Use of AF-on

[photoguy12]

Fellow photographers:

I am curious as to when to use the "AF-on" button on my Canon 7D. I have always used the shutter button to initiate focus. I'm sure the button is there for a reason, I just can't figure it out. Thanks for any assistance.

Photoguy12

[plasticmotif]

To be used to focus the camera, via custom functions, then use the shutter button to take the picture.

[ReconCadre]

there was a post in dpreview regarding this

I've never really understood the use case for the AF ON button, but I shot a soccer game recently and it finally made sense. If you've never understood the usefulness of the AF ON button, then this post might be for you.

Sports photography is new to me. For years, I had happily used the half-pressed shutter button on the rare occasions when I was in AI Servo mode. For soccer, that worked great for tracking a player and firing a single burst. I am not nimble enough to release the shutter button back to the half-pressed point, so when the burst ended I inevitably released the shutter button all the way.

That caused AI Servo to stop. When I wanted to fire off a few shots in quick succession but with pauses in between, I realized that I often couldn't reacquire the "right" player. That's when it hit me. Find my player, press and hold AF ON through the series of shots. That allows AI Servo to track the same player and avoids any focus lag when trying to take the next group in the series. To acquire a different player, release AF ON, center on that player, and press AF ON again. Rinse and repeat.
Duh! I've heard a variety of explanations, but they never really clicked.
I can only find one sentence about the AF ON button in the 7D manual. It deserves a full page.

Happy shooting!



read more about AF
http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=3049

[apersson850]

It's when using Servo AF the AF-ON button excels. You can also use it to temporarily stop tracking, if some obstacle enters the scene.
Another trick (on the 7D) is to set AF-ON to focus with the selected AF point, but use * for a pre-registered point (HP; Home Point).

[davethejnz]

On the same subject of the AF-ON button, can some please explain to in simple understandable point form how to set up my 7D so that

AF and metering is obtained by using the AF-ON Button and the shutter button is ONLY used to take the shot. AE lock can still be obtained by using "*" if required

I mainly shoot sport (or moving objects) in AI Servo mode. I have read the manual over and over again pg 217 and pg 218 and for the life of me cannot understand how to achieve what I want.

Thanks in advance

[Ade H]

I use it as AF-off, via the custom function (40D). I like that for preventing focussing after using FTM. I tried taking AF away from the shutter release (which would achieve the same effect as it happens) and using AF-on in the default way, but that just didn't suit. It gave me no advantage (can be different for other folk, of course) and got in the way of quick shots.

[LibertyToad]

I use it as AF-off, via the custom function (40D). I like that for preventing focussing after using FTM. I tried taking AF away from the shutter release (which would achieve the same effect as it happens) and using AF-on in the default way, but that just didn't suit. It gave me no advantage (can be different for other folk, of course) and got in the way of quick shots.

I have mine set up the same way. I can lock focus when I want otherwise focus is triggered from the shutter. Handy.

[apersson850]

David, in C.Fn IV-1, you go to the shutter button and set that to metering. As a default, it's metering and focus.

If you haven't changed anything else, that's all it takes, as the AF-ON button is set to metering and focus from the beginning.

So you don't give AF and metering to AF-ON, you remove AF from the shutter button.

[davethejnz]

David, in C.Fn IV-1, you go to the shutter button and set that to metering. As a default, it's metering and focus.

If you haven't changed anything else, that's all it takes, as the AF-ON button is set to metering and focus from the beginning.

So you don't give AF and metering to AF-ON, you remove AF from the shutter button.

Thanks Anders

That's all I needed - a little help and now I am as happy as can be. I have changed a couple of other things but none in C.Fn IV.

Hopefully that will not effect anything. All seems to be working as it should.

[Replaces]

I've been using it today but my reach was so short this became really... useless
and when I'm using a grip trying to shoot vertically, pressing AF-ON button becomes a pain in the butt!
Is there a way to use AF-ON using grip without stretching my fingers super wide to press onto it -_-;?

[apersson850]

You can set the * button to do what the AF-ON button otherwise would have done. If your thumb has been cut off, so you can't reach the AF-ON button, that is.

[digital paradise]

there was a post in dpreview regarding this

I've never really understood the use case for the AF ON button, but I shot a soccer game recently and it finally made sense. If you've never understood the usefulness of the AF ON button, then this post might be for you.

Sports photography is new to me. For years, I had happily used the half-pressed shutter button on the rare occasions when I was in AI Servo mode. For soccer, that worked great for tracking a player and firing a single burst. I am not nimble enough to release the shutter button back to the half-pressed point, so when the burst ended I inevitably released the shutter button all the way.

That caused AI Servo to stop. When I wanted to fire off a few shots in quick succession but with pauses in between, I realized that I often couldn't reacquire the "right" player. That's when it hit me. Find my player, press and hold AF ON through the series of shots. That allows AI Servo to track the same player and avoids any focus lag when trying to take the next group in the series. To acquire a different player, release AF ON, center on that player, and press AF ON again. Rinse and repeat.
Duh! I've heard a variety of explanations, but they never really clicked.
I can only find one sentence about the AF ON button in the 7D manual. It deserves a full page.

Happy shooting!



read more about AF
http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=3049

That was a good explanation. I have never seen the value with it either however I'd am interested it exploring it. I do OK at sports events but you are correct as you have to reacquire the target. Another new thing for an old guy to learn.

[krb]

In addition to the soccer example, by removing AF from the shutter button you can get everything composed and focused just the way you want and have no worries that the camera is going to re-focus when you press the shutter button.

[davethejnz]

In addition to the soccer example, by removing AF from the shutter button you can get everything composed and focused just the way you want and have no worries that the camera is going to re-focus when you press the shutter button.

100% correct and this is why I use the AF-ON button in both AI Sevro and One Shot modes.

[Josh_30]

I've been using it today but my reach was so short this became really... useless
and when I'm using a grip trying to shoot vertically, pressing AF-ON button becomes a pain in the butt!
Is there a way to use AF-ON using grip without stretching my fingers super wide to press onto it -_-;?

Go into the CFn menu and turn on the af-on/* swap function. This effectively makes the * button into the af-on button so you can use back button focus on older grips without the af-on button. Works great on the 40D.