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09-05-2008, 11:32 AM   #46
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QuoteOriginally posted by Marilith Quote
Debug menu?
Which Model do you have?
*ist DS, old school... :-)

09-05-2008, 11:45 AM   #47
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QuoteOriginally posted by paulusta Quote
instead of focus-recompose,
why not using the SEL and choose which focusing area for AF?
Because all other AF points might not be as accurate as you think, seriously.
09-05-2008, 11:49 AM   #48
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QuoteOriginally posted by wlachan Quote
Because all other AF points might not be as accurate as you think, seriously.
Exactly! Specially outer left and right points, and more noticeable with faster glass

Regards,
D
09-05-2008, 11:50 AM   #49
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QuoteOriginally posted by Marc Sabatella Quote
As I said, the author of that article went too far. But I'm surprised that someone who prides himself on measuring things is unable to see the pretty obvious change in focus even with a lens with a much deeper minimum DOF, such as the DA40/2.8.
I think this good old practice since MF era to focus first then recompose worked well in most situations. The problem raises when using very large aperture or shooting at close distance. But based on my experience, this approach is no worse than AF error in most cases.

09-05-2008, 11:53 AM   #50
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QuoteOriginally posted by Duh_Vinci Quote
Exactly! Specially outer left and right points, and more noticeable with faster glass

Regards,
D
I have calibrated my own DS twice trying to get all 11 points in focus. I am able to get all 9 cross points in good (if not 100%) accuracy, but the far out 2 vertical sensors just kind of hit & miss in practice.
09-05-2008, 08:26 PM   #51
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QuoteOriginally posted by jamonation Quote
Umm, why recompose when you can just manually focus correctly in the first place? Give me a grand and I'll go pick up an 85mm f1.4 any day though Dunno why I'd want to use AF with it, just my personal preference I guess.
I meant to use *real* MF cameras, of which the MF focusing facility/aids (no matter what) is at the centre.
09-05-2008, 08:29 PM   #52
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QuoteOriginally posted by paulusta Quote
instead of focus-recompose,
why not using the SEL and choose which focusing area for AF?
Use only the central AF point as far as possible as all other points are just less accurate with less precision and sensitivity.
09-05-2008, 11:08 PM   #53
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QuoteOriginally posted by Marc Sabatella Quote
Actually, that's to be *expected*. See the following link:

Why Focus-Recompose Sucks

The author goes too far - most lenses do in fact have a somewhat curved "plane" of focus, not flat as the author assumes. Flat focus planes are one of things that make true macro lenses different from ordinary lenses with a close-focusing feature.

Anyhow, bottom line: any time you change your camera angle, the "plane" of focus changes with you. If you only move a little, or you have a small aperture, it shouldn't matter. But it matters a lot with large apertures and/or if you put the subject all the way to the edge of the frame.

A simple way to test what is going on: first take the picture *without* recomposing. Is it in focus? If so, the camera has done it's job, end of story. If the subject is out of focus after recomposing, you are seeing exactly the effect describe in the above article. It's not the camera's fault - it's just a flaw in the technique itself. Assuming, of course, you are not in AF-C mode or haven't inadvertently triggered a second AF operation after the recompose.

If on the other hand the subject is out of focus even without recomposing, then you may have a FF/BB problem worth investigating.
That all good and fine when talking about f2 or better lenses. I'm not. I stop down to f5.6 or f8 trying to mitigate this issue. The biggest problem I have with it is it's consistancy. It can do it, just not reliably. The reason I have reverted to this method is because the AF point can't reliably focus on a single face. I though giving it a larger area might help.

I have printed out the BF test charts so will pursue that, although once again, I don't think that's a problem because it can do it right!

regards, Nige

09-06-2008, 12:34 AM   #54
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The Main Design Flaw..

QuoteOriginally posted by HGMonaro Quote
The reason I have reverted to this method is because the AF point can't reliably focus on a single face. I though giving it a larger area might help.
This applies to the Pentax's (DSLR AF) system *only*, but not others, not even Pentax's AF system of their film SLRs.

The problem of the SAFOX VIII is that the sensors cover a too large area in the frame. This causes two issues: 1. too much patterns on different subjects are projected, and thus cause confusion and errors; 2. The resolution/pixel density of the AF sensors decreased (unless Pentax made very large sensor with normal density, but not magnify the area - which is unlikely as this increases manufacturing cost much but with no real advantages).

