unfortunately r+f and f+r don't work with bbf, only shutter button mode. I think Cindy switches between shutter and bb but I get myself all confused, lol. I have to stick with bbf full time.
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hark , something else to play with is menu a4. The purpose of this setting is to decide how long the camera waits before letting itself be distracted by an intruder in the frame. But it also works in the other direction. It is messing with me in bbf with single point. Say if I am focusing on that egret's head with constant press of the bb, a4 affects what happens if I wobble that single point off the head. With A4 set on fast, it will instantly refocus on the background. Set to the slow side, it will give me a small grace period before it jumps to the background. The downside to setting it slow is if focus does jump to the background, it will delay before refocusing on the bird when I get on target again. There is no right or wrong here but I think I like it set to fast response.