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Old Aug 19, 2009, 5:59 PM   #11
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A clean microfiber cloth if there's no sign of grease or anything. I've always been a little afraid to use alcohol, in case I got a bit where it shouldn't (especially on the camera). I've never felt the need for more, just the microfiber cloth seems to do well enough for what I've needed.
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Old Aug 19, 2009, 8:35 PM   #12
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A clean microfiber cloth if there's no sign of grease or anything. I've always been a little afraid to use alcohol, in case I got a bit where it shouldn't (especially on the camera). I've never felt the need for more, just the microfiber cloth seems to do well enough for what I've needed.
Thanks-that will be the next step.
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Old Aug 19, 2009, 11:19 PM   #13
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I recommend trying a focus chart if you're considering using the focus point adjustment. Set the aperture at its widest to minimize DoF, position the camera at a 45 degree angle to the sheet of paper, set the camera at center point, and have AF focus on the line on the center of the chart.

If the area below the line is sharp, move the AF adjust more to the negative. If the area above the line is sharp, move the AF adjust more to the positive. Hopefully you can get the focal plane to contain the line. If not, your lens might have a problem.

See this link for more details and focus charts with grids of varying opacity (I recommend the 10% version): http://regex.info/blog/photo-tech/focus-chart

- Jason
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Old Aug 21, 2009, 12:20 AM   #14
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I recommend trying a focus chart if you're considering using the focus point adjustment. Set the aperture at its widest to minimize DoF, position the camera at a 45 degree angle to the sheet of paper, set the camera at center point, and have AF focus on the line on the center of the chart.

If the area below the line is sharp, move the AF adjust more to the negative. If the area above the line is sharp, move the AF adjust more to the positive. Hopefully you can get the focal plane to contain the line. If not, your lens might have a problem.

See this link for more details and focus charts with grids of varying opacity (I recommend the 10% version): http://regex.info/blog/photo-tech/focus-chart

- Jason
Finally had a few minutes to use this lens. Appears to be a back focus problem. Right now it is at -2 and seems to be reasonable. Considering how much this lens cost it is a real "onion" This is the only SDM lens I own-all my other DA lenses blow this one away. Why would Pentax add the focus adjustment feature to the K20d unless they anticipated focusing problems. As far as I know none of their previous DSLR's had this option. Looks like this will be my only SDM lens. I have a wedding to shoot on 9-12-09 and both the K20d & this lens will stay at home-all my weddings over the past three years have been shot with my Ist DS & K10d and all my brides have been happy. I need a confidence level of 150% on wedding days and right now that is 0 for the 17-70.

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Old Aug 21, 2009, 10:57 AM   #15
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My DA*50-135 backfocused on my K10 and it was frustrating that I couldn't adjust it. It focused all right with the K20 (the little backfocusing it did wasn't enough for me to actually do anything about it). I suspect it might be backfocusing a bit with the K-7 but have been getting inconsistent results so am not sure. I have 2 other SDM lenses that are perfect with the K-7 (haven't tried them with the K20). I can certainly understand your not trusting the 17-70 at this point.

Were you ever able to get a sharp picture focusing manually?
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Old Aug 21, 2009, 1:49 PM   #16
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My DA*50-135 backfocused on my K10 and it was frustrating that I couldn't adjust it. It focused all right with the K20 (the little backfocusing it did wasn't enough for me to actually do anything about it). I suspect it might be backfocusing a bit with the K-7 but have been getting inconsistent results so am not sure. I have 2 other SDM lenses that are perfect with the K-7 (haven't tried them with the K20). I can certainly understand your not trusting the 17-70 at this point.

Were you ever able to get a sharp picture focusing manually?
Not really-the bizarre thing is that it focuses quickly and in the viewfinder it looks great-look at it on the screen and it is junk. I've tried (3) different monitors so it's not that. Really didn't want a $480 paperweight.
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Old Aug 21, 2009, 1:53 PM   #17
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Have you updated your K20 firmware?
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Old Aug 21, 2009, 5:35 PM   #18
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Have you updated your K20 firmware?
It's version 1.03
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Old Aug 24, 2009, 11:48 AM   #19
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It's version 1.03
Thanks for everyone's input-I think I got a real piece of junk-my old kit lens puts this to shame-no more SDM lenses for me.
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Old Aug 24, 2009, 3:04 PM   #20
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The fact that you can't MANUALLY focus it and get something sharp makes me question whether the problem is the SDM/AF mechanism at all - it may be, but then it may not be. My first copy of the DA 55-300, a non-SDM lens, was a piece of junk, too. It wasn't sharp at all until about f16 or so. It focused all right, but the lens had bad optics.

On the other hand, I now have 3 outstanding lenses that are SDM. We'll see today if the replacement DA*16-50 is any better than the first one I returned.
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