I know I'm being really thick, but I still don't understand, the way I see it you're having to do more, you still have to half press (and full press obviously) the shutter but you also have to press the back button.
I tried it for a week or so years ago, never liked it. I don't quite see the benefit either, but I also don't take photos of sports or animals, no gain for me, one more button to press. But obviously many here love it for some reason or other. Maybe I'll try it again some day, but probably not. I do use the * for meter lock occasionally. My friend uses BB on all his cameras, but also could not explain to me why I should do so. I never noticed a lag of any kind. Might be more depending on what you shoot? runners, race cars, fast birds, ball games? All things of little interest to me, may be I just never came across the supposed limitations the standard setting has?
Curious, was this also a feature on pre digital cameras?
I think the feature existed for a long time. it's great for many scenarios. The goal is to decouple the autofocus from the shutter button.
it's like exposure lock right? You lock your exposure and you dont want to change it.
I can be shooting a portrait and lock focus on the eyes. I dont want my next shot re-acquiring focus again and possibly lock on the background or nose.
I can be shooting in the streets, and lock on a object near a crowd. as people walk by, I dont want to inadvertently lock on them instead.
Bride and groom exchanging vows. You get the first shot, and something funny is said, and change of expression. You dont want to acquire focus again and possibly miss that shot and land focus on the priest.
You can set your custom mode to use BBAF if you're not comfortable and switch back and for with conventional shutter AF. That's how I setup in case I want to hand over my camera to someone else.