Pentax used to make only larger area AF point for only a few entry level film AFSLRs as they know only beginners need such a larger coverage per point, but now the SAFOX VIII is the largest forever in terms of the area but it lacks precision, which would be the main cause of such an inferior AF system and the "unavoidable" AF huntings.
09-06-2008, 06:28 AM   #55
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QuoteOriginally posted by RiceHigh Quote
and the "unavoidable" AF huntings.
that's one thing I don't have a problem with!
09-06-2008, 07:57 AM   #56
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QuoteOriginally posted by HGMonaro Quote
that's one thing I don't have a problem with!
I guarantee that under circumstances that you don't have a problem, you won't neither with any of other DSLRs of any model or brand. But the vice versa will not be true.
10-16-2008, 04:38 AM   #57
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QuoteOriginally posted by medbooks321 Quote
For those of you who are sticking with Pentax, how have you made it focus better in low light? Or is it a matter of skill? Perhaps I need to practice more ...
As one review stated, using the AF assistance from external flash; ”turns the Pentax DSLR into an indoor champ”.
(Metz also builds some great flashes for the Pentax system).

I’ve used my Pentax film SLR Z-1P in lots of low-light, and never had much problems. Sometimes the built-in AF assist light gave out its veil to assist, other times the camera managed itself.

The D300 and D700 are better in AF department, than Pentax.

But the K20 is an improvement even over the K10. Do you use good batteries in your K100 ? Else the new K-m should have improved AF algorithm as well. And the K30 is expected next summer, with new AF system.

Norm had a good thread on how to optimize and get the most out of your Pentax system :
Norm's tips for low-light auto focus performance [Page 1]: Pentax SLR Talk Forum: Digital Photography Review



QuoteOriginally posted by hinckc Quote
I've also been practicing with de-coupling AF from the shutter button. The K100D doesn't have a dedicated AF button, but you can set the OK button to this function. See pg 126 in the manual for details. This, too, requires practice, but I really like leaving the camera in AF-C, and using the AF button to focus. That way, I can take a shot whenever "the moment" arrives, all the while tracking my subject as best as the AF can do until I'm satisfied with the focus. When it finds it, I can leave the AF button alone until I shoot.
-Chris
Thanks, good tip


QuoteOriginally posted by RiceHigh Quote
I guarantee that under circumstances that you don't have a problem, you won't neither with any of other DSLRs of any model or brand. But the vice versa will not be true.
Yes, because a guaranty from you is really worth a lot, or something…

A “Pentaxian”, who does the outmost not to recommend the brand.
10-16-2008, 06:25 AM   #58
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QuoteOriginally posted by RiceHigh Quote
I guarantee that under circumstances that you don't have a problem, you won't neither with any of other DSLRs of any model or brand. But the vice versa will not be true.
The problem here is that most of the people on this forum just don't know what a real high performance camera is. I had the pleasure of using a Nikon D3 yesterday, and then making prints from the resulting files.
To say I was impressed is an understatement. To say I was completely blown away is closer to the truth.
The camera outperformed anything I had used before on every level that I use to judge a camera's performance.

Before anyone trots out the tired old "my Pentax is cheaper" argument, remember that your Pentax being cheaper is the problem, not the solution.
10-16-2008, 04:31 PM   #59
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QuoteOriginally posted by Marilith Quote
Debug menu?
For your K100D, check this page: focus w k100d - CyberFoto.pl - Aparaty Cyfrowe
Note that "Press [MENU], you can see setup menu." should read "Press the menu button and navigate to the setup menu".
10-16-2008, 04:46 PM   #60
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QuoteOriginally posted by Wheatfield Quote
The problem here is that most of the people on this forum just don't know what a real high performance camera is. I had the pleasure of using a Nikon D3 yesterday, and then making prints from the resulting files.
To say I was impressed is an understatement. To say I was completely blown away is closer to the truth.
The camera outperformed anything I had used before on every level that I use to judge a camera's performance.
The problem here is assuming that Pentax makes a real high-performance camera. Comparing anything Pentax currently offers to the D3 is completely pointless. The Nikon is in a completely different class, performance- and price-wise.

If you need what the D3 offers, Pentax is not the place to be looking for it.

QuoteQuote:
Before anyone trots out the tired old "my Pentax is cheaper" argument, remember that your Pentax being cheaper is the problem, not the solution.
You've got that backwards. Pentax being cheaper is not a problem. Expecting a K20D to perform like a Nikon D3 is.
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