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Old Sep 13, 2006, 12:33 AM   #1
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Hey all, I have heard a bunch about 9 point AF and 45 point AF lately. So what does this mean? What kind of AF do most cameras have, which kind of cameras have a better AF? Is it a huge difference?

Also, my camera (Kodak P850) has this kind of AF.

TTL-AF hybrid autofocus system with external passive sensor

What does that mean?

Thanks, Keilan
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Old Sep 13, 2006, 4:51 AM   #2
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There's a description here that answers some of your questions. http://electronics.howstuffworks.com/autofocus.htm

The number of autofocus point can help the camera focus on the right part of the scene. Early autofocus cameras had a single autofocus sensor right in the middle of the screen. Whatever was in the middle was in focus, if your main subject was to one side it would be out of focus, unlessyou took action to focus on that area of the scene then reframe the shot. Now with multiple sensors the camera analyses the scene and tries to determine where too focus, this often works well but not always.

DSLRs have less autofocus sensors than compacts. Many have just 5 sensors but up to 11 sensors are becoming more common. They need less sensors because the photographers using them are generally more willing to take control of the shot and the viewfinders used are better for determining when the subject is in focus. With a DSLR and some compacts, including yours, you can select which focus point is active.

As to which is best it's horses for courses. Rather than how many sensors I'm more interested in speed and accuracy.


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