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01-16-2009, 05:34 PM   #16
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QuoteQuote:
Another question: how does your K10D behave in "real world" shooting?
I agree my focus test is not exactly scientific, but I seem to be missing the focus in many 'real world' shots. The sample pic was just an example of this. The other day I took a pic of someone infront of a sign, instead of focusing on the face, as the viewfinder seemed to show, the sign was in focus.

01-16-2009, 06:42 PM   #17
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QuoteOriginally posted by quattro Quote
I agree my focus test is not exactly scientific, but I seem to be missing the focus in many 'real world' shots. The sample pic was just an example of this. The other day I took a pic of someone infront of a sign, instead of focusing on the face, as the viewfinder seemed to show, the sign was in focus.
If the viewfinder really showed the person more in focus that the sign, and the picture showed it the other way around, that would indicate a problem. But simply having chosen to focus on the sign instead of the person wouldn't be a defect, assuming the both were in range of the AF sensor. So you really need to do a controlled test where you are absolutely positive about what you are seeing in the viewfinder. And as I've pointed out many times, the viewfinder *will* show you more in focus than actually is, so it is absolutely 100% normal for some things to be in focus in the viewfinder but not in the final image. But it is *not* normal for the opposite to happen - you should never have things out of focus in the viewfinder bu in focus in the final images (at wide apertures, anyhow - obviously, that happens all the time at smaller apertures unless you take advantage of the DOF preview).
01-16-2009, 06:53 PM   #18
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QuoteQuote:
If the viewfinder really showed the person more in focus that the sign, and the picture showed it the other way around, that would indicate a problem. But simply having chosen to focus on the sign instead of the person wouldn't be a defect, assuming the both were in range of the AF sensor. So you really need to do a controlled test where you are absolutely positive about what you are seeing in the viewfinder. And as I've pointed out many times, the viewfinder *will* show you more in focus than actually is, so it is absolutely 100% normal for some things to be in focus in the viewfinder but not in the final image. But it is *not* normal for the opposite to happen - you should never have things out of focus in the viewfinder bu in focus in the final images (at wide apertures, anyhow - obviously, that happens all the time at smaller apertures unless you take advantage of the DOF preview).
Thanks for the help. I'll need to further investigate in a more controlled environment with a focus chart and tripod.

Setting the "Focus Corr" to +200um in the debug menu seems to help a lot. At 0um, objects appear to be out of focus (ex. the USB logo in the sample pic) in the viewfinder, but are actually in focus in the final pic.

I'm fairly confident I know how it "should" work. The K10d is new, but i've done 7000+ shots with the DS2, and could always rely on what my eye saw through the viewfinder. Thanks for the help.
01-16-2009, 11:25 PM   #19
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QuoteOriginally posted by quattro Quote
Setting the "Focus Corr" to +200um in the debug menu seems to help a lot. At 0um, objects appear to be out of focus (ex. the USB logo in the sample pic) in the viewfinder, but are actually in focus in the final pic.
And changing the menu setting altered that? That should be impossible. If the viewfinder picture doesn't match the actual picture in that way, this means one is physically misaligned. The menu settings doesn't physically move anything.

QuoteQuote:
I'm fairly confident I know how it "should" work. The K10d is new, but i've done 7000+ shots with the DS2, and could always rely on what my eye saw through the viewfinder.
The DS2 is no different from the K10D in this respect - both show more in focus in the viewfinder than will be in picture in the actual picture. You must never have noticed. Did you ever actually try doing this sort of focus test on the DS2?

01-17-2009, 02:32 AM   #20
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QuoteOriginally posted by quattro Quote
The K10d is always focusing on the area behind my subject, no matter what I do. I've confirmed this on multiple subjects.
Another possibility is that the AF sensor is not where your focusing screen shows it to be. Sometimes the alignment is not correct so you are not aiming with your focus where you think you do.

I agree that you should try another test setup in order to make sure that you unambiguously know where the camera focused.

FWIW, I find Tim Jackson's focus test chart suboptimal in this respect because you never know whether the camera tried to focus at the top or the bottom part of the bar. Not a big difference and certainly way better than your current test, but if one goes through this, why not use a single big black-white transition? I'm preparing my own focus test chart but didn't get round to testing it yet.
01-17-2009, 06:19 AM   #21
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The center sensor is almost as big as the circle in the viewfinder, and as soon as anything in that area is in focus the confirmation lamp lights up. So depending on the target it can make a huge difference if you turn the focus ring from infinity or from close up.
01-17-2009, 09:23 AM   #22
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QuoteOriginally posted by Class A Quote
FWIW, I find Tim Jackson's focus test chart suboptimal in this respect because you never know whether the camera tried to focus at the top or the bottom part of the bar. Not a big difference and certainly way better than your current test, but if one goes through this, why not use a single big black-white transition?
Agree, that's probably better. But I haven't liked other aspects of charts I've seen that incorporate this. I like the simplicity of Tim's chart. And I've yet to use a lens with DOF so shallow that the difference between the front and back edge of the bar was significant enough to affect the results.
05-03-2010, 09:48 AM   #23
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Could it be that these focusing issues sometimes are there, and sometimes are NOT there? I remember being frustrated at times about the back focus produced by my K10d. But at other times it all went well. Lighting conditions might be a cause.
The fact that focus indicator is not the exact spot for the autoocus ws new to me, but new test shots indicate that the problem can not be solved by this awareness.

This is most certainly a reason to restart considering a new camera. But the K20d and K-7 have the same issues, or haven't they?

K10d V 1.30

05-03-2010, 01:47 PM   #24
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QuoteOriginally posted by Syb Quote
I remember being frustrated at times about the back focus produced by my K10d. But at other times it all went well. Lighting conditions might be a cause.
All pre-K-7 Pentax DSLRs are known to FF under Tungsten lighting. So if you experienced BF in daylight and correct focus inside that could be explained by a miscalibrated AF system and the "Tungsten effect".

The K-7 (and probably the 645D) got this fixed.

QuoteOriginally posted by Syb Quote
The fact that focus indicator is not the exact spot for the autoocus ws new to me...
Well, it is. You just need to know that the AF areas areas are bigger than the focus indicators. Here's a diagram of the AF areas. Most of the time they work just fine for me but their size explains why the camera can sometimes go for the wrong subject if it is also within the area and shows higher contrast then the one you intended to focus on.
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