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04-26-2012, 07:49 PM   #1
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BF issues with newer firmware on K-x?

I'm not sure if it was the firmware update, but ever since I did, some of my AF lenses started back-focusing, particularly the kit lens and the DA35, here's a sample from a recent car show:

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DA35 2.4, ISO400, f2.8, 1/90s

I aimed for the jaw since there's a lot of contrast there generated by the stage lights. At first I thought it was just the DA35, but when I tried another shot with the kit-lens it also BF'd, in bright sunlight. Should I go to debug menu or send my camera for re-calibration, or any other step I should take?

04-26-2012, 08:40 PM   #2
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I am updated on fware on two Kx bodies and never had any BF|FF issues, I also shot with the 35 2.4 and never had any issues. I would do the ruler shoot method to test for BF|FF - also go into debug mode and do the adjustment then check again with the ruler test.
04-28-2012, 11:22 AM   #3
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Just because you aimed for the jaw doesn't mean the camera chose to focus there. The AF sensor is a pretty broad area. if you aimed at the jaw, the hair would be in range as well, and the camera would be justified in focusing there instead if it chose. Better to aim at an area at least as broad as the AF sensor.
04-29-2012, 05:39 PM   #4
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QuoteOriginally posted by Marc Sabatella Quote
Just because you aimed for the jaw doesn't mean the camera chose to focus there. The AF sensor is a pretty broad area. if you aimed at the jaw, the hair would be in range as well, and the camera would be justified in focusing there instead if it chose. Better to aim at an area at least as broad as the AF sensor.
That happened to me before when using auto-5 or auto-11 points, but I was using center-point only that time I took that certain photo (and the light was not so bad), so I'm pretty sure there should be enough for the AF sensor to lock on at the spot I aimed at.

04-30-2012, 02:55 PM   #5
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You might think so, but you'd be wrong. Do some testing by focusing on a black dot on a piece of white paper, seeing how far off-center you can get while still achieiving focus. You'll see it's pretty far. The hair would *definitely* have been in range had you focused on the jaw. Of course, the fact that the K-x doesn't superimpose the red dot so you can see where the center is all that well doesn't help.
05-01-2012, 02:54 AM   #6
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QuoteOriginally posted by Marc Sabatella Quote
Of course, the fact that the K-x doesn't superimpose the red dot so you can see where the center is all that well doesn't help.
True, that one. Especially in low light, it's hard to see where the actual center of the frame is, especially when the subject is moving. Will do some more tests in a while. Thanks!
05-01-2012, 03:03 AM   #7
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Did you have any AF adjustments turned on? These things might have gotten reset.
05-01-2012, 03:18 AM   #8
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QuoteOriginally posted by Na Horuk Quote
Did you have any AF adjustments turned on? These things might have gotten reset.
When I shot the photo above, none. I tried the debug menu method yesterday and it somehow worked, but when I disabled it today the problem went back, but to a lesser degree. I think I'll have to do additional tests, the BF problem seems rather frequent only under yellowish or multi-source lights.

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