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FORUMS Canon Cameras, Lenses & Accessories Canon EOS Digital Cameras 
Thread started 18 Dec 2017 (Monday) 15:37
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Back button focus

 
Nascar ­ Nut
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Dec 19, 2017 14:57 |  #16

apersson850 wrote in post #18521584 (external link)
No, the trigger button will not "focus as well". Since you are already holding the AF-ON pressed, the camera's autofocus is active. It can't do any more than that. It can't be active-active. Thus you'll not notice any difference.
But it looks like you have set AF-ON to also switch to Servo AF when held. And if so, then that setting does have priority, so as long as you keep AF-ON pressed, then Servo AF it is.

However, if you release the AF-ON button and have focus active on the trigger button, then you get all that others have already commented about.

Now this is how I was thinking it was. Cyberdyne is saying the opisite as is the person who got me thinking about it and lead me to my post.




  
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DaviSto
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Dec 19, 2017 15:12 |  #17

Nascar Nut wrote in post #18521935 (external link)
Now this is how I was thinking it was. Cyberdyne is saying the opisite as is the person who got me thinking about it and lead me to my post.

If you are using AI Servo mode the the camera will adjust focus all the while you have the back button pressed. As soon as you stop pressing the back button ... AF will stop ... and if you have separated focus from the shutter release, the plane of focus will remain the same when you take the shot.

If you haven't taken AF off the shutter release, the camera will adjust focus again when you press the shutter release ... meaning that you are not really using the back button to control focus.

If you keep the back button pressed right up to the point when the shutter release is pressed, it is true that there will be no additional focus action as a result of pressing the shutter release. But what difference does that actually make? The camera has been continuously adjusting focus right up to the instant of taking the shot, anyway.

In effect, if focusing is not separated from the shutter release, depressing the shutter release will always determine focus ... so there is no point whatsoever in using BBF if this is the case.


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Charlie
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Dec 19, 2017 15:36 |  #18

I dont recall if Canon bodies have the feature, but a disable AF button, I've been using rather than BBAF for the same reasons, I can pass the camera to anyone to take a snap for me. Especially helpful at weddings where I'm a simple guest that wants high quality images since my family is dressed to impress. For normal shooting, I can press the focus disable button, and it works like BBAF, but opposite, I use shutter button and simply decouple AF by holding a custom button rather than releasing the custom button.


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Post edited 7 months ago by Wilt. (4 edits in all)
     
Dec 19, 2017 15:54 |  #19

Charlie wrote in post #18521978 (external link)
I dont recall if Canon bodies have the feature, but a disable AF button, I've been using rather than BBAF for the same reasons, I can pass the camera to anyone to take a snap for me. Especially helpful at weddings where I'm a simple guest that wants high quality images since my family is dressed to impress. For normal shooting, I can press the focus disable button, and it works like BBAF, but opposite, I use shutter button and simply decouple AF by holding a custom button rather than releasing the custom button.

That is the button on the Canon lens controlling AF function, position that is labeled 'MF'. Sigma, Tokina, and Tamron all have similar functional control on the lens.


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Dec 19, 2017 15:54 |  #20

apersson850 wrote in post #18521584 (external link)
No, the trigger button will not "focus as well". Since you are already holding the AF-ON pressed, the camera's autofocus is active. It can't do any more than that. It can't be active-active. Thus you'll not notice any difference.
But it looks like you have set AF-ON to also switch to Servo AF when held. And if so, then that setting does have priority, so as long as you keep AF-ON pressed, then Servo AF it is.

However, if you release the AF-ON button and have focus active on the trigger button, then you get all that others have already commented about.

What's a "trigger" button?


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Tom ­ Reichner
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Dec 19, 2017 16:30 |  #21

.

Archibald wrote in post #18521995 (external link)
What's a "trigger" button?

I'm not really sure.

Perhaps apersson850 meant to say "shutter button". . That's the only thing I can think of that would make any sense.


.

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CyberDyneSystems
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Post edited 7 months ago by CyberDyneSystems. (4 edits in all)
     
Dec 19, 2017 16:31 |  #22

CyberDyneSystems wrote in post #18521122 (external link)
The problem with your set up is that yes, the Shutter will try to focus.

One of the advantages of BBF is being able to let go of the AF, so the lens won't try to refocus when you activate the shutter.


