X-T20 Back Button Focus

[betty]

I love my Fuji X-T20 but as a beginner to ‘real’ photography I am on a learning journey.

 

As suggested on various internet sites, I have set my camera up for Back Button Focus and am trying to get used to it.

Please could someone clarify one thing for me? Does the focus lock when the BBF button is pressed once or do I have to hold it down all the time before pressing the shutter button?

 

I have done some sample shots and it would appear to hold the focus but the AFL label only shows on the screen when I hold the BBF button down. 

 

I have tried with main focus set to both S & C

 

What would be your advice re BBF? Thanks

[anhsnaps]

I love my Fuji X-T20 but as a beginner to ‘real’ photography I am on a learning journey.

As suggested on various internet sites, I have set my camera up for Back Button Focus and am trying to get used to it.

Please could someone clarify one thing for me? Does the focus lock when the BBF button is pressed once or do I have to hold it down all the time before pressing the shutter button?

I have done some sample shots and it would appear to hold the focus but the AFL label only shows on the screen when I hold the BBF button down.

I have tried with main focus set to both S & C

What would be your advice re BBF? Thanks

You should only have to press it once if in single focus.

 

 

Sent from my iPhone using Tapatalk

[Doug Pardee]

Does the focus lock when the BBF button is pressed once or do I have to hold it down all the time before pressing the shutter button?

 

For an actual "Lock," you need to keep the button pressed down. If you let up, AF simply stops, leaving the lens focused wherever it's focused, but focus is unlocked so you can manually focus if you want.

 

Be aware that if you're using AF-C, "wherever it's focused" is quite possibly not at the distance you want it to be focused, especially if the camera is using contrast-detect AF.

 

My advice for BBF: don't use it -- unless you really need to -- on Fuji (and possibly other mirrorless cameras). Contrast-detect auto-focus causes complications that don't affect DSLRs. Also... on a DSLR, the viewfinder, autofocus, metering, and image capture are four separate subsystems. In a mirrorless, they're all run off of the imaging sensor, and the camera generally prefers that everything be controlled by the shutter release button to make it simpler to control the sensor configuration.

[betty]

Thanks for the advice. 

[EdricBF]

BBF in DSLRs is great (I have a Nikon D750), but I never managed to really trust it in my mirrorless cameras (Panas, Olys and Fujis) for the reasons well pointed out above... 

[bbawt]

Interesting comments on advising not to use it, or not trusting it with contrast detect AF. So far I've been using BBF on my X-T20 without an issue - seems to work just like my D7100 does. My only initial problem was forgetting to de-couple my shutter button focus when I assigned AF to the AE-L button.

 

Anyone have any sources that explain the risks of using BBF on mirrorless cameras?

 

For an actual "Lock," you need to keep the button pressed down. If you let up, AF simply stops, leaving the lens focused wherever it's focused, but focus is unlocked so you can manually focus if you want.

 

Be aware that if you're using AF-C, "wherever it's focused" is quite possibly not at the distance you want it to be focused, especially if the camera is using contrast-detect AF.

 

My advice for BBF: don't use it -- unless you really need to -- on Fuji (and possibly other mirrorless cameras). Contrast-detect auto-focus causes complications that don't affect DSLRs. Also... on a DSLR, the viewfinder, autofocus, metering, and image capture are four separate subsystems. In a mirrorless, they're all run off of the imaging sensor, and the camera generally prefers that everything be controlled by the shutter release button to make it simpler to control the sensor configuration.