failures such as mine, non SDM, etc. For the most part the screw drive AF is pretty trouble free.

Are these gears in the lens or the camera? Sorry about all these dumb questions!

[DavidSKAF3]

I have had my 16-45 for about 7+ years now. I bought it new and as with all of my equipment have taken care of it. About 2 years ago, it suddenly started acting up (not focusing as in the past it was dead on), so I took it down to CRIS to see what the problem was. It turned out to be the focusing gears. I am going off of memory now, but as I remember it they are worn - normal wear and tear. My intent was to send it off to Eric for the replacement of the gears, but the lens is still sitting on my shelf. Something that I need to get done. I have been really using primes the last 3 or so years, thus it has not been a real pressing problem.

Your problem sounds very similar to mine.

BTW So what is CRIS and who is Eric?


Thx

[interested_observer]

The screwdrive motor is in the body of the camera and turns a screw head in the mounting ring of the lens mount on the body.

The lens has a mechanical coupling that engages with the mount coupling so that the body screwdrive AF motor turn a shaft in the lens body that mechanically drives a set of gears that moves the lens internal assembly in and out. Here is some additional information....

• https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/63745-screw...us-inside.html

Inside the lens body, there are also guides that slide within a set of channels so that when the body's screwdrive motor turns the shaft that turns the gears the internal body assemblies will slide smoothly and not bind.

hope that helps...

[grahame]

I will suggest return the lens if possible.
If for nay reason, returning is not a solution, sending the lens to CRIS or Eric is the right way to go.
CRIS is pentax authorized camera/lens repair store in US. you can google and find their website. YOu can create an account and request a repair quote online, so you can check your status in the future easier. Or you can just mail the lens to them and they will contact you with the problen they find and the price for repair. They could be slow, but charge is reasonable.
Eric is a very nice guy worked for pentax for many years and he knows very well about pentax gears. HIs repair price is usually a little lower than CRIS. Again, google eric and pentax you will find him.
Good luck with you lens repair. 16-45 is a great lens