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Occasional Contributor
Posts: 14
Registered: ‎11-09-2018

Canon 5d mk4 back button Focus and AI servo/One shot.

If you decide to enable back button focus by decoupling it from the shutter button as I have, why do you need to switch from AI Servo to One Shot. Surely BB focus provides both options. Holding BB focus is effectively giving you AI Servo, releaseing the button gives you One Shot.

Valued Contributor
Posts: 365
Registered: ‎10-21-2016

Re: Canon 5d mk4 back button Focus and AI servo/One shot.

It sounds more like you have set the back button to switch between one shot & AI focus.

Have you taken the focus off of the shutter button ?

VIP
Posts: 8,163
Registered: ‎08-13-2015

Re: Canon 5d mk4 back button Focus and AI servo/One shot.

One Shot mode will focus faster than a short tap in SI Servo mode. Plus, I think Spot AF is only available in One Shot.
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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
Occasional Contributor
Posts: 14
Registered: ‎11-09-2018

Re: Canon 5d mk4 back button Focus and AI servo/One shot.

If you decide to enable back button focus by decoupling it from the shutter button "as I have",


@Ray-uk wrote:

It sounds more like you have set the back button to switch between one shot & AI focus.

Have you taken the focus off of the shutter button ?


 

Valued Contributor
Posts: 365
Registered: ‎10-21-2016

Re: Canon 5d mk4 back button Focus and AI servo/One shot.


@yosser29 wrote:

If you decide to enable back button focus by decoupling it from the shutter button "as I have",


@Ray-uk wrote:

It sounds more like you have set the back button to switch between one shot & AI focus.

Have you taken the focus off of the shutter button ?


 


I asked you the question because a lot of people don't realise that you have to change 2 options to get proper BBF.

1. You have to enable focus on the back button.

Then ........

2. You have to disable focus on the shutter button.

 

If you don't do the latter then you will find that if you preset the focus with the back button then release that button, when you press the shutter button it will focus again.

Esteemed Contributor
Posts: 4,981
Registered: ‎06-25-2014

Re: Canon 5d mk4 back button Focus and AI servo/One shot.


@yosser29 wrote:

If you decide to enable back button focus by decoupling it from the shutter button as I have, why do you need to switch from AI Servo to One Shot. Surely BB focus provides both options. Holding BB focus is effectively giving you AI Servo, releaseing the button gives you One Shot.


Are you sure? I don't have time to look it up just now, but I was under the impression that BB focus with the shutter button decoupled simply assigned the back button the focusing functionality that the shutter button would have had. And in one-shot mode that means freezing the focus at its current value. Ony in AF Servo mode would it allow the focus to keep changing.

Bob
Philadelphia, Pennsylvania USA
Occasional Contributor
Posts: 14
Registered: ‎11-09-2018

Re: Canon 5d mk4 back button Focus and AI servo/One shot.

No I am not sure but convinced my changes are proding the same results. To reiterate I have decoupled focus from the shutter button which now only performs the metering and shutter activation. I have the AF on button working as back button focus. Holding down the AF on button causes the camera to act the same as AI servo ie constantly focusing nothing else. Releasing this button causes focusing to stop in effect exactly the same as ONE SHOT and holds that focus. Firing the shutter does not affect focus because focusing is not activated by the shutter. It definitely works benn using it for months.
Valued Contributor
Posts: 365
Registered: ‎10-21-2016

Re: Canon 5d mk4 back button Focus and AI servo/One shot.

Ahh ... your latest explanation makes it much clearer.

 

You have AI servo enabled permanently.

You use back button to start AI servo.

You release back button when it has found focus.

 

Strictly speaking this not one-shot although I can see that it would probably work most of the time.

 

The two disadvantages that I can see is that you get no focus confirmation and it is technically possible that you could release the back button and turn off focusing whilst the AI focus is in the transition between 2 different focus positions.

I think by doing this you would also be negating the advantage of the focus / shutter priority setting.

Occasional Contributor
Posts: 14
Registered: ‎11-09-2018

Re: Canon 5d mk4 back button Focus and AI servo/One shot.

Exactly as you describe, really should have mentioned the submenu to activate AI Servo when using AF on as back button focus. My error there, nevertheless appears to work perfectly for me. Thanks for your input. 

 

VIP
Posts: 8,163
Registered: ‎08-13-2015

Re: Canon 5d mk4 back button Focus and AI servo/One shot.


@yosser29 wrote:

Exactly as you describe, really should have mentioned the submenu to activate AI Servo when using AF on as back button focus. My error there, nevertheless appears to work perfectly for me. Thanks for your input. 

 


It might feel the same for 99% of shots, but it really is not.  Besides, you really do not get a focus confirmation.  Although you can set 1st Image Priority to full Focus Priority, there is no guarantee you have locked focus when using BBF like that.  This approach works for nearly any casual shooting situation.  But, it can and will come up short when critical focus is top priority.

 

Depending upon how you have the AF tracking parameters set, briefly activating AI Servo with BBF is most definitely slower to lock focus than using One Shot mode.  I found this out when trying to focus on a bird sittting on a tree branch surrounded by many other branches.  

 

AF tracking needs to be “dumbed down” so that it stays with the current AF point, is slower to switch AF points, etc.  If you are not using the center AF point as your starting point for tracking then it will definitely be slower to lock focus.  

 

Even when it locks, it will immediately begin to “creep” as it attempts to track a moving subject that is probably not moving around.  When this happens you must start over, and reacqure focus.

 

On the other hand, One Shot mode will lock focus, STOP refocusing, and stay put.  AI Servo does the exact opposite.  It will keep refocusing until you lift your finger off of BBF.  You are better off just keeping your finger pressed on the BBF, so that you can guarantee yourself that your shutter will fire when critical focus is reached.  Of course, this assumes that you have set 1st Image Priority to full Focus Priority.

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