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03-06-2010, 08:07 AM   #1
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question about K7's AF sensors

(I've posted a proper introduction in the 'Welcome' forum, but it hasn't been published yet, so I'll repeat a couple of things here)


I will soon be a K7 owner (ordered one from Amazon UK, should be delivered next week), coming from Sony/Minolta.
My previous camera (A700) has a double-cross sensor in the center, and another 10 line sensors across the frame. The center sensor provides better AF accuracy and locking speed, but there's a catch: the double-cross thingy kicks in only when using F2.8 or faster lenses, with slower ones it acts like the other sensors. While it may not seem like much, it does make a difference when shooting in low-lighting conditions (I had a couple of situations when the outer sensors would not lock focus at all, and I was limited to the center one).

Now... I'm wondering if the K7's AF sensors have such limitations as well?


Thank you!



PS- it matters to me because I'll be using a 15/F4 and a 17-70/F4, amongst other lenses.

03-07-2010, 11:54 PM   #2
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K7 Auto focus

I have found the K7 focus options to be excellent. You can choose from centre focus or to one of 11 points, depending on your settings. You can even adjust your focus within the settings menu for all, or a single lens. To sum up, ...rest easy until you get your camera and it will all work out fine. Make another post if you have any trouble.
03-08-2010, 01:31 PM   #3
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Thanks for the reply!

I knew about the AF options and micro-adjustment, I was just curious if there will be differences in AF performance depending on the max aperture of the lenses. But I guess I'll find that out soon enough, won't I?


EDIT- just to be clear: I know all 11 sensors are cross-type, not line-, like with Sony, so the accuracy and AF capability in low-light should be an improvement based on this only; AF speed... it doesn't matter that much to me
03-08-2010, 02:26 PM   #4
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QuoteOriginally posted by cezarL Quote
EDIT- just to be clear: I know all 11 sensors are cross-type, not line-, like with Sony, so the accuracy and AF capability in low-light should be an improvement based on this only; AF speed... it doesn't matter that much to me
I don't know about that... I'm not familiar with Minolta/Sony auto focus performance, but Pentax low-light auto focus performance tends to suck a big fat lemon. I find it more than adequate in bright light, but lower the ambient light a bit, and all my lenses do poorly. Even my F2.8 zoom.

However, I see no difference between my F2.8 zoom and my F3.5-5.6 kit lens or my F3.5-4.5 1990's kit lens. So my assumption is that the speed of the lens doesn't seem to affect auto focus performance negatively (or positively).

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