AF ON button - I finally get it

[brobar]

I see what it is doing now when you assign the ONE SHOT AI SERVO to the depth of field preview button. I was under the impression that a simple press and release of the button would switch/toggle the mode for you... but it is really a press and hold for a "temporary" switch while you are holding it... but upon release it goes right back to where it was before.

Not quite what I was expecting but I could see where it would be useful for some. It would be more usefull (for me) if it were a simple press and release of the button for a quick permanent switch of the mode until you press and released it again to switch back or changed it in settings.

Still cool though.
--
-Brock
A few of my images: http://www.brockbarnes.com

 

[dprsok]

I also decided not to use it, as it feels awkward to shoot while holding the button.

I see what it is doing now when you assign the ONE SHOT AI SERVO to the depth of field preview button. I was under the impression that a simple press and release of the button would switch/toggle the mode for you... but it is really a press and hold for a "temporary" switch while you are holding it... but upon release it goes right back to where it was before.

Not quite what I was expecting but I could see where it would be useful for some. It would be more usefull (for me) if it were a simple press and release of the button for a quick permanent switch of the mode until you press and released it again to switch back or changed it in settings.

Still cool though.
--
-Brock
A few of my images: http://www.brockbarnes.com

--
http://www.flickr.com/photos/39169343@N04/

 

[reginalddwight]

This may have been covered previously, so my apologies for any repetition. Does use of the back AF-On button to lock focus and recompose throw off the metering, particularly with spot metering or even center-weighted average for that matter? Many thanks.

 

[Dr. Leonard]

I use the C1-C3 function button on the click wheel to set one shot or AI Servo.
--
I am not responsible for my opinions.

 

[Loren Charif]

Actually, it's not new; it's been around since the early xxD's...not sure if it was 10D or 20D, but it's been there for as long as I can remember.

Loren

You really don't have to. There is a new setting between On Shot and AI Servo called AI Focus. The camera will swich for you if it detects that the subject is moving.
--
Todd Haehn

--
http://www.pbase.com/lorenbc/
http://www.photosig.com/viewuser.php?id=4994

 

[hdngo1]

Can some one please confirm whether this can be done on the 40D and how or is it only for the new 7D? Thanks

I see what it is doing now when you assign the ONE SHOT AI SERVO to the depth of field preview button. I was under the impression that a simple press and release of the button would switch/toggle the mode for you... but it is really a press and hold for a "temporary" switch while you are holding it... but upon release it goes right back to where it was before.

Not quite what I was expecting but I could see where it would be useful for some. It would be more usefull (for me) if it were a simple press and release of the button for a quick permanent switch of the mode until you press and released it again to switch back or changed it in settings.

Still cool though.
--
-Brock
A few of my images: http://www.brockbarnes.com

 

[Zeee]

There we go. I like that idea.

 

[Zeee]

Yea... if someone could explain how to set it (7d) up to where the shutter release button doesn't focus on the half press... and the AF-ON button does focusing then it would be greatly appreciated. I tried deciphering that section in the manual but it is a little confusing for me also. And I didn't see anywhere how to setup the preview button to toggle between the two focusing modes. If that could be explained on how to setup (or if someone could point in the manual where it talks about it and maybe decipher it) that would be awesome.

Thanks.

--
-Brock
A few of my images: http://www.brockbarnes.com

That part of the manual is very poorly written

 

[Zeee]

"would I assign the One-Shot AI SERVO to the depth of field preview"

Yes

"and then assign AE lock to the shutter release button"

No, assign Metering start. The default is AF start and Metering start.

--
http://www.flickr.com/photos/39169343@N04/

But then you have to hold the DOF button.

 

[Zeee]

I also decided not to use it, as it feels awkward to shoot while holding the button.

I see what it is doing now when you assign the ONE SHOT AI SERVO to the depth of field preview button. I was under the impression that a simple press and release of the button would switch/toggle the mode for you... but it is really a press and hold for a "temporary" switch while you are holding it... but upon release it goes right back to where it was before.

Not quite what I was expecting but I could see where it would be useful for some. It would be more usefull (for me) if it were a simple press and release of the button for a quick permanent switch of the mode until you press and released it again to switch back or changed it in settings.

