Can't hold focus lock when zoomed & wide open

[Derrel]

Canon EOS T2i (Rebel T2i, Canon 550D) Digital Camera Exposure - Full Review - The Imaging Resource!

"Through the Custom Functions menu, the behavior of the AE / FE lock button can be changed. By default, a single press locks exposure until the shutter is released, or the T2i's metering system powers down, while focus is locked with a half-press of the shutter button. There are three alternatives to this behavior. The first swaps functions so that the AE / FE lock button locks focus, and a half press of the shutter button locks exposure. The second alternative uses the AE / FE lock button to cancel continuous autofocus in AI servo mode, and to recalculate focus / exposure which are locked by a shutter button half-press in One Shot or AI Focus modes. Finally, you can opt to dedicate the AE / FE lock button to both focus and exposure, locking both variables with a single press unless using AI Servo focus, in which case the AE / FE lock button is solely used to trigger continuous AF operation."

I hope maybe this is the answer you're looking for.

 

[Lazy Photographer]

Canon EOS T2i (Rebel T2i, Canon 550D) Digital Camera Exposure - Full Review - The Imaging Resource!

"Through the Custom Functions menu, the behavior of the AE / FE lock button can be changed. By default, a single press locks exposure until the shutter is released, or the T2i's metering system powers down, while focus is locked with a half-press of the shutter button. There are three alternatives to this behavior. The first swaps functions so that the AE / FE lock button locks focus, and a half press of the shutter button locks exposure. The second alternative uses the AE / FE lock button to cancel continuous autofocus in AI servo mode, and to recalculate focus / exposure which are locked by a shutter button half-press in One Shot or AI Focus modes. Finally, you can opt to dedicate the AE / FE lock button to both focus and exposure, locking both variables with a single press unless using AI Servo focus, in which case the AE / FE lock button is solely used to trigger continuous AF operation."

I hope maybe this is the answer you're looking for.

Thanks a mil'. Yeah, I've read this in at least one of the books and really didn't get my head around it, to be honest. I think it's best understood through practice. I might take some time and try out various methods to see if any are more preferable than what I'm doing now. For now, though, I think I'll shoot in single shot mode and change it up as needed.