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07-10-2007, 05:43 PM   #1
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Front/Back Focusing Problem?

I have a K100D that is about three months old now. I did a focust test on my K100D with 40mm Limited using the info on the web (Home) to find that I might have a front focusing problem. I'm wondering whether this problem is caused by camera body or lens, how serious it can be, and how it can be fixed (if it needs to be fixed). I haven't noticed a serious focusing problem yet (though I'm not even sure what it should look like), but now it starts annoying me.

07-10-2007, 09:40 PM   #2
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QuoteOriginally posted by leex0187 Quote
I have a K100D that is about three months old now. I did a focust test on my K100D with 40mm Limited using the info on the web (Home) to find that I might have a front focusing problem. I'm wondering whether this problem is caused by camera body or lens, how serious it can be, and how it can be fixed (if it needs to be fixed). I haven't noticed a serious focusing problem yet (though I'm not even sure what it should look like), but now it starts annoying me.
The problem is caused by too many hours of internet surfing, a failure to think for oneself in a logical manner and not enough time spent making photographs.

Two tips:

1) Go shoot some photographs;

2) do it now!


FF/BF issues are not withing the users purview to determine or correct--that test you cite is pure poppycock in soooo many ways.
07-10-2007, 10:30 PM   #3
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QuoteOriginally posted by leex0187 Quote
I have a K100D that is about three months old now. I did a focust test on my K100D with 40mm Limited using the info on the web (Home) to find that I might have a front focusing problem. I'm wondering whether this problem is caused by camera body or lens, how serious it can be, and how it can be fixed (if it needs to be fixed). I haven't noticed a serious focusing problem yet (though I'm not even sure what it should look like), but now it starts annoying me.
If many of your real-life photos are out of focus and you have eliminated user error - that is, you understand how to use and focus the camera in a variety of situations - then maybe you have a focus problem.

However you state:

1. That after running this test you "find that I might have a front focusing problem"

2. "I haven't noticed a serious focusing problem yet"

3. "(though I'm not even sure what it should look like)"

It seems to me that what is annoying you is that you do not have a problem with focusing.

If you look hard enough for problems you will find them! As John said "Go shoot some photographs" but preferably not of test cards...

Good luck
07-10-2007, 11:17 PM   #4
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QuoteOriginally posted by leex0187 Quote
I have a K100D that is about three months old now. I did a focust test on my K100D with 40mm Limited using the info on the web (Home) to find that I might have a front focusing problem. I'm wondering whether this problem is caused by camera body or lens, how serious it can be, and how it can be fixed (if it needs to be fixed). I haven't noticed a serious focusing problem yet (though I'm not even sure what it should look like), but now it starts annoying me.
To do more accurate testing, don't shoot the chart at 45 deg. Shoot an object with good contrast and vertical and/or horizontal patterns at a plane perpendicular to the optical axis of the lens of the camera. Wide open the lens and take the shoot. If there is any mis-focusing, you will easily see it in the taken pictures. Here is an example:- Pentax *ist DS AF Dependency on Kelvin & Exposure Value

If you want to adjust the amount of FF or BF offset for your K100D, you may try this (but should be with great care and try at your own risk! :-)):-

RiceHigh's Pentax Blog: Screen Captures of the Secret Mode of the K100D

Do note that the offset adjustment and input of offset parameter is only applicable for *one* lens *either* under daylight or tungsten light. So, you should be aware that when you have fine tuned for one lens with accurate AF, the other lenses you have may yield even more inaccurate results on the same body after the adjustment. So, you will need to check with a few lenses of yours which you use more frequently and are unsatisfied with the accuracy and try to find an optimal value for the offset. Anyway, some users remember the setting for each lens under each lighting condition (daylight or yellow light) and enter the offset by entering the service mode each time they changed the lens (there were a few long threads at DPR and people told that they were doing and would do so).

Hope this helps.

07-11-2007, 01:59 PM   #5
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Thanks a lot for the replies! I agree I should spend more time shooting than surfing the web. Anyway, I'm too scared to adjust offsets myself as RiceHigh suggested. (thanks thou) I think I'll just forget about it for the peace of mind...
07-11-2007, 07:26 PM   #6
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Pardon my ignorance, but do FF/BF problems occur in manual focus mode as well?
Thanks.
07-11-2007, 08:37 PM   #7
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QuoteOriginally posted by Kguru Quote
Pardon my ignorance, but do FF/BF problems occur in manual focus mode as well?
Thanks.
Not an ignorance but good question, I think. The answer to your question is Yes, see:-

RiceHigh's Pentax Blog: When the Focusing Screen Lies (for Focusing and Metering)
07-11-2007, 08:52 PM   #8
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QuoteOriginally posted by jfdavis58 Quote
The problem is caused by too many hours of internet surfing, a failure to think for oneself in a logical manner and not enough time spent making photographs.

Two tips:

1) Go shoot some photographs;

2) do it now!


FF/BF issues are not withing the users purview to determine or correct--that test you cite is pure poppycock in soooo many ways.
That's the best answer that I've read anywhere yet, and we should all listen to it.

That being said, if I'm not heard from much the rest of this month don't worry, I'm just out taking pictures or at a short writing course I've signed up for

07-11-2007, 08:59 PM   #9
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QuoteOriginally posted by Kguru Quote
Pardon my ignorance, but do FF/BF problems occur in manual focus mode as well?
Thanks.
Do you take your eyeballs in and out with any regularity? If you do, then there is certainly room for mis-adjustment.

Yes, I'm yanking your chain, making a joke at your expense! I can be so rude like that!

I have FF/BF issues with a camera, only after too much scotch. And after too much RiceHigh!
07-12-2007, 08:50 AM   #10
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QuoteOriginally posted by jfdavis58 Quote
I have FF/BF issues with a camera, only after too much scotch. And after too much RiceHigh!
Oh, then you need to visit -

RiceHigh's Pentax Blog: Focusing for the scotch impaired
07-12-2007, 05:34 PM   #11
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You get your rice 'high' from excessive consumption of Saki and the like
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