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07-25-2011, 05:28 PM   #1
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Pentax F 35-70 lens help urgently needed

Hi, I'm a genuine newbie, so that's why I posted here rather than the lens section) with a Kx that I truly love, but I haven't been satisfied with the sharpness of many of my pictures. So I bought an SMC Pentax-F 35-70, 3.5-4.5 zoom lens off ebay because it got good reviews here on the forum, it was auto-focus, reviewers said it was fairly sharp, and I got it for reasonably cheap ($70). Well, it arrived today and I was excited to try it out, but now I don't know if I bought a bum lens or if there is something about the camera-lens connection that I don't understand.

For starters, I can't change the focal length at all. The focal length ring has no effect on anything. It turns, but nothing changes. I've got 4 other lenses and have never had this problem. Secondly, the thing has a terrible time finding focus. Even outside in daylight the lens just hunts and hunts and hunts. Sometimes it actually finds focus, but I've had more luck with it on manual. I know it can take sharp pictures because some of the manual shots I took were very sharp (for me, at least), and even some of the auto-focus pics were sharp. But usually the lens just hunts and hunts and never focuses.

So I need to know whether I got a bad lens or if there is some button or dial or menu item that I don't have set right. I can't imagine anybody selling a lens that actually has all of these problems. (Oh, and the aperture can only be set in camera with the ring set to A.)

Can anybody help? I don't know whether to send it back or what to do with it. I'd hate to send it back and have it be something I was doing wrong. Thanks, Jim

07-25-2011, 05:42 PM   #2
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I think I was bidding on that one!

Not sure about the focal length changing. That lens should have three 'rings' the front one is focus, the middle one is focal length and the back one is the aperture ring. When turning the focal length ring does the lens front move in and out? If it is not moving then I suspect you might have a problem. There is a macro setting on it though, are you in macro? But if it turns freely then probably not.

The aperture ring must be on 'A' for the camera to be able to control the aperture. Any other setting means you are setting the aperture manually on the lens, This is normal behavior.
07-25-2011, 06:10 PM   #3
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No, the focal length ring has no effect on anything until you get to macro. When I get to macro, the lens comes out. Until then, the lens does nothing. I just can't imagine anybody selling a lens that is so screwed up (if that's the case). I honestly don't know what to do.
07-25-2011, 06:13 PM   #4
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A few things that might help"
1) Set your camera to "allow use of aperture ring" on the custom settings menu. Now you don't HAVE to have it set to "A", although you probably will want to anyway.
2) Now the focus issue. This lens has a "macro mode" which is entered when the zoom ring is turned past 70mm. In that mode it will only focus closely, not at a distance. Hopefully you are in that mode. Try twisting the zoom ring to 70mm, and then to 50mm or 35mm. Hopefully it will now focus normally. If that doesn't do it, it may be broken and time for a return.

Fingers crossed! I like that lens a lot.

Oops! Just saw your preceding post. Sounds bad. But really, people will sell some amazing garbage on eBay. I got one lens literally falling apart despite being "like new!". You should be able to get your money back if it is not working correctly.

07-25-2011, 06:26 PM   #5
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I have this lens in front of me; when I turn the focal-length ring (marked with 35, 50, 70 and macro), the lens extends out either way you turn it. The least amount of protrusion of the lens is at the 70mm mark. So based on what you described, it is very likely that you have a faulty lens. Hope it helps...
07-25-2011, 06:29 PM   #6
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No, I've got the macro mode, just nothing else. One thing though, when I change the focal length ring, nothing happens, yet when I hit the info. button, it shows that I have changed focal lengths, even though the lens didn't move. So it would seem that the ring is giving info. to the camera, despite it not actually doing anything.
07-25-2011, 07:18 PM   #7
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Send it back. You can find another, that works.
07-25-2011, 07:37 PM   #8
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Just contacted the seller. I guess we'll see what happens.

07-25-2011, 08:17 PM   #9
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Too bad, returns are always a hassle. But it sounds as if the focal length ring is not moving the lens elements. On a simpler lens that might be a simple fix like tightening up some set screws. On a zoom like that I would not attempt to fix it.

Hope you can return it. Best of luck, and it might have been me!
07-26-2011, 04:50 AM   #10
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Looks like there's a fault on this lens... Shame as (my copy) it's deffo sharper than the kit 18-55...
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