This is something I’ve been exploring lately as I really wasn’t sure what the differences were. Even with all the info that is out there on the subject I’m still a little confused as to where someone would actually use the AI FOCUS mode. I have to admit that I had not (up until recently) experimented with any mode other than ONE SHOT.

Shooting sports in ONE SHOT mode therefore becomes a little tricky and you really have to be quick when it comes to refocusing the subject as they are moving (ie. pressing the shutter half down). Obviously this becomes tedious, but the payoff is a fairly reliable chance of getting an in focus moment, dependant of course on many other factors as well.

The problem starts to come into play when you are shooting wide open (ie. 2.8 or lower) and now your shallow depth of field makes prefocussing a bit of an issue especially if your subject moves towards or away from you the instant you decide to capture the moment. The best solution from all the information that I’ve scoured from the internet is that AI SERVO is the best bet. One caviet, this mode will only use the centre focus point for focusing…. which I figured is acceptable in a fast moving situation, but leaves very little room for creative composing during moments of inactivety that you may want to catch. I mean who wants to have to  switch back to ONE SHOT mode and then back to AI SERVO mode constantly.

And then I found there is a solution to this. A fairly well known one too! I wouldn’t exactly call it a secret because it is published in the canon manual, but really who reads that crap anyway, kidding. So what I found is that if you venture into the menu system and down to the ‘custom functions’ area (C.fn), you go to the 4th selection and you choose the first option (ie. C.fn 4-1), you’re camera will now focus by means of the * button on the back of your camera. The exposure setting is taken care of by the shutter release button being held down half way but will NOT focus any longer.

Initially I thought, ya, so what. Don’t see the advantage…. well, here is where this really works well. Say I’m shooting soccer or any other situation where there is a lot of movement, and typically you’ll find a lot of times there isn’t a lot of action, but when the action is there you need to be ready for it.

Now using this technique, that is being in AI SERVO mode and also having your ‘custom function’ number 4 set with option 1, you’ll be using the * button to focus on the action as it happens, you can keep shooting as the action starts moving toward or away from you confident that you will have more keepers than deleters. 

If you see something that’s happening statically while there is no play going on but you know you want to compose your image with the focal point placed off centre, you simply lock your subject with the centre focus point and the * button pushed down, release the * button and now you can recompose however you want knowing that your subject will be in focus (providing it or they don’t in any way of course).

So the jury is still out, but I’m liking it. My wife on the other hand may not like it and I suspect I’ll get a call on the cell phone the day she goes to use it and finds that it won’t focus. I’ll cross that bridge when I come to it.

Go ahead and give it a try, you might like what you find. Rob.

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