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01-16-2009, 11:32 AM   #1
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Focusing Issues with the K10d

My K10d seems to 'backfocus' despite me changing the settings in the debug mode. I currently have the camera set to +270um, and this is still the result I get. I focused on the '2GB' logo and waited for the red confirm square to beep.

Pentax-M 50mm 1.7 @ 2.8:




Same results with all my lenses (Takumar 55 1.8, Pentax-M 50mm 1.7, D-Xenon 18-55 AF, Tak 135mm, etc...) . My old DS2 nailed the focus with the same lenses.

Any suggestions? Is this to be expected?

01-16-2009, 11:37 AM   #2
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a couple of points here, the "red confirmation' is not the focus confirmation, but an indicator of which focusing sensor is in use.

Second, and this assumes you are not cropping the image, but the 2GB is NOT where the focus sensor is located, the focus sensor (assuming middle one in use is in the middle of the frame where the nicely focused USB lable is located.

I see nothing wrong.
01-16-2009, 11:41 AM   #3
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It does beep for a reason though, right?

Also, I should have mentioned the image has been cropped. I centered the focus screen on the 2gb.
01-16-2009, 11:42 AM   #4
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What focus mode?

How's your focus setup? I.e. are you using the center mode? Auto? Select? That could make a difference in where it focuses. I know using Auto really frustrated me until I started using the Center setting.

Just a thought.

Bill B.

01-16-2009, 11:45 AM   #5
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QuoteQuote:
How's your focus setup?
I always use the center mode.
01-16-2009, 11:49 AM   #6
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Keep in mind that although they are called focus "points", they really ought to be called "vague focus-ish regions".
01-16-2009, 11:51 AM   #7
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did you use a tripod or mechanical support?

No offence but i find many times focusing issues are because the photographer moved the camera either in / out or up / down, and did not focus on what he thought he did.

also are you in continuous or single focus mode?

I really hate focusing discussions only because they are fll of possible errors.

with respect to the indication,, it is the green hexigon at the bottom, and you may find that depending on the direction you approach focus from, you can get both front and back focus.

Auto focus is nice but no system is fool proof.,
01-16-2009, 11:51 AM   #8
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QuoteQuote:
Keep in mind that although they are called focus "points", they really ought to be called "vague focus-ish regions".
I see. I guess I need to rely on my eyes more when focusing.

01-16-2009, 11:52 AM   #9
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Several others things to be aware of:

1) The focus adjustment is for AF, not MF. While it might also affect the focus confirmation, I wouldn't count on it - no one really knows exactly what it does. Chances are pretty good it really doesn't affect the detection of focus, but rather, the mechanics of turning the focus ring (or the SDm equivalent).

2) The actual focus sensor is much bigger than the little red square. So the square might light up in one place but it might actually be focusing somewhere a bit different. It's giving a general idea of where the focus was detected, no more. If you're trying to focus that specifically, you cann't depend on the confirmation.

3) Even at f/2.8, DOF can be shallower than what appears in the viewfinder, enough that something can appear in focus in the viewfinder but not be in focus in the picture. That's just a fact of life with the Pentax focus screen, which has a minimum DOF it is capable of displaying.

QuoteQuote:
My old DS2 nailed the focus with the same lenses.
Probably not with the exact same test - the problem is probably with the test, not the cameras or lenses. Your test includes too much stuff at different distances all within the rather large area covered by the focus sensor.
01-16-2009, 12:15 PM   #10
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QuoteQuote:
My old DS2 nailed the focus with the same lenses.
QuoteQuote:
Probably not with the exact same test - the problem is probably with the test, not the cameras or lenses. Your test includes too much stuff at different distances all within the rather large area covered by the focus sensor.
I'm not entirely convinced. I pulled out my DS2, mounted the same lens as on the K10, and it focused exactly on what I wanted it to. The K10d is always focusing on the area behind my subject, no matter what I do. I've confirmed this on multiple subjects.
01-16-2009, 12:17 PM   #11
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Do you get the same error (backfocusing exclusively, same offset at same subject distance), when moving towards focus from both directions (infinity->closeup, closeup->infinity).
With my k100d, sometimes the focus confirm lags quite a time, so when it shows up you might already be past the focus. It flashes, beeps, but then the green dot disapears..

If you use focus trap or press the shuter instantly, you might not notice that. With some lenses/in low light, i have to double or triple check/hunt for the focus to be trully confirmed.
01-16-2009, 12:26 PM   #12
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QuoteOriginally posted by Bill B Quote
How's your focus setup? I.e. are you using the center mode? Auto? Select? That could make a difference in where it focuses. I know using Auto really frustrated me until I started using the Center setting.

Just a thought.

Bill B.
Manual focus always uses the center point

Steve
01-16-2009, 04:09 PM   #13
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QuoteOriginally posted by quattro Quote
I'm not entirely convinced. I pulled out my DS2, mounted the same lens as on the K10, and it focused exactly on what I wanted it to. The K10d is always focusing on the area behind my subject, no matter what I do. I've confirmed this on multiple subjects.
Are any of them legitimate focus test charts that don't confuse the issue like the subject you posted her? That's the only way to be sure - you need a target that is smaller than the AF sensor and has nothing else around it that the sensor could possibly choose instead. That virtually never happens in real life, which is why you need a well-designed focus test chart. I like the one at focustestchart.com.
01-16-2009, 04:29 PM   #14
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The focustestchart.com site is apparently down for repairs or something
01-16-2009, 05:21 PM   #15
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Another question: how does your K10D behave in "real world" shooting?

Jer
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