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Occasional Contributor
Posts: 7
Registered: ‎05-11-2016
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AI Servo AF and Backbutton Focus T6i

I have my Canon T6i set up for back button focus using single-point AF mode. I would like to photograph birds. If I set the camera to AI Servo AF and use the back button to focus on the bird and the bird takes off, will the camera stay focused on the bird as it moves across the frame in the same manner that the manual describes when using the shutter button for both exposure and focus (the default)

Honored Contributor
Posts: 7,861
Registered: ‎08-13-2015

Re: AI Servo AF and Backbutton Focus T6i


@vic6 wrote:

I have my Canon T6i set up for back button focus using single-point AF mode. I would like to photograph birds. If I set the camera to AI Servo AF and use the back button to focus on the bird and the bird takes off, will the camera stay focused on the bird as it moves across the frame in the same manner that the manual describes when using the shutter button for both exposure and focus (the default)


Which shooting mode are you using?  You definitely want to use one of the Creative modes like Av, Tv, or M.  Ideally, you will also want a FAST shutter speed, which Creative modes are capable of providing. 

 

Controlling auto focus is a multi-faceted task.  You have to select a focusing mode, One Shot or AI Servo.  You have to select an AF point, usually the center AF point is best because it is the most sensitive. But, you can also enable multiple AF points.

 

An example of all AF points being enabled is Green [A] mode, which automatically selects an AF point for you.  It displays a group of AF points that are capable of locking focus under whatever the AF points is covering.  However, the camera will only use one of the lit AF points to actually focus the lens.  In most cases, the camera will lock focus with the AF point covering the closest object to the camera.  You have NO CONTROL over which AF point it will use.  This is why people like to use Creative modes like P mode, which allows you select the AF point

 

When you use AI Servo, most people want all AF points enabled,  Enabling multiple points allows the camera to track a subject by switching from one AF point to another as the subject moves around the frame.  The trick is that you want to tell the camera to always begin tracking with the center AF point.

 

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Esteemed Contributor
Posts: 4,889
Registered: ‎06-25-2014

Re: AI Servo AF and Backbutton Focus T6i


@vic6 wrote:

I have my Canon T6i set up for back button focus using single-point AF mode. I would like to photograph birds. If I set the camera to AI Servo AF and use the back button to focus on the bird and the bird takes off, will the camera stay focused on the bird as it moves across the frame in the same manner that the manual describes when using the shutter button for both exposure and focus (the default)


I think it will track the bird just as the shutter button would have, as long as you hold the back button down. But remember to disable the shutter button's focusing functionality; you don't want the two buttons fighting for control.

Bob
Philadelphia, Pennsylvania USA
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