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02-28-2013, 12:02 PM   #1
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Backfocusing for the FA*300 f2.8 on K5 Ltd

I just bought the FA*300 mm f.2.8 and I`ve got a problem that I never had before. On all my lenses (FA and DA ) I have checked the focus , using the LV focus and compared it to *normal* AF , and adjusted the focus in the menu , accordingly. This has been ok for all my lenses, and been spot on for the lot. On this lens is doesnt seem to react to adjustments at all ! The lens back focuses a tad , and even on - 10 in the menu , it doesnt seem to react on this.

I have a K5 Limited , and also borrowed a K5IIs from a friend . The lens has the same problem on both houses.. (The IIs is better , not so nervous* in the focusing , and a little better in focus to start with. )
I have the newest firmware.
Anyone with suggestions ?

02-28-2013, 12:28 PM   #2
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QuoteOriginally posted by Mundus Quote
I just bought the FA*300 mm f.2.8 and I`ve got a problem that I never had before. On all my lenses (FA and DA ) I have checked the focus , using the LV focus and compared it to *normal* AF , and adjusted the focus in the menu , accordingly. This has been ok for all my lenses, and been spot on for the lot. On this lens is doesnt seem to react to adjustments at all ! The lens back focuses a tad , and even on - 10 in the menu , it doesnt seem to react on this.

I have a K5 Limited , and also borrowed a K5IIs from a friend . The lens has the same problem on both houses.. (The IIs is better , not so nervous* in the focusing , and a little better in focus to start with. )
I have the newest firmware.
Anyone with suggestions ?
Sounds like the lens may be in need of a calibration, should be quick and easy for the service center.
02-28-2013, 01:01 PM   #3
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QuoteOriginally posted by VisualDarkness Quote
Sounds like the lens may be in need of a calibration, should be quick and easy for the service center.
Thanks VD , here in Norway is just one service center and just one guy. Everybody with a Pentax knows his name I guess I have to send him a email about this .
02-28-2013, 01:03 PM - 1 Like   #4
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QuoteOriginally posted by Mundus Quote
Thanks VD , here in Norway is just one service center and just one guy. Everybody with a Pentax knows his name I guess I have to send him a email about this .
Only one center here in you neighbor Sweden too but more personnel, a nice service center though! I guess you will have to send your camera in too with the lens to get a perfect calibration.

02-28-2013, 02:57 PM   #5
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A backfocus problem would need a +ve correction, not a -ve correction.
02-28-2013, 05:17 PM   #6
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I kind of get confused by that back and front term The lens move the focusing ring to a greater distance , laying the focus area beyond the object .Excuse my english
02-28-2013, 05:30 PM   #7
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In Pentax terminology, front and back refers to the relative position of the actual focus point compared to the camera's internal idea of what the focus point is. If the actual focus point is farther away, then it is back focusing. This requires a positive correction to bring it in line. I believe other camera manufacturers reverse the reference points so it can be confusing.
02-28-2013, 06:59 PM   #8
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The one I had needed +20 on my k20d, but still wasn't sharp and not because of focus, just not sharp. Hopefully you have a good service center, pentax USA left me hanging.

03-01-2013, 04:13 AM   #9
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It seems like my FA 31 needs changing of fine-focus also. Earlier this beauty was spot on after I adjusted the fine-focus. Now its off. Hm... Pentax changed a lot to the autofocus system with the latest firmware, could it be a bug ?
03-01-2013, 04:23 AM - 1 Like   #10
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Sell me the lens !
03-04-2013, 01:34 PM   #11
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Hello, guys??? Did you ever consider that the camera is off and not the lens?
After readjustment of my K5 my lenses all fall on the negative copensation side from -5 to -11 (:-)) So my camera is still not centered around 0. Balme the camera or blame Pentax QC, but not the lens first.
03-08-2013, 09:09 AM   #12
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I found a solution , I debugged my K5 and moved *0* to +8. That gave me more room , enough to get the lens just acceptable in-focus at +10 . I had to adjust my other lenses after this of course.
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