AI Servo and AI Focus in Canon

[spade]

hello, the manufecturer (Canon) claims that the "AI Focus" option switches automatically between "one shot" and "AI Servo". i've heard Pro's and Con's from some people. Does anyone have real experience with this? is it reliable?

[Geoff F]

For me, Zvika, it all depends on the actual scene.

I always find normal One Shot to be the best option. But sometimes this doesn't suit the conditions.

Moving targets, for example flying birds, are a typical example where AI Servo can achieve and hold sharp focus where 'normal' settings would fail. Providing you can pan your camera to keep a focus point on the target.

But servo auto focus can 'hunt' around while searching and holding sharp focus, so I don't like using it where the focus depth is shallow, such as macro photographs.

AI Focus is supposed to be the best of all options but I tend to think there is a risk that in attempting to suit all conditions it 'pleases nobody'.

However, I have sometimes accidentally left my camera on AI Focus and shot all day without noticing any differences between that and One Shot.

[William W]

Does anyone have real experience with this? [AI Servo]

Yes.

is it reliable?

Yes, if one understands the operations; functionality and limitations.

Generally for MOVING Subjects which will occasional stop and/or change direction - AND - if the Subject is kept on the AF Focus Point, AI Servo Focus is very good.

I will always use the centre AF point when using AI Servo.

Typical applications for me are: field sports, such as Hockey, Football, where the movement of the Subject is NEITHER predetermined nor rhythmic (as opposed to Competition Swimming, which is both predetermined and rhythmic ).

Also understand that the AF will work on CONTRAST differences and does not reckon on exactly the area of the red square in your viewfinder.

"AI Servo" is likely to hunt badly if both the Subject and the Camera are static - I have lots of tests showig that

What Camera(s) do you have?

WW

[spade]

thanks. I was using the 40D for the last 3 years and recently upgraded to the 7D.

[RustBeltRaw]

Your initial post is correct, Zvika. However, I tend to avoid AI Focus and use either One Shot or AI Servo modes, since I want to know exactly what the camera's going to do when I half-press the shutter. I shoot a lot of action, where AI Servo is at its best. However, since I'm also shooting with the center AF point most of the time, it's possible to point the camera into a gap between players, and hit the shutter while it's trying to refocus on the background. Irritating, but using One Shot focus with a moving subject is nigh-impossible.

One Shot's my usual mode for landscape, architecture, urban exploration, portraiture, and some long-exposure work. I usually select one of my camera's 9 autofocus points instead of using the intelligent mode. It always seems to land somewhere other than where I want the focus.

[rpcrowe]

thanks. I was using the 40D for the last 3 years and recently upgraded to the 7D.

I shoot with both the 40D and the 7D so, I am pretty well experienced with both cameras.

I tend to use either the single shot focus or the AI Servo. I don't use AI Focus.

With either the 40D or 7D (and to a lesser extent with the 50D and 60D) a photographer can have both the Single shot and AI servo registered on one of the User Selected Modes. It is very easy to switch between these modes with a single turn of the mode dial.

The 7D has remarkable auto focus, even in its default modes. However, you can increase the (IMO) already mind-boggling A/F capabilities of the 7D by using some of the focus modifications available.

Again, that is where the User Selected Modes can come in handy. You can set up your camera for various auto focus methods and modifications. I don't know why Canon reduced the number of User Selected Modes from 3 in the 40D, to 2 in the 50D and further reduced the number to a single user selected mode in the 60D. I am just glad that they returned to three User Selected Modes in the 7D. I use mine all the time and would recommend anyone to investigate User Selected Modes if they are fortunate enough to have this capability in their camera.

http://cpn.canon-europe.com/content/...s_explained.do

http://www.learn.usa.canon.com/resou..._article.shtml

http://forums.dpreview.com/forums/post/34928912

Lots of YouTube tutorials on 7D A/F located at:
https://www.youtube.com/results?sear....1.tDfLbF0Aw_A

[Donald]

There's a theme to the posts above ... and that seems to be that no-one really uses AI Focus. I'd add my name to that list (I'm a 40D user). I've never used it.

What I'd really endorse is Richard's comment re the User Selected Modes. I have the three on my 40D all set up slightly differently and very, very rarely do I use anything other than the C1, C2 or C3 on the top dial. As Richard says, flicking between them is so easy if and when you are even in situation, fro example, when you want to quickly move from 'One-shot' to AI Servo. For me that's just a case of flicking from C1 to C3 and I don't even have to take my eye from the viewfinder.

[RustBeltRaw]

I definitely second Richard and Donald's call for more user-selected modes. I use a 60D, and I'm frequently in situations where I need to swap settings fast. Most notably, going from long-exposure work with fire dancers to quick candids between their sets. At the moment, I have to change white balance, shutter speed, ISO, aperture, flash triggering mode, flash compensation, and remote settings in about two seconds. I have it down to about twelve, but that's still a long way off. That said, do existing user-selected modes remember flash settings?

[rpcrowe]

I definitely second Richard and Donald's call for more user-selected modes. I use a 60D, and I'm frequently in situations where I need to swap settings fast. Most notably, going from long-exposure work with fire dancers to quick candids between their sets. At the moment, I have to change white balance, shutter speed, ISO, aperture, flash triggering mode, flash compensation, and remote settings in about two seconds. I have it down to about twelve, but that's still a long way off. That said, do existing user-selected modes remember flash settings?

Page 263 of your 60D manual indicates that Flash firing, shutter sync, FEC, E-TTL II metering and wireless function can be registered to one camera user setting.

Obviously, the Canon Gods do not consider the Camera User Settings very imortant. I have never seen them listed as important bells and whistles of the cameras... They are very important to me.

[RustBeltRaw]

Page 263 of your 60D manual indicates that Flash firing, shutter sync, FEC, E-TTL II metering and wireless function can be registered to one camera user setting.

Hm. I definitely need to go back to the manual, because I've tried setting different flash and exposure parameters in C, only to have them revert when I switch modes. I always RTFM, but I must be missing something.