Back-button focus: why?

[Joel Eade]

I have been using back button focus exclusively for at least 2 years. It works very well for birds, especially flight shots where you can continuously adjust focus with your thumb and shoot with the index finger. Also, even though I may be in AI Servo, it can mimick One Shot mode in that you can focus using the back button and then re-frame the image before firing the shutter. I was unsure at first but it seems very natural and easy to use.

[peety3]

It works very well for birds, especially flight shots where you can continuously adjust focus with your thumb and shoot with the index finger.

Just playing devil's advocate, you can continuously adjust focus with your index finger and shoot too.

Also, even though I may be in AI Servo, it can mimick One Shot mode in that you can focus using the back button and then re-frame the image before firing the shutter.

Extending the devil's advocate, this is probably a rare thing, so why "work" for 85-95% of your shots to mimic One Shot when you could instead remap AF-ON to be an AF-OFF button for that 5-15% of your shots to mimic One Shot?

[Joel Eade]

Just playing devil's advocate, you can continuously adjust focus with your index finger and shoot too.



Extending the devil's advocate, this is probably a rare thing, so why "work" for 85-95% of your shots to mimic One Shot when you could instead remap AF-ON to be an AF-OFF button for that 5-15% of your shots to mimic One Shot?

It's easier (for me) when I am tracking birds in flight to intermittently "bump" the focus with my thumb or hold the button down with my thumb and shoot when the time is right with my index finger rather than try to constantly re-adjust with a half shutter press. Also it really isn't any extra work to focus on a relatively stationary object, like a perched bird, using your thumb and then re-compose the shot in the frame before firing the shutter. Using the back button focus this way I can stay ready for both stationary and flight shots all the time. I was skeptical too but I suggest you try it for awhile. I was pleasantly surprised how easy it was to get used to and how natural it feels.

[neuroanatomist]

Just playing devil's advocate, you can continuously adjust focus with your index finger and shoot too.

Extending the devil's advocate, this is probably a rare thing, so why "work" for 85-95% of your shots to mimic One Shot when you could instead remap AF-ON to be an AF-OFF button for that 5-15% of your shots to mimic One Shot?

I 'prefocus' a lot. For perched birds, portraits, and other subjects where the distance isn't changing but I want to capture a key moment/expression, traditional BBF works better, IMO. I can relax and wait for the moment, then just press the shutter. I don't want the delay the AF step would impart. With AF-STOP, I'd have to continually hold the button while waiting for the shot (or press it just before the shot, but why?).

I suppose either would work, once one got used to it. But for the reasons above, as well as Joel's statements, I find AF-ON preferable.