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12-17-2011, 05:52 PM   #1
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Backfocus with Pentax 18-250mm on k100d

hi

i just bought a brand new pentax 18-250mm and im really not impressed with the autofocus, i read very good reviews of the lens so i'm assuming there's something wrong. I'm getting terrible backfocus and subjects are blurred, does updating the firmware might help?

thanks!!

12-17-2011, 06:56 PM   #2
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Since that lens has been discontinued for a while I am impressed you found a new one. Care to share your source? I am looking for one.

I do not have a K100d but I do not recall seeing any mention of a firmware update that improved focus on that camera. Are you doing controlled tests (tripod, fixed well lit target)? If so and you cannot get good results maybe you got a bad copy of the lens, from all reports it is quite good considering the zoom range.

Not sure if the K100d has a fine focus adjustment, maybe someone else will chip in with that info.
12-17-2011, 07:26 PM   #3
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Please post pictures that demonstrate the problem - preferably a controlled focus test performed after carefully reading the instructions. Most of the time, people erroneously think they are seeing backfocus when really it's simple matter of the camera choosing to focus somewhere other than where you intended.
12-17-2011, 08:53 PM   #4
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I really like mine on the K200D, but it took awhile for me to get used to its limitations. I never use it now without a tripod, and in anything but bright sunlight it often struggles to focus. At twilight, or indoors, the focus is really iffy. And, around 200 it starts to go soft. At 250, it is quite soft, tripod or not. Quite good for flowers at the long end, if you like soft focus, but not so hot for landscapes.

12-18-2011, 02:57 PM   #5
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Hi, tanks for your feedback, I'm posting two photos, on both I used manual AF point and i am dead sure I did not focus on the background :S
i cannot get it to auto focus decently, I'm actually thinking of taking back to the store and replacing it with a sigma 18-250mm

any thoughts

http://www.marioborg.com/tests/IMGP9545.JPG
1/60s f/4.5 ISO200 at 43mm

http://www.marioborg.com/tests/IMGP9939.JPG
1/20s f/4.5 ISO200 at 18mm
12-18-2011, 06:29 PM   #6
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You might have a bad copy. Mine has treated me well even wide open. I do use center focus a lot though.

250mm F6.3


250mm F8.0


142mm F6.3

Last edited by john5100; 12-18-2011 at 06:54 PM.
12-18-2011, 06:36 PM   #7
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QuoteOriginally posted by Marc Sabatella Quote
Please post pictures that demonstrate the problem - preferably a controlled focus test performed after carefully reading the instructions. Most of the time, people erroneously think they are seeing backfocus when really it's simple matter of the camera choosing to focus somewhere other than where you intended.
x2. Are you sure you know where your focusing? I dont' mean to be rude, but it seems otherwise. I don't have this lens but it looks pretty crisp, as far as what's in focus. . . .
12-19-2011, 03:33 AM   #8
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Well done!! Show us the improvements.

12-20-2011, 05:20 PM   #9
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Hi, sorry for hopping on your thread, but please tell me about the firmware upgrade as I'm sure my firmware is not current in my K100D.

Vince
12-20-2011, 07:30 PM   #10
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QuoteOriginally posted by pako80 Quote
I think it was the last one because It was not showing in their stock and they suggested it
Sometimes you just get lucky. Good for you that you had the sense to jump on it when you saw it.
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