Nascar Nut wrote in post #18521935 (external link)
Now this is how I was thinking it was. Cyberdyne is saying the opisite as is the person who got me thinking about it and lead me to my post.

Perhaps I misunderstood your question, but i don't think I am saying the opposite. The 2nd half of my reply should clarify the important part, and remains true.

My point is that if you don't remove AF from the shutter button, you can't get the full, in fact the main advantage of BBF.

I am in full agreement with the fact that if AF is already active, if you already have your thumb on the AF ON button, then pressing another button to activate the already active AF will have no effect, negative or otherwise. At the same time, doing this you would also get the same result by not bothering to use your thumb at all. End result is identical to the standard out of the box set up of using shutter half press to activate AF.


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Post edited 7 months ago by CyberDyneSystems. (2 edits in all)
     
Dec 19, 2017 16:34 |  #23

Archibald wrote in post #18521995 (external link)
What's a "trigger" button?

Tom Reichner wrote in post #18522022 (external link)
.I'm not really sure.
Perhaps apersson850 meant to say "shutter button". . That's the only thing I can think of that would make any sense.
.
.

I don't think apersson850 and I are the only ones that say "trigger the shutter" truly? It appears to be very common parlance.


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Post edited 7 months ago by CyberDyneSystems.
     
Dec 19, 2017 16:40 |  #24

CyberDyneSystems wrote in post #18522024 (external link)
My point is that if you don't remove AF from the shutter button, you can't get the full, in fact the main advantage of BBF.

Exactly.


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Post edited 7 months ago by Charlie. (2 edits in all)
     
Dec 19, 2017 16:42 |  #25

Wilt wrote in post #18521994 (external link)
That is the button on the Canon lens controlling AF function, position that is labeled 'MF'. Sigma, Tokina, and Tamron all have similar functional control on the lens.

uhh, no.

it's called focus hold, it disables AF while the button is pressed, and re-enabled when let go. Like BBAF but opposite in function.

EDIT: Lens AF-Stop, but on a custom button rather than the lens.


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Dec 19, 2017 16:44 |  #26

Charlie wrote in post #18522034 (external link)
uhh, no.

it's called focus hold, it disables AF while the button is pressed, and re-enabled when let go. Like BBAF but opposite in function.


:) "Badass"

https://www.youtube.co​m/watch?v=fhm-rdFQSQE (external link)

If it's on the lens like this, then Wilt is correct that it's on most Canon telephotos, (likewise it's not on all Sony lenses) It has been on Canon lenses since the 1990s.

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Dec 19, 2017 16:50 |  #27

CyberDyneSystems wrote in post #18522035 (external link)
:) "Badass"

https://www.youtube.co​m/watch?v=fhm-rdFQSQE (external link)

If it's on the lens like this, then Wilt is correct that it's on some Canon telephotos, has been since the 1990s.

:lol:

yes that's it. I understood it, but never gave it a chance, till recently..... and I like it.

I knew canon had that extra button for something :-P


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Dec 19, 2017 16:52 |  #28

Charlie wrote in post #18522034 (external link)
uhh, no.

it's called focus hold, it disables AF while the button is pressed, and re-enabled when let go. Like BBAF but opposite in function.

EDIT: Lens AF-Stop, but on a custom button rather than the lens.
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You mean like stopping pressing the assigned BBF button??? I'm not sure why you need another button as well. A button is a binary thing .. it's 'on' or 'off'. An opposite button is also a binary thing ... it's 'off' or 'on'.

I know I am missing something here but I need more explanation and information to understand what it is.


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Dec 19, 2017 16:53 |  #29

So Charlie, you can assign the function to a button on the body as well?

I guess I am not surprised as SONY let's you assign pretty much any button anywhere!!:)


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Dec 19, 2017 16:56 |  #30

DaviSto wrote in post #18522051 (external link)
You mean like stopping pressing the assigned BBF button??? I'm not sure why you need another button as well. A button is a binary thing .. it's 'on' or 'off'. An opposite button is also a binary thing ... it's 'off' or 'on'.

I know I am missing something here but I need more explanation and information to understand what it is.


This is just a preference thing. Functionally you are right, no difference.

I know some birders that excel at birds in flight, (like some of the best in the game) that leave AF on the shutter and use the AF stop button instead. It is not limiting to them as they ALWAYS have a Canon supertelephoto with the AF stop button equipped.

It was never my preference, but operationally, it's just a matter of what you get used to. It's instead of BBF, not in addition to.


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