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Old Aug 18, 2009, 12:57 PM   #1
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Default Focus Point Adjustment

Just got the Pentax 17-70 and started using it on my K20d. Objects 10-0 or closer seem to be fine-anything further than 10-0 are extremely soft. My old DS & DA 16-45 blows it away. I have never tried the focus point adjustment-any suggestions would be appreciated.
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Old Aug 18, 2009, 3:09 PM   #2
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Before you start adjusting focus points, make sure that the lens isn't defective or something like that. Try focusing manually and see if you can get a sharp picture at the longer distances - i.e., brick walls, which will also check for signs of decentering. If you can get aharp photo, then you can start shooting focus charts to find out exactly what the problem is (back or front focus).
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Old Aug 18, 2009, 8:18 PM   #3
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Before you start adjusting focus points, make sure that the lens isn't defective or something like that. Try focusing manually and see if you can get a sharp picture at the longer distances - i.e., brick walls, which will also check for signs of decentering. If you can get aharp photo, then you can start shooting focus charts to find out exactly what the problem is (back or front focus).
Thanks-will start with the brick walls. Appreciate the info
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Old Aug 18, 2009, 11:37 PM   #4
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Let us know what you find out, whether the lens is defective or whether you have a front/back focus problem.

The funny thing is that I have an old DA*50-135 and with real-world shooting and my previous cameras, it's had a tendency to backfocus a bit (it's close enough with the K20 that I never bothered shooting charts etc.). It seemed to be a bit off with the K-7, but when I shot focus charts, they indicated a possible front focus. At that point I put the charts away and figure I'll try it again some other time. In any case, it's never been that far off.

Good luck with yours.
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Old Aug 19, 2009, 8:02 AM   #5
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Took these last nite. Shot on the left is with the DA 17-70. Shot on the right is with my DA 40 2.8. All using the K20d, onboard flash-all other settings identical. Anyone think the focus adjustment will work? Or should I send it to Pentax for an estimate.
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Old Aug 19, 2009, 10:47 AM   #6
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There's nothing sharp in that picture. Where is the camera focusing? It's hard to say from this example, but it doesn't look like front or back focus is the problem. It's also difficult to tell from this picture whether you have a problem with decentering, but it might (looks a little blurrier on the top than on the bottom, but at such a reduced size it's hard to tell). Focus adjustment would help if you focused on the front flower and it were OOF with the brick wall sharp (back focus) or you focused on the brick and the flowers were sharp while the wall wasn't (front focus). In your case, there's nothing sharp so I would say your lens is broken. Can you get a sharp picture by manually focusing the lens? If so, then your problem is probably the AF/SDM mechanism. If you can't, then the optics are somehow messed up. My guess is that there's an optic problem not a focus problem and you should send the lens in for repair/replacement, but I can't really say one way or the other from just this photo.

If you are interested, here's a link to an album with some of my DA 55-300 pictures, starting with the brick wall series I shot with my defective lens. You can download the original full sized files if you want, to see if what you are seeing with your lens is similar (this is what I was talking about when I suggested shooting brick walls - you can clearly see that one side of the frame is significantly blurrier than the other, and the picture isn't all that sharp, even in the center). http://mtngal.zenfolio.com/p691012471/e13ac371d - that can give you an idea of what I was looking for. I'd still like to know if you can get a sharp picture with manually focusing your lens.
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Old Aug 19, 2009, 11:39 AM   #7
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There's nothing sharp in that picture. Where is the camera focusing? It's hard to say from this example, but it doesn't look like front or back focus is the problem. It's also difficult to tell from this picture whether you have a problem with decentering, but it might (looks a little blurrier on the top than on the bottom, but at such a reduced size it's hard to tell). Focus adjustment would help if you focused on the front flower and it were OOF with the brick wall sharp (back focus) or you focused on the brick and the flowers were sharp while the wall wasn't (front focus). In your case, there's nothing sharp so I would say your lens is broken. Can you get a sharp picture by manually focusing the lens? If so, then your problem is probably the AF/SDM mechanism. If you can't, then the optics are somehow messed up. My guess is that there's an optic problem not a focus problem and you should send the lens in for repair/replacement, but I can't really say one way or the other from just this photo.

If you are interested, here's a link to an album with some of my DA 55-300 pictures, starting with the brick wall series I shot with my defective lens. You can download the original full sized files if you want, to see if what you are seeing with your lens is similar (this is what I was talking about when I suggested shooting brick walls - you can clearly see that one side of the frame is significantly blurrier than the other, and the picture isn't all that sharp, even in the center). http://mtngal.zenfolio.com/p691012471/e13ac371d - that can give you an idea of what I was looking for. I'd still like to know if you can get a sharp picture with manually focusing your lens.
Thanks for your reply-the shots were taken about 8-0 from the flowers using spot focus. What's is strange is that the camera is giving the "in focus" beep & sign in the viewfinder. Manual focus does not change anything. Probably going to send to Pentax for an estimate
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Old Aug 19, 2009, 12:13 PM   #8
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Thanks for your reply-the shots were taken about 8-0 from the flowers using spot focus. What's is strange is that the camera is giving the "in focus" beep & sign in the viewfinder. Manual focus does not change anything. Probably going to send to Pentax for an estimate
This is my only SDM lens-anything I am missing with this type of lens? if I take a shot about 4-0 or less everything is in perfect focus. Any other ideas?
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Old Aug 19, 2009, 3:51 PM   #9
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It could be something to do with the focus gears, sort-of what Jason had with his defective DA*16-50. But if you can't get a sharp picture using manual focus (ignoring the beep and sign) by itself, it's not necessarily the SDM mechanism. It's definitely NOT something that focus adjustment will fix. In any case, optics or focus, it sounds like Pentax needs to fix, I'm out of ideas. Well, a basic idea which I assume you've already tried - you did clean the contacts on both camera and lens, didn't you (I ask because most of my problems are dumb things like this that I don't think about).
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Old Aug 19, 2009, 5:29 PM   #10
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It could be something to do with the focus gears, sort-of what Jason had with his defective DA*16-50. But if you can't get a sharp picture using manual focus (ignoring the beep and sign) by itself, it's not necessarily the SDM mechanism. It's definitely NOT something that focus adjustment will fix. In any case, optics or focus, it sounds like Pentax needs to fix, I'm out of ideas. Well, a basic idea which I assume you've already tried - you did clean the contacts on both camera and lens, didn't you (I ask because most of my problems are dumb things like this that I don't think about).
No-I didn't try that-what do you use? It would be nice if that was the cure.
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