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10-30-2011, 06:25 PM   #1
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FA31 Manual focus noise after first AF use with K-5

Just got a new K-5 (second one in three days, but that's another story) and just now I was playing with the FA31 Ltd. Wasn't shooting anything (I'm stuck at home and I don't feel like taking pics of my dirty laundry or whatnot) -- just running the AF. (It seems faster than on my K-7, but I usually use the FA31 in manual only.) It seemed to show the usual uncertainties of focusing in tungsten, but I wasn't trying to test anything. After just a few minutes of this, I put the lens back in manual, and suddenly found a strange noise had developed when I turn the focusing ring. It's a little ratcheting or sawing noise, hard to describe. It's louder when I focus toward infinity, a little softer turning the other way, and if I turn very, very slowly, I don't hear it all.

The lens is less than a year old, not heavily used, never had any problems with it. I'm sure there'll be no effect on actual use, but the timing is puzzling. Could the K-5 have thrown something out of whack -- and after just a few minutes of AF? -- in this lens?

Any insights much appreciated.

(oh, the lens is Made in Vietnam, if anyone cares. That's never worried me.)

10-30-2011, 07:31 PM   #2
hcc
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Could it be that the AF screw drive of the camera body is not properly disconnected from the lens?

When you set the camera to MF, the screwdrive should disengage itself from the lens mechanism to allow you to MF without damaging the motor. (That is, for the lenses whcih are not equipped with Quickshift).

Hope that the comment may help.
10-30-2011, 07:46 PM   #3
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Thanks hcc. That may be it, although I'm not feeling any extra resistance -- the lens turns as easily as before, but with that strange noise. I just hope this doesn't mean that I am damaging the motor every time I turn the ring. (I've always assumed this was a potential vulnerability, and I'm always careful to leave the camera in manual when I have the FA31 on it, when I'm carrying it in a bag, for fear of putting any pressure on the focusing mechanism.)

Love the lens; I hope this isn't a sign of major problems to come. And I hope the fault isn't somehow with the design of the K-5; could it just be running the screwdrive faster than older lens designs can handle?
10-31-2011, 12:40 AM   #4
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Does it happen as well when the lens is not mounted the body? Does it happen when you put the lens back on the K7 (if you still have it)?

10-31-2011, 01:44 AM   #5
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There is really nothing to break for this lens, maybe some screws were loose? Check infinity focus. If it shifts, some screws are loose. But this lens is never quiet due to the way it was built.
10-31-2011, 03:33 AM   #6
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QuoteOriginally posted by sterretje Quote
Does it happen as well when the lens is not mounted the body? Does it happen when you put the lens back on the K7 (if you still have it)?
Yes. to both. This is simply the sound the lens makes when turning the focusing ring by hand. It's not a squeak or anything either; it's a very regular, steady mechanical noise. Louder in one direction than the other, as I noted.

QuoteOriginally posted by wlachan Quote
There is really nothing to break for this lens,
I wish that were true
I know I didn't cause any damage to it by hand; I'm always careful to avoid even touching the focusing ring when the camera is in auto. If I were to hand the camera, with any non-quick shift AF lens on it, to anyone else to take a picture, I would switch the camera back to manual.

QuoteOriginally posted by wlachan Quote
But this lens is never quiet due to the way it was built
I'm not sure what you mean. If you're referring to the screw drive, remember that I'm talking about a sound made when manually turning the lens. It was perfectly quiet before, like all my lenses, when used manually.

QuoteOriginally posted by wlachan Quote
Check infinity focus.
I'll do that later today.

Thanks to both of you. If you think of anything else, let me know. I'm stumped.

Last edited by pentup; 10-31-2011 at 03:42 AM.
10-31-2011, 04:13 AM   #7
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QuoteOriginally posted by pentup Quote
I'm not sure what you mean. If you're referring to the screw drive, remember that I'm talking about a sound made when manually turning the lens. It was perfectly quiet before, like all my lenses, when used manually.
I know what you mean, and manual focus is not totally quiet with this lens, not according to my experience with 6-7 samples. The noise level can vary quite a lot thanks to the lousy QC, but I have not come across a sample that's totally quiet (maybe they do exist who knows). The noise is actually coming from the major barrels rubbing each other. The better mated ones will be quieter, some can be quite obvious. Still, there is nothing to break other than loose screws due to insufficient threadlock (another lousy QC) which is not that rare. But it is hard to figure out what went wrong w/o handling the lens personally, not by me anyway.
10-31-2011, 04:45 AM   #8
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QuoteOriginally posted by wlachan Quote
Still, there is nothing to break other than loose screws due to insufficient threadlock (another lousy QC) which is not that rare. But it is hard to figure out what went wrong w/o handling the lens personally, not by me anyway.
Thanks for the clarification; I see what you mean now. It could, I suppose, be pure coincidence that the noise developed immediately after using it on the K-5 for the first time. Bad timing!
Damn, that's a crushingly expensive lens that's always touted for its "build quality."
Well, as long as it doesn't get worse and doesn't interfere with picture taking...
Thanks for your help.

11-01-2011, 07:56 AM   #9
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I have seen a copy of this lens that had similar noise at infinity. But the noise was gone after AF, which is diferent from yours. If I took it off camera and manual focused it, eventually the noise came back. And I noticed if I turned the lens 90 degree along its axis (as if it's at veritical shooting position), it didn't have the noise.

I tend to agree with what wlachan said.
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