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Old Jun 26, 2007, 7:50 AM   #1
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I have had my 30D for about a month now and I am very impressed with it. I was wondering out of the 9 points of auto focus what does everyone use as their point. I have been shooting with the center point set that way I can nail crisp eyes. Just wondering what everyone else ues.
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Old Jun 26, 2007, 10:09 AM   #2
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I have the 20D, not the 30D, but I can say yes, I use the center point the majority of the time.
When I'm close to my subject, and it isn't in the center I will change the focus point so it is over the eyes.

Some times this does work well (I miss the shot changing the AF point, for example) but usually it does.

The problem, if you don't now, is that if you have multiple AF points selected it will choose the AF point where the thing underneath it is closest. Imagine your subject is a child standing partially sideways. If one AF points is over the shoulder and the other is over the face, it will lock focus on the shoulder because its "closer" than the face. Not what you want.

I assume this is what the "Face detection" question was about earlier... maybe something can detect that you probably want the face instead and pick the right AF point. Or maybe they'll move the eye focus tracking system from canon's film camera days so it can detect that I'm looking at the face.

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Old Jun 26, 2007, 10:13 AM   #3
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I'm a 30D and 5D user and 95% of the time they are both in centre point focus. If I give one to a friend to use then I might switch it to all points but that's about it. There are occasions when shooting sports that one of the diagonal ones givesa better perspective on framing and also there are some motorsport shots where I find a better 'hit' rate by selecting all focus points.

The centre point is rated to f2.8 making it much more sensitive so you should get the best focus with this.
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Old Jun 26, 2007, 5:56 PM   #4
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Withall the cameras I have, and have had, I have always used the center sensor almost exclusively. Like mentioned before, it's usually the most sensitive and accurate one, and somehow the built in chip just never figures out what it is I really want. And I'm guessing never will...
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Old Jun 27, 2007, 5:40 AM   #5
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It's fairly obvious surely?

Use the focus point closest to where you want the point of focus to be in the shot.

Be very careful of using focus-recompose with the centre point if you have a very shallow DOF situation; it pretty much guarantees that you will be mis-focussing.
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Old Jun 27, 2007, 9:53 AM   #6
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peripatetic wrote:
Quote:
Be very careful of using focus-recompose with the centre point if you have a very shallow DOF situation; it pretty much guarantees that you will be mis-focussing.
Are you saying that the 1 or 2 millimeters of change in distance to the object by moving your camera a centimeter left or right is going to mis-focus your picture? Maybe in macro photography, but otherwise...? I would say in real life the swaying of your body creates more change in distance to the subject than recomposing from one focus point to another.
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Old Jun 27, 2007, 9:55 AM   #7
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peripatetic wrote:
Quote:
It's fairly obvious surely?

Use the focus point closest to where you want the point of focus to be in the shot.

Be very careful of using focus-recompose with the centre point if you have a very shallow DOF situation; it pretty much guarantees that you will be mis-focussing.
I agree to a point. But, other focus points are not cross-type so you have to understand how they detect contrast (only along a single axis). Also they're less sensitive

Given those two constraints,I find in very low light they are not accurate enough so if you don't have a still subject I have found I often have to use the center point anyway (without recomposing) and frame more loosely adjust the the composition via post processing. In good light, this isn't an issue and I'll use the closest point but in poor light I've found the non center focus points of my 20D to be not up to the task.
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Old Jun 27, 2007, 6:44 PM   #8
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Michi wrote:
Quote:
peripatetic wrote:
Quote:
Be very careful of using focus-recompose with the centre point if you have a very shallow DOF situation; it pretty much guarantees that you will be mis-focussing.
Are you saying that the 1 or 2 millimeters of change in distance to the object by moving your camera a centimeter left or right is going to mis-focus your picture? Maybe in macro photography, but otherwise...? I would say in real life the swaying of your body creates more change in distance to the subject than recomposing from one focus point to another.
Not sure what you mean there. Sometimes DOF is only a centimetre or two - under those circumstances focus-recompose will often guarantee you get it wrong.

http://visual-vacations.com/Photogra...pose_sucks.htm
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Old Jun 27, 2007, 6:47 PM   #9
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JohnG wrote:
Quote:
peripatetic wrote:
Quote:
It's fairly obvious surely?

Use the focus point closest to where you want the point of focus to be in the shot.

Be very careful of using focus-recompose with the centre point if you have a very shallow DOF situation; it pretty much guarantees that you will be mis-focussing.
I agree to a point. But, other focus points are not cross-type so you have to understand how they detect contrast (only along a single axis). Also they're less sensitive

Given those two constraints,I find in very low light they are not accurate enough so if you don't have a still subject I have found I often have to use the center point anyway (without recomposing) and frame more loosely adjust the the composition via post processing. In good light, this isn't an issue and I'll use the closest point but in poor light I've found the non center focus points of my 20D to be not up to the task.
I agree, actuall it's quite lucky that I have a strong liking for square format portraits, it allows me to use the centre point and crop the extraneous material. I am usually fully aware when I am shooting that I will be doing this, but sometimes it's a happy accident.
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Old Jun 30, 2007, 11:51 AM   #10
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peripatetic wrote:
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Not sure what you mean there. Sometimes DOF is only a centimetre or two - under those circumstances focus-recompose will often guarantee you get it wrong.

http://visual-vacations.com/Photogra...pose_sucks.htm
Well, I guess we all use different techniques, so there is no point arguing. The article is interesting but really states the obvious. On a close portrait, I would never focus on the chest to get the face focused correctly. I might focus on the eyes and then move the camera so the nose is centered.

Interesting also how it says "This has given rise to the technique of center point focus-recompose..." In the days of manual focus SLR's, this is ALL we used. We would focus our subject, then recompose our picture being fully aware of shutter speed and aperture, and hey, it worked...
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