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Old 21st of March 2007 (Wed)   #1
mxp
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Default cross-type AF point on 10D ?

does the eos 10D have a cross-type AF point ?
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Old 21st of March 2007 (Wed)   #2
John_B
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Default Re: cross-type AF point on 10D ?

mxp,
Yes on the center AF point only
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Old 21st of March 2007 (Wed)   #3
Doug Pardee
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Default Re: cross-type AF point on 10D ?

As John said, yes the center AF point is cross-type. However, it doesn't have the triple-precision f/2.8 sensor that the 9-point AF on the 20D/30D/XTi/400D has.
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Old 22nd of March 2007 (Thu)   #4
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Default Re: cross-type AF point on 10D ?

Can someone go into more detail regarding this topic - its interesting to me and I would like to learn more. What exactly is a cross-type AF point vs. the other AF points in the 10D or any other camera for that matter?
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Old 22nd of March 2007 (Thu)   #5
Doug Pardee
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Default Re: cross-type AF point on 10D ?

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Originally Posted by bauerman View Post
Can someone go into more detail regarding this topic - its interesting to me and I would like to learn more. What exactly is a cross-type AF point vs. the other AF points in the 10D or any other camera for that matter?
Most AF sensors are only sensitive to edges that go in one general direction: either horizontal edges or vertical edges, but not both. A cross-type sensor is sensitive to both horizontal edges and vertical edges.
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Old 22nd of March 2007 (Thu)   #6
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Default Re: cross-type AF point on 10D ?

But this functionality is only available within the confines of certain apertures? Does that change depending on the lens that you have attached to the body?

(Thanks that explanation by the way - makes a lot of sense and is not something I was familiar with before now.)
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Old 22nd of March 2007 (Thu)   #7
Doug Pardee
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Default Re: cross-type AF point on 10D ?

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Originally Posted by bauerman View Post
But this functionality is only available within the confines of certain apertures? Does that change depending on the lens that you have attached to the body?
The autofocus system on the 10D, as on all of the Canon DSLRs except the 1-series, is designed for lenses of f/5.6 or faster. Yes, it depends on the lens (and often on the current focal length setting), because autofocus is done with the aperture wide open. What counts is how wide the lens aperture can go (at the current focal length setting).

There are some third-party zoom lenses that are f/6.3 at the long end, but lie to the camera and claim that they're f/5.6 so that the camera will autofocus.

The 9-point AF system used on the 20D, 30D, and XTi/400D also has a triple-precision non-cross sensor—sensitive to vertical edges only—at the center AF point that is turned on when a lens of f/2.8 or faster is fitted. So with an f/2.8 lens, the center AF point is still cross-type and therefore still sensitive to both horizontal and vertical edges, but it gives more precise results with vertical edges. This triple-precision sensor is not present on the 10D or any of the other Canon DSLRs with the 7-point AF system.
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Old 22nd of March 2007 (Thu)   #8
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Default Re: cross-type AF point on 10D ?

Excellent information Doug - and much appreciated. It makes a lot of sense and I especially liked the bit about the "lying lenses" that fibbed that they were f5.6 so the camera would autofocus.

Are there any links or websites that you know of that explain this subject in more detail that you could point me to? Thanks.
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Old 22nd of March 2007 (Thu)   #9
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Default Re: cross-type AF point on 10D ?

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I especially liked the bit about the "lying lenses" that fibbed that they were f5.6 so the camera would autofocus.
I would stay away from those lenses. If they're lying they were f/5.6, they most likely "pretending" they achieve consistent focus. It's not Canon who's set a limit at f/5.6 for AF. It's the geometry of the AF sensor that won't allow a smaller aperture.
I don't have links, but you can google for PHASE DETECTION AUTOFOCUS.
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Old 22nd of March 2007 (Thu)   #10
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Default Re: cross-type AF point on 10D ?

Thanks adas - I will do that.
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Old 22nd of March 2007 (Thu)   #11
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Default Re: cross-type AF point on 10D ?

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Originally Posted by adas View Post
I would stay away from those lenses. If they're lying they were f/5.6, they most likely "pretending" they achieve consistent focus. It's not Canon who's set a limit at f/5.6 for AF. It's the geometry of the AF sensor that won't allow a smaller aperture.
I don't have links, but you can google for PHASE DETECTION AUTOFOCUS.
Then you are telling people to stay away from the Bigma. I have it and it sure does get AF right.
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