What happens when I release the focus button?

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GuyBooth

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I am struggling with this statement in Steve's book on Autofocus:
"As long as you maintain a half-press on the shutter release, the system will​
hold that focus distance for you. It only resets and refocuses when your​
finger disengages from the half-press."​

I use back button focusing, and for many years have assumed that I can release the button once I have achieved focus (we're not talking about moving subjects here).
Steve's statement seems to say that if I release the focus button, the camera will refocus - but why would it? What would it refocus on? I'm not telling it to refocus, so why wouldn't the camera stay focused at the same place I focused on originally?

If I would have thought this was true:
"It only resets and refocuses when your​
finger reengages with another half press"​

BUT that's not what he says. Does anyone have any insight? It makes a big difference in how I take my photos ...
 
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Many of us have Steve's eBooks. What page are you referencing?

Steve appears to be addressing focusing with the shutter release, not the AF-On button. When using AF-On focusing, the shutter release is disconnected from focusing.
 
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Butlerkid said:
Steve appears to be addressing focusing with the shutter release, not the AF-On button. When using AF-On focusing, the shutter release is disconnected from focusing.
Click to expand...
Yes I understand that - but my understanding is that the action of pressing and releasing the AF-On button when it is set up for BBF is identical to the focusing action of half-pressing the Shutter Release. If so, I am assuming his statement could be re-written as :
"As long as you keep the AF-On button depressed, the system will​
hold that focus distance for you. It only resets and refocuses when your​
finger releases the AF-On button."​
And this is what I am questioning.
 
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Read his statement again. Maintain half pressure on the "SHUTTER RELEASE" he is talking about the shutter button not the BBF. If you have set up in menu for the shutter to just release and all focus to be performed by the BBF, a half press of the shutter release does nothing. In your cameras menu, under Autofocus - Autofocus activation should be set to "OFF" reflecting AF-ON Only. If not set to OFF it is then set to Shutter/AF-On where presing the shutter button will refocus whether or not you used BBF.
 
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GuyBooth said:
Yes I understand that - but my understanding is that the action of pressing and releasing the AF-On button when it is set up for BBF is identical to the focusing action of half-pressing the Shutter Release. If so, I am assuming his statement could be re-written as :
"As long as you keep the AF-On button depressed, the system will​
hold that focus distance for you. It only resets and refocuses when your​
finger releases the AF-On button."​
And this is what I am questioning.
Click to expand...

Nope! With BBF set up releasing the AF-on button LOCKS the focus, it does nothing else until you press it again.
 
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dabhand16 said:
Nope! With BBF set up releasing the AF-on button LOCKS the focus, it does nothing else until you press it again.
Click to expand...
Is this explained anywhere (in the Nikon manual, for example)? This is certainly the way I have been using it all this time, and it seems to have been OK but my focus needs have usually not been super-critical.
I also assume that however it works with the AF-On button will be the way it works if I have the Fn1 button programmed the same way.
 
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Both the OP's comments and Karen's comments are correct. Once the camera is set to use back button focusing (BBF) the focusing can be disengaged from the shutter button. That way the camera focuses when the AF-On button is pressed and then maintains and locks in the last focus distance when the button is released. That way you can stop focusing once you've achieved focus on a stationary subject and just keep shooting. There is one caveat to this though - it is possible to enable both the back button and the shutter to drive focus alternatively at the same time. There are two steps to set up BBF. First is to use the menu to enable the back button to focus, and second is to also use the menu settings to disengage focus from the shutter button. My wife's Z50 is set up to focus using the shutter button the way she prefers, and I've also enabled the AF-On button for me to use when I use the camera. In that case the BBF overrides the shutter autofocusing as long as I keep the AF-On button pressed. With my wife not touching the AF-On button when she shoots the shutter button does the focusing.
 
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To answer Karen's earlier question:
Secrets To The Nikon Autofocus System: Mirrorless Edition, Page 24.
JohnW said:
In your cameras menu, under Autofocus - Autofocus activation should be set to "OFF" reflecting AF-ON Only. If not set to OFF it is then set to Shutter/AF-On where pressing the shutter button will refocus whether or not you used BBF.
Click to expand...
Just to clarify - my Autofocus IS set to OFF.
Thanks everyone - Rassie sums it up for me nicely:
"That way the camera focuses when the AF-On button is pressed and then maintains the last focus distance when the button is released. That way you can stop focusing once you've achieved focus on a stationary subject and just keep shooting."​
 
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GuyBooth said:
"As long as you keep the AF-On button depressed, the system will
hold that focus distance for you. It only resets and refocuses when your​
finger releases the AF-On button."​
And this is what I am questioning.
Click to expand...
When you press the AF-On button In AF-S mode the camera achieves and immediately locks focus. It will not re-focus until you release and press the button again. Once focus has been achieved in AF-S mode there is no further use in keeping the button depressed.
In AF-C mode the camera will continuously keep refocusing as long as the AF-On button is depressed. Once the button is released the focus is locked at the last focus position and is re-activated on a new press of the button.
 
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In AF-C

Once you press the AF-on when set up for BBF, the camera maintains that focus point even after pressing the shutter release. If you don't re-engage the AF-On it will hold the original focus point even after shutter release.

Shutter button if AF Activation set to ON once half press it acquires focus and will stay focused on that same point until you release pressure. If you hold the shutter button down you can take multiple images but the focus remains on the point where you originally acquired focus. Lot of us use to use this prior to BBF, Focus and then recompose.

The AF-On does not react the same as the shutter release. Where constant 1/2 pressure lock focus on the acquired focus point, with AF-on a single press locks focus on the acquired focus point. If the subject is static whether you single press AF-On or keep constant pressure on the AF-On button makes no difference focus is locked and hit shutter to take the image.

