Canon 600D focus prior to shooting
To amplify EladRichi's last bullet item, be sure to check out this Canon Digital Learning Center Article:
"For sports photographers and others taking action pictures, back-button AF lets you stop focus whenever something might interfere with the moving subject you’re tracking — without requiring you to stop shooting."
|High Altitude Rocky Mountain Railroad by cjf2|
from On the Rails...
|Evening at the lake. by Murat ÜNSAL|