Guide to setting up Al Servo?

[Paul Kammen]

Hi all,

Soon purchasing a 70D, and wondering if anyone could give me any resources for setting up autofocusing. On my old system, it was just simply C-AF and that's it. Pleased that Canon will allow me more options, but if there are any resources out there for tracking birds in flight, that would be very helpful.

Thanks so much,
Paul

[Diane Miller]

Most people find back button focus excellent for birds in flight (and everything else). How to set it up will be in the manual, along with setting AI Servo. You can download the manual ahead of your purchase.

Do an internet search for back button focus on Canon cameras and you'll get good info.

[BobbyPerkins]

To each thier own on AF preference, For tracking birds in flight back button focus is not my preference. I believe most those who specialize in birds in flight don't use back button AF either. But, is entirely a matter of preference. As far as "resources out there for tracking birds in flight" I highly recommend Jim Neiger's book Flight Plan. He's also posted many tutorials specificly for tracking birds in flight for example the "bump-focus" technique as well as camera settings for BIF here in the forums and elsewhere.

[Diane Miller]

The term back button focus isn't really the complete description and I wasn't clear that what I meant it is back button focus with AF mode set to AI Servo, and focus not activated by the shutter button. That way as long as you hold down the back button you are tracking the moving subject in terms of distance change. Would be the same as holding the focus button halfway down with AI Servo set, but you don't have to be quite so careful to keep it halfway down. Then when you're ready to shoot just hit the shutter button while still holding the back button.

One advantage is if something else enters the frame or intervenes you can momentarily let go of the button and you are in MF until you have the subject re-framed on a focus sensor.

I was under the impression this is a very widely used method. Would be happy to learn if that's not correct. I haven't read Jim's book, but bumping the focus is used with back button AI Servo as well, if focus seems to be drifting.

Another advantage is that you can switch instantly from AF to MF, by achieving focus then letting go of the button, which allows convenient re-framing while holding a set focus.

Would love to hear what others do.

[BobbyPerkins]

I completly understood what you meant by back-button focusing and it is a very widely used method.


For switching from "AF to MF" if you mean AI-servo to One-shot like feature by locking focus and recomposing (when you let off the back button), Instead (by preference), I have set the *Star button to AF Lock (on the 7D it's AF OFF). This gives me the "One-shot" feature by pressing and holding the * button to lock focus & recompose images of static subjects while remaining in AI-servo mode. I just prefer the shutter button for focusing, metering and shooting all in one sweep, especially when tracking birds in flight.

[Doug Brown]

Have a look at this 7D setup guide (http://www.deepgreenphotography.com/2009/12/setting-up-your-new-canon-7d/) I wrote when the camera first came out.

[Jim Neiger]

The term back button focus isn't really the complete description and I wasn't clear that what I meant it is back button focus with AF mode set to AI Servo, and focus not activated by the shutter button. That way as long as you hold down the back button you are tracking the moving subject in terms of distance change. Would be the same as holding the focus button halfway down with AI Servo set, but you don't have to be quite so careful to keep it halfway down. Then when you're ready to shoot just hit the shutter button while still holding the back button.

One advantage is if something else enters the frame or intervenes you can momentarily let go of the button and you are in MF until you have the subject re-framed on a focus sensor.

I was under the impression this is a very widely used method. Would be happy to learn if that's not correct. I haven't read Jim's book, but bumping the focus is used with back button AI Servo as well, if focus seems to be drifting.

Another advantage is that you can switch instantly from AF to MF, by achieving focus then letting go of the button, which allows convenient re-framing while holding a set focus.

Would love to hear what others do.

I think it is really a matter of personal preference, but for me there are 5 reasons to use the shutter button to focus instead of using a button on the back of the camera to focus.

1. My index finger is more coordinated than my thumb. This allows me to bump the focus with more finese than the back button.

2. The shutter button is larger and has more give than the back buttons. It is easier to feel what you are doing particularly in cold weather.

3. I can focus and shoot by following thru with one motion on the shutter button as opposed to coordinating my finger and thumb to focus and shoot.

4. I can adjust exposure during a burst of shutter releases without pausing. This is not possible with back button focus.

5. When shooting in very cold weather I need only one small hole in the glove over my index finger. If I used a back button to focus, I would need a thumb hole as well.

[arash_hazeghi]

I also use the shutter button for the same reasons as Jim mentioned. But it's a personal choice, some people are more comfortable with back button...but shutter works just as well.

[Mike Milicia]

It's definitely a personal choice and it's good to be familiar with both methods but I also prefer to use the shutter button for all of the reasons given above plus a couple more. The first is that I like having my thumb free for changing the focus point without having to interrupt AF. The second is that when working low from a prone position with a ground pod, I sometimes find it more comfortable and more stable to utilize the shutter button on the vertical grip even when shooting horizontal, i.e. using the shutter button on the bottom of the camera. In this circumstance, it is fairly awkward to also use back button focus.

[Jonathan Ashton]

I have repeatedly tried rear button AF on my cameras, it takes some getting used to. In the end I come back to using the shutter button for AF and I use the Rear Focus button to stop focus. I closely identify with all the preceding reasons for doing this.

[BobbyPerkins]

For all the same reasons above & more I use the shutter button for AF.
Another reason (as Mike Milicia stated) is I use the joystick alot to quickly and easily move the AF point where I want it with out taking my eye off the viewfinder while focusing. That AF point may vary as I'm shooting. Using the back-button AF that wouldn't be possible.