# AF Modes, Why not AI Focus as default?



## SuzukiGS750EZ (Oct 10, 2016)

Hey guys! I've always wondered this: Why don't people just set AF to AI Focus. It's supposed to be a mix of One Shot and AI Servo, so why not the best of both worlds? I honestly haven't been all that impressed with AI Focus, at sporting events i chose AI Servo and everything else i do one shot. Where is the advantage of AI Focus and how do you get it to work properly?


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## robbins.photo (Oct 10, 2016)

SuzukiGS750EZ said:


> Hey guys! I've always wondered this: Why don't people just set AF to AI Focus. It's supposed to be a mix of One Shot and AI Servo, so why not the best of both worlds? I honestly haven't been all that impressed with AI Focus, at sporting events i chose AI Servo and everything else i do one shot. Where is the advantage of AI Focus and how do you get it to work properly?


Well not a canon shooter but my guess is it probably works somewhat similar to a Nikon setting where the camera guesses as to which mode you want based on the scene.

This will invariably lead to the camera making the wrong choice usually at the worst time.

On my Nikon I always shoot afs-c, which I believe is the same as ai servo on the Canon.  If I get an extra frame or two that wasn't intended it really doesn't matter, I can always go back and delete them later

Sent from my N9518 using Tapatalk


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## SuzukiGS750EZ (Oct 10, 2016)

Through my searches and video watching last night, I realized I can set the back button AF and have the ai focus set to ai servo. Then it will focus one shot if pressed or continuous if held. Best of both worlds.


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## robbins.photo (Oct 10, 2016)

SuzukiGS750EZ said:


> Through my searches and video watching last night, I realized I can set the back button AF and have the ai focus set to ai servo. Then it will focus one shot if pressed or continuous if held. Best of both worlds.



A lot of folks swear by back button focus.. me I found it to be more complicated than what it was worth, just never could quite get the hang of it.  So I just leave it in AFS-C mode, if I get a couple of extra shots because I'm too slow laying off the shutter, eh.. doesn't really matter.  I've never come close to filling my memory cards anyway.


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## SuzukiGS750EZ (Oct 10, 2016)

I just have to make it a habit to hit that button and not the shutter button like i'm used to. But once i start using it throughout the day i haven't forgotten. Just the first time i go to shoot and i do the "is my camera on..." look when i hold the shutter button down.


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## DarkShadow (Oct 10, 2016)

Or better yet back button focus tap and let go one shot no need to have the AF-restart for each shot.Hold down for continues focus works like a charm. It may seem weird at first but after you get used to its a wonderful feature.


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## TCampbell (Oct 11, 2016)

If focus algorithm changes depending on if the camera expects a subject to be moving.  This is because AI Servo focus (continuous focus) is "predictive" ... meaning if a subject appears to have gotten closer then the algorithm can believe the subject will continually move in that same direction and will change focus to where it thinks the subject will be next... and miss focus because the subject wasn't really moving to that spot.   Give it a moment and it will realize it's mistake and refocus accurately, but if you happen to press the shutter button at the wrong time... you can miss the shot.    

So if you KNOW the subject _is not_ moving, it's always better to use "One Shot" mode.  If you KNOW the subject _is_ moving it's better to use AI Servo focus.  

"AI Focus" is a mode in which the computer tries to determine which focus mode should be better for the shot.  The downside is that it takes the computer a moment to decide which focus mode to use (a fractional delay) and if YOU know if the subject is moving or not and set the mode ahead of time (instead of letting the camera figure it out) then you'll get faster focusing performance.


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