Automatic Auto focus points

[Henry Wilt]

How does AF work when using the automatic setting?
The reason I ask is that I was shooting away trying to capture my daughters 10th birthday party on Saturday and I have missed the focus on quite a few of the shots, not too badly as I was trying to keep the DOF pretty wide. I had the camera set to use the Automatic AF as the kids were moving around pretty damn quickly and I figured this was my best chance to get the shots. When viewing the shots with the Canon s/w I can see the focus points (PS. is there a way that I can see this in Lightroom?), sometimes just 1 point sometimes up to 3 points were used but not always where I wanted the focus. Now I know that the camera can't guess on exactly what I want to focus on but I thought that it would be centrally weighted, which I guess is not the case.
If anybody can explain how it works and/or the best way to use it I would be most grateful.

[Swisstony10]

I never could get my head around how the Canon AF system chose which focus points to use. After a very frustrating first few days with mine, I just switched to a single fixed point and I've used that ever since.

It's worth practising at being able to select a different focus point "on-the-fly" (there's a related thread on the "Photographing People" board) until you can do it without even taking your eye from the viewfinder - you'll find that you miss far fewer great shots then..

Russ.

[RichardTaylor]

See page 66 & 67 of your instruction manual.

[Swisstony10]

Instruction manual? What's one of those?

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Oh, do you mean the thing that's wedged under the short leg of my kitcen table?

Generally, it focuses on the closest object it can focus on.

Since I normally shoot at really large appetures (f2, or f2.8), I have to be very picky about my focus point. I always choose manual focus points, and recommend that all photographers get used to doing so. 99% of the time, I have the focus point in one of the 4 corners (i.e., the 1:30, 4:30, 7:30, or 10:30 position if you were to reference the points to a clock) which puts the focus at the intersection of the "rule of thirds" line.

My wife always got annoyed at me using manual focus points, because I'd never set it back to auto when I was done. Then she shot a wedding with me and had many fuzzy photos of the bride and groom (focus was on the back of someone's head) when using auto focus points. Now she always sets the focas points too.

It sounds hard, but you get used to it pretty fast.

[Henry Wilt]

Thanks Russ, I had gone for the Automatic as I had very little success with the selected points the weekend before at my other daughters Taekwondo competition. I guess I'll have to try again. Thanks for pointing me to the other thread also, it has started to cover some of the questions I have about spot metering, but that's a whole other topic I am trying to research.

Thanks Richard, I know how to set it (and where it is in the manual) but unfortunately the manual doesn't explain how it works or how to get the best out of it. As I am very new to this whole subject I was hoping for someone with some experience to maybe shed some light on the matter for me (and yes, I had searched this site and google for some answers but guess I was putting in the wrong questions, just another sign of my inexperience I guess ).

[Henry Wilt]

Thanks Photoboothguy, as I said in the reply I was writing as you posted this, I did try manual focus points the previous weekend and I was mainly using 1:30 and 10:30 (to use your analogy) to try and keep both competitors in my viewfinder while ensuring I had focus on one of them ready for when they came together - well that was the theory anyway, very little success I'm afraid. It's sounds though as if it is something that takes quite a bit of practise, so that's what I'll do.
Regarding the automatic points, it just seemed random which points it had picked eg. in one picture with my son in the pool, it has used the points at 3:00 and 9:00 which were the edge of the pool behind him. This is why it has confused me so much.

[wulf]

If you are not taking snapshots, then you should have a subject in mind for each photo you take. Since you cannot telepathically communicate that with the camera, it makes sense to learn how to use various focussing strategies (eg. single point, point and recompose, manual focus, pre-set fixed focus) so that you can get what you want nice and sharp.

There are exceptions, such as fast moving flurries of children, and AF systems are pretty clever these days but I suspect you have to take a lot more shots to get an apparent good hit rate on the final results.

Wulf