Focussing strategies with moving subjects

[kat.hayes]

I want to use a 5DM3 and a 100-400 to shoot both photos and videos of kids doing gymnastics from a distance. The kids will be still in one spot and then run and do somersaults.

1.Is it better to use manual or auto focus for this?
2. If I choose manual focus, I can zoom in and focus on the subject before they start moving to achieve sharp focus, though once they start running, how do you ensure the focus is maintained?

Thanks.

 

[ajfotofilmagem]

With this combination camera + lens, using manual focus for fast moving objects, would be a waste of money.

Test before the big day, at distances and lighting similar to the event. Enjoy to determine what shutter speed is sufficient for the type of movement that the kids will do.

Try only the central focus point, focus zone, and all focus points, and then analyze on the computer what mode is your hit rate.

If you use the "one shot" mode, the camera will only focus on the first shot of each burst, even if you take 6 shots per second.
If you use "AI servo" mode, the camera will continually readjust the focus between each shot, and there are many custom options you need to test to see which one fits the type of movement of your objects in AI servo.

 

[Mt Spokane Photography]

I do that with theater shots, using my 5D MK IV and 70-200L. I don't get far enough away to use the 100-400. If the distance is long enough, you might get away with having everyone within the depth of field, but autofocus is so much better. Put the camera in AI Servo and let it keep the subject in focus as they move. Just make sure that the subject is fairly large in the viewfinder.