Changing focus points after the event

I usually shoot sports for my kids, primarily T&F and cross country. For that I use my 7D with AF point expansion. Then after the events, we sometimes will have group or team shots which are much wider. Should I be switching to the full 19 point AF for those shots to minimize the chance of kids on the edges being in less than perfect focus? Thanks.

No. Focus point isn't depth of field.

As currently set, your camera will focus on the middle of the group photo (perfect) and you should adjust your ISO, shutter speed and f-stop to get the correct exposure and depth of field for the group shot.

Depth of field is dependent on focal length, f-stop and distance to subject. It varies, e.g., I could get a group in focus at f/2.8 if I'm far enough away from them; however, that clearly wouldn't work if I were up close.

Here's a great resource for this: http://www.dofmaster.c​om/dofjs.html

Thanks. It seemed that a few of the kids on the edges of the group were a little OOF. The center seemed OK, most of the time. I know that sometimes I was focused on the center of the chest and probably needed to remember to focus on the eyes. When they are running, I usually shoot for the chest just to keep them in the center of the frame

And thank you for that link!

duckster wrote in post #18733600
Thanks. It seemed that a few of the kids on the edges of the group were a little OOF. The center seemed OK, most of the time.

This has nothing to do with the focus point used. It is due to one of two things
1. The line is not straight/perpendicular to the camera sensor, so some people are not on the plane of focus and are thus slightly out of focus. As well as the useful Depth of focus link posted above you should also understand plane of focus http://www.photokonnex​ion.com/definition-plane-of-focus/ - anything on the plane of focus should be in focus and anything within the DoF should be less and less in focus but still appear acceptably in focus. Unless.....
2. Your lens is soft at the edges making those people look OOF. This is less likely but possible if you have a cheap lens.

Thanks.

Probably due to the former as the line of athletes was slightly curved to fit everyone in and the lens was a 100-400L. Thanks for the information