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View Poll Results: Have you experienced FF/BF problems with your lenses?
No 1727.87%
Yes, but only in-body adjustments were necessary 3455.74%
Yes, one or more lenses had to be sent in 1016.39%
Voters: 61. You may not vote on this poll

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11-22-2011, 04:05 AM   #16
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QuoteOriginally posted by RonHendriks1966 Quote
I think that the people who say NO don't know how to measure.
While this is unlikely to be true for all who report "no", you probably have a point.

It also seems likely that one or the other adjustment is made based on incorrect measurements (e.g., by using rulers and other inappropriate setups). My AF adjustment hints contain some useful advice with respect to measuring the need for AF adjustments.

P.S.: Just in case a "no problem with Pentax lenses but Sigma/Tamron/... issues" mood develops. Clearly, the AF fine adjustment support on Pentax bodies is aimed at genuine Pentax lenses and no other. Food for thought.

11-22-2011, 04:16 AM   #17
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QuoteOriginally posted by hsp-2007 Quote
what does it mean back focus issue? like when you point to focus something and it seems to be on focus but in fact the real fine focus is some millimeters ahead?
Your example describes front focusing.
When a camera / lens combination back-focuses, the plane of focus is behind the intended focus target.

I wrote "camera / lens combination" because both components are involved in producing front / back focusing. Without access to testing equipment / software, it is not easy to identify the real culprit and I believe it is not unusual for both to contribute.

Ascertaining whether there is a real front focus or back focus issue as opposed to the camera just having a different idea on what to focus on than you have, requires a bit of effort. Contrary to common belief, the AF sensors in Pentax cameras are not AF points but rather large areas. So it is quite possible for the camera to pick another focus target within a selected area than the target you'd like it to focus on.

Only if there cannot be any doubt as to which plane the camera should be focusing on, one can start to measure front / back focusing.
11-22-2011, 06:31 AM   #18
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My 16-45 not only back focuses on my K10D, it also focuses past infinity. Not a good combination, with no AF adjustment available on the K10D. No, I haven't sent it in for adjustment. Hoping to upgrade to a K-5 ...
11-22-2011, 09:44 AM   #19
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QuoteOriginally posted by RonHendriks1966 Quote
I think that the people who say NO don't know how to messure. It is a relatively new thing for our camera's to adjust and I think that in a few years time non of us will find it strange to messure our lenses to adjust them to get critical sharpness.
Probably true but as I mentioned, I haven't had an issue with OOF shots that have given me a reason to. I know that some people get out lens charts first thing and check if the lens is alright. I use my backyard and the kitchen.


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