Still cool though.
--
-Brock
A few of my images: http://www.brockbarnes.com

--
http://www.flickr.com/photos/39169343@N04/

I found that as well.

 

[hdngo1]

Anyone? I would like to know how to do it. Thanks

Can some one please confirm whether this can be done on the 40D and how or is it only for the new 7D? Thanks

I see what it is doing now when you assign the ONE SHOT AI SERVO to the depth of field preview button. I was under the impression that a simple press and release of the button would switch/toggle the mode for you... but it is really a press and hold for a "temporary" switch while you are holding it... but upon release it goes right back to where it was before.

Not quite what I was expecting but I could see where it would be useful for some. It would be more usefull (for me) if it were a simple press and release of the button for a quick permanent switch of the mode until you press and released it again to switch back or changed it in settings.

Still cool though.
--
-Brock
A few of my images: http://www.brockbarnes.com

 

[DavZell]

IF your in AV or TV mode and use exposure lock, hold the * button and turn the wheel near the shutter, and it will change the shutter speed and aperture, just like in P mode, when you do program shift.

This is handy if you want to make quick change on the fly

I'm not sure I see any difference from just spinning that wheel without holding dow the * button. Can you expain?

Thanks,
D.

 

[RedFox88]

I think I am correct to say this was introduced by canon many many moons ago after a lot of consultation with sport pro shooters.

Didn't the 10D have an AF-on type button and then the 20D had it removed? Sort of like Canon though it was too high end a feature at the time to sell for $1600. My 1v has it.l

 

[Steve Balcombe]

... of back-button focusing is that you can use it for effectively simultaneous AF mode and MF mode, but only with Ring USM lenses (i.e. all the L's and a few others) with their 'full-time manual' capability. Simply move AF to the back button and leave the lens in AF mode. If you don't press the back button you have normal manual focus. But when you want AF it's always available without having to fiddle with any switches.

 

[tko]

You can not, of course, actually switching between AI servo and one shot using the AF ON button, so this type of statement confused me at first. What you are doing is simulating one shot in AI servo by turning focus on and off. Practically, it's the same thing, except you don't get the AF confirmation light/beep, plus the focus acquire is really done when you release the AF ON button (as opposed to pressing the shutter). It's a great tip though.

 

[carlk]

Just assign the meter start to shutter half release. It will meter just like before when both AF and metering were assigned to it.

 

[Juan I Perez]

Hi. That is an excellent use of the AF-ON button. I did used it like that with my 40D.

Now since I switched to the 7D I have gone back to the focus, meter and shoot with the main shutter. I still use the AF-ON button...to STOP autofocus. I find this setup more ergonomic...as long as you dont have the problem you explaing for finding the mid press point on the main shutter!

And to switch on the fly between one shot and all servo I have that set on DOF button.
--
Juan

 

[samWebster123]

it's great to setup a custom setting for this in say C1 for those of us shooting in low light or astrophotography.

This way you're not forgetting to turn AF off on the focus and re-compose shots.

 

[Steve Balcombe]

it's great to setup a custom setting for this in say C1 for those of us shooting in low light or astrophotography.

This way you're not forgetting to turn AF off on the focus and re-compose shots.

I no longer use C1/2/3.

Let's say I've set up C1 for a default shooting style I happen to like - say Av mode, f/8, ISO 100 etc. At the start of a session I switch to C1 and begin shooting, but light levels are a bit low so I adjust the ISO setting to 400. During a short pause in shooting, the camera powers down - although I don't even notice this when I pick up the camera because it wakes up instantaneously. But the ISO speed adjustment has been discarded .

That's no good to me, I don't want the camera changing anything without my explicit say-so.

Actually I must check whether my 7D behaves the same way, but I expect it does.

 

[jayboo]

I have just read through this thread and learnt so much - the manual really is no good at explaining the whole af-on button stuff - I too am waiting for a better manual for the 7D - "Dummies" is going to be the one for me I feel. However - I think by following this thread through a few more times it will all be clearer.
--
Jayboo