AF Focus Points--am I missing out on any parties?

Greetings,

First of all, it feels very very strange to me to be posting in a section other than the Post Processing one--I feel like I'm on a different site all together, on a different forum. Will people say, "Welcome, RandMan!" along with their responses? Oh my, I'm going off on a tangent. Here we go:

I have a t2i/550D. I consider myself deeply "in tune" with the camera--I usually shoot in Manual or Av mode, iso limits, RAW etc. so in other words I understand and utilize most of the more advanced features.

I feel like the only time I ever moved the AF focus point from its center position was the day I got the camera, and I was just playing around and testing all the buttons. I use back button focusing, use the center point to focus my subject, and then move the camera to compose the shot how I want. Obviously it works--it's all I ever do. But am I missing out on anything by not switching them around more often (I am excluding the feature of using all points and letting the camera decide what I want to focus on--blasphemy!!!)?

I think the main trigger that spurred this question is that I notice as camera bodies increase in price, they also increase in number of AF points available. So, enlighten me! How do you all use different AF points and how, why, when etc. I'm very curious to know.

-Randy

Newer af systems can help in a number of ways.

1. Having more points towards the outside of the frame means you have to recompose less. Personally, I find it easier to use the correct point rather than recompose. Especially when useing fast lenses where the act of recomposing can move the focal plane.
2. More importantly, what you are doing is really very hard to do with moving subjects.

dalto wrote in post #15918085
Newer af systems can help in a number of ways.

1. Having more points towards the outside of the frame means you have to recompose less. Personally, I find it easier to use the correct point rather than recompose. Especially when useing fast lenses where the act of recomposing can move the focal plane.
2. More importantly, what you are doing is really very hard to do with moving subjects.

I fully agree with your point about moving subjects. In this case, what are you doing exactly? Let's say a person is moving around in front of you or a child is running around outside. Which of the following would you do?

A) AI Servo
Portrait Orientation
Use all AF Points automatically (camera decides)

B) AI Servo
Portrait Orientation
Select the individual right side AF Point (which in portrait orientation will now be on
top). This assumes you want to focus on the face/head.

"Focus and recompose" does work most of the time for still subjects, but the plane of focus shifts when you recompose so that the subject is no longer in the plane of focus that you originally had. Depth of field will usually take care of this but if you are shooting at wide apertures it may not, so in this situation using one of the outer FPs and recomposing less will help.

"Focus and recompose" is not really an option for moving subjects, so if you use the center point you will likely have to crop the photo in PP to get the composition that you want. Using an outer FP will help you to do less cropping in PP.

I sympathize with you on how much trouble it is to have to change the FPs by hand and I do a lot of "focusing and recomposing" too, these days, for still subjects and small apertures. Back in the "olden film days" Canon had a great system for choosing a FP by just looking at what you wanted to be in best focus and the proper focus point was chosen by where in the viewfinder your eye was looking, rather than fumbling about with dials and buttons to choose the FP. It was called Eye-Controlled Focus Point Selection. Sadly this feature was dropped by Canon when the transition to digital SLRs occurred.

RandMan wrote in post #15918168
I fully agree with your point about moving subjects. In this case, what are you doing exactly? Let's say a person is moving around in front of you or a child is running around outside. Which of the following would you do?

A) AI Servo
Portrait Orientation
Use all AF Points automatically (camera decides)

B) AI Servo
Portrait Orientation
Select the individual right side AF Point (which in portrait orientation will now be on
top). This assumes you want to focus on the face/head.

Depends on what I am trying to achieve. If my goal is to have the adult in focus and the adult out of focus then I would use the individual point that would have the correct subject in focus as you describe in "B"

Otherwise, I would increase depth of field and use "A"

RandMan wrote in post #15918168
I fully agree with your point about moving subjects. In this case, what are you doing exactly? Let's say a person is moving around in front of you or a child is running around outside. Which of the following would you do?

A) AI Servo
Portrait Orientation
Use all AF Points automatically (camera decides)

B) AI Servo
Portrait Orientation
Select the individual right side AF Point (which in portrait orientation will now be on
top). This assumes you want to focus on the face/head.

With the T2i and the "A)" scenario that you describe above(AI Servo with Auto Focus Point selection), the camera will "choose" the center point to start with(this can be changed on some of the more advanced cameras but not on the T2i) and if the subject that achieved focus initially with the center point moves to another point then the camera will hand-off the focusing duties to the new point. This is great for a single bird in flight against a clear blue sky, but for most other situations it will be better to choose a single FP(even the center) yourself and then keep that FP firmly on the subject as it moves.