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HelicopterAerial Photography and Video › focal points question - center point or automatic?
07-13-2008 10:47 PM  9 years agoPost 1
FLAP

rrKey Veteran

Michigan

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I use canon DSLR's, but I think this is relevant to all SLR's.
I was going through the software that comes with my Canon (XT). I looked at the option which shows where the focal points were on each photo. On the Canon, there are 7, 5 across, 3 up and down (center shared). On all of my photos for the last year, only the top focal point was set. (top of the focal point cross, right above the center focal point. I must have accidently selected it manually at some point and that is where it stayed. I don't think it make a huge difference to my shots, but probably didn't help on some of them.

Now, this prompted me to actually read my instruction manual. I have the option to let the camera auto select the focal points or I could manually select one (I'm thinking the center point would be best).

Any opinions on this one? Automatic the best or center point?

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07-14-2008 12:06 AM  9 years agoPost 2
IKA photo

rrApprentice

Honolulu, HI

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For AP, I use auto select on my XTi. Its faster, and more likely something will be in focus. If you lock it on a certain spot and it for some reason connot focus on it, it will not shoot, or will search throughout the focus range, and it still may not shoot or take longer. Everything should stay in focus anyway. unless you are really close to the ground with objects in the foreground, and even then, the auto select is pretty good. Try the auto select on the ground while shooting handheld, Its surprising what it ignores. it usually focuses on the dominate subject.

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07-14-2008 02:18 AM  9 years agoPost 3
CKY

rrVeteran

Sunshine Coast, BC, Canada

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All the focal point sense points in the camera need hard edges or a definate pattern within a very small box at that point.

With only one point working for you I would assume you had a lot of Focus Misfires??

Different points may need different focal lengths, the camera will give a smaller aperture to compensate for the DOF.

The more points working the better. Only want one point if you have complete control of the camera and want to force the focus, usually using a wide aperture.

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07-14-2008 03:01 AM  9 years agoPost 4
tabbytabb

rrElite Veteran

seattle

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On certain cameras (5D for one) and certain lenses (F2.8 or faster) you get better AF performance by selecting the center point. In this case I usually select the center point.

Tabb

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07-14-2008 03:12 AM  9 years agoPost 5
FLAP

rrKey Veteran

Michigan

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With only one point working for you I would assume you had a lot of Focus Misfires??
That is correct! Sometimes it just would not fire (this was using it in non-AP mode as well). I will have to go back and do a little experimenting now, but I think the 'misfire' problem was mostly on the 10-22mm wide angle. Really had me scratching my head. I don't think, for some reason, the problem was as bad with the standard 18-55mm lens.

I'll have to give the center only thing a go as well.

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07-14-2008 03:34 PM  9 years agoPost 6
meflyjeep

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On the ground and in the air ...

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I stay with the center focus selector / indicator ... not to be confused with the focal point of the lens.

meflyjeep

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07-14-2008 05:40 PM  9 years agoPost 7
FLAP

rrKey Veteran

Michigan

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yes, slightly different things.

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