However if the image is not static, keeping the AF-On pressed will follow the subject and retain focus on the subject, where if you had only pressed AF-On to initially acquire focus any movement would render the image out of focus, as focus is still on the initial acquired point.
 
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GuyBooth said:
Yes I understand that - but my understanding is that the action of pressing and releasing the AF-On button when it is set up for BBF is identical to the focusing action of half-pressing the Shutter Release. If so, I am assuming his statement could be re-written as :
"As long as you keep the AF-On button depressed, the system will​
hold that focus distance for you. It only resets and refocuses when your​
finger releases the AF-On button."​
And this is what I am questioning.
Click to expand...
I believe your rewrite would be true if you were in af-s mode. But BBF setup assumes you are in af-c mode.at all times. In bbf autofocus keeps adjusting while the button is pressed but disengages completely and stays locked at that focus when you release the back button.
 
If you have a mirrorless camera there are other alternatives to bbf and maybe that is what the book was discussing?
 
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GuyBooth said:
I am struggling with this statement in Steve's book on Autofocus:
"As long as you maintain a half-press on the shutter release, the system will​
hold that focus distance for you. It only resets and refocuses when your​
finger disengages from the half-press."​

I use back button focusing, and for many years have assumed that I can release the button once I have achieved focus (we're not talking about moving subjects here).
Steve's statement seems to say that if I release the focus button, the camera will refocus - but why would it? What would it refocus on? I'm not telling it to refocus, so why wouldn't the camera stay focused at the same place I focused on originally?

If I would have thought this was true:
"It only resets and refocuses when your​
finger reengages with another half press"​

BUT that's not what he says. Does anyone have any insight? It makes a big difference in how I take my photos ...
Click to expand...

“The default behavior of this mode is to allow you to release the shutter ONLY if focus has been achieved and locked in (called Focus Priority). However, if you maintain a half-press of the shutter release once you have a lock, you can still recompose and shoot - even if what’s under the AF point is no longer in focus. On the other hand, if you have not achieved a focus lock, you can press that shutter all you want but the camera will refuse to fire.” Everything on pg 24 of edition 1.3 refers to single servo AF. His point is that AF-S is made for stationary objects.

Steve is referring to AF-S using the shutter release. So what he means is that if you don’t get a lock the shutter will not fire when you press the shutter. The purpose of AF-S is to only allow a shutter release after focus has been achieved . He’s not referring to BBF while in continuous mode. Once you release the shutter you have to refocus to get a lock By half pressing the shutter again.
BBF is used with continuous focus, so once you establish focus on a stationary object you can release the BBF button and the focus at that distance will be maintained.
 
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bleirer said:
If you have a mirrorless camera there are other alternatives to bbf and maybe that is what the book was discussing?
Click to expand...

Not sure what you are referring to here. If you want autofocus, the only alternative to BBAF is shutter release AF. If you don't necessarily want AF, manual focus is always available.

My Fuji XT-2 and XT- 4 are both set up for BBAF but I can switch to manual focus at the touch of a switch. The default is for shutter release AF though.
 
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bleirer said:
The mirrorless book is the one the OP says they are using.
Click to expand...
Thanks for the clarification. I just read pg. 24 in the mirrorless book and it is pretty much giving the same exact explanation As I referred to above. It’s referring to single shot servo not BBF.

"As long as you maintain a half-press on the shutter release, the system will
hold that focus distance for you. It only resets and refocuses when your
finger disengages from the half-press.”

The statement above from Steve’s book that Guy quotes:
refers to Single Shot Servo not BBAF. The purpose of AF-S is to only allow a shutter release after focus has been achieved . Steve is not referring to BBAF while in continuous mode.
 
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dabhand16 said:
Not sure what you are referring to here. If you want autofocus, the only alternative to BBAF is shutter release AF. If you don't necessarily want AF, manual focus is always available.

My Fuji XT-2 and XT- 4 are both set up for BBAF but I can switch to manual focus at the touch of a switch. The default is for shutter release AF though.
Click to expand...
I'm referring to bleirer's comment thus " If you have a mirrorless camera there are other alternatives to bbf and maybe that is what the book was discussing? "

I know exactly how to use either method of invoking the AF system but was intrigued that someone felt there was an alternative. Let's see.
 
gbodave said:
BBAF works just the same on my Sony A9 as on a DSLR.

Bleirer : What are the alternatives to BBAF on mirrorless please.
Click to expand...
I think I will start a new topic for that, so I don't hijack this one.
 
bleirer said:
I think I will start a new topic for that, so I don't hijack this one.
Click to expand...

BBAF Alternatives for Mirrorless

I shoot Canon, but the idea is the same for all brands. Instead of the usual bbaf setup I use this alternative for mirrorless and find several advantages. It wasn't my idea. I first saw it on a youtube video and Steve covered the idea. I keep the focus mode on servo/continuous at all times...
bcgforums.com bcgforums.com
 
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I finally found the appropriate comment in Steve's book on page 57:
"As long as you keep your finger OFF of the AF-On button, the lens won’t​
refocus, effectively keeping it “locked in” at whatever distance it was the​
last time you pressed AF-On."​
So much information to absorb. :)
 
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Some of this discussion illustrates why several years back before mirrorless and after a bit over a year I quit using back button and went back to the simplicity of AF-C and shutter release button half press focus it is simple and very effective and used for 95% of what I shoot. It also frees up my thumb to move my focus point to where I want it and as @Steve has pointed out that is all over the view finder/sensor in a mirrorless ... one of the things I really like about my wife's Z50.
 
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