al servo or al focus mode useful for weddings?

in the past my 20d has been in "al focus" mode (today i switched

to "one shot") which is suppose to detect if your subject is moving

or not and function in the appropriate mode ("al servo" or "one

shot"). i sometimes get shots where my subject is not as sharp as

the background and I know i focused on my subject. however, i might

have focused and recomposed and also realized after going through my

manual again that "focus and recompose" only works in "one shot"

mode. so, my question is does anyone prefer "al focus" or "al servo"

mode and use it at weddings? for possibly the procession and

recession where people are moving towards you? thanks.

I will sometimes use al servo on my 1dmkII because it seems to hunt sometimes for focus otherwise. I also make sure I use the center focus only when I do that so I make sure I am focusing on the subject not the background.

AI focus will slow the focus down as it has more thinking to do. Using one shot with the center focus point will provide the fastest possible focus for that reason, most sensitive point, least thinking.

 

I used to use AI Servo more, for processions, dancing etc but that was in the days of shooting with my Elan II's which had it on the dial so I could switch without taking my eye from the viewfinder. With the modern crop of cameras where it takes a button press (two with the 1 series), twiddle dial in the correct direction and half press shutter release, I find it faster, easier and ultimately safer (not as confusing or to find out I shot the entire ceremony in AI Servo with doing focus recompose by mistake!) just to zone focus or my own trick which is to focus as they move towards and then pull the zoom back a bit to provide more DOF and proper composition as they walk further towards, all within a 1/2 second.

As you found out, AI Focus mode and focus/recompose don't go together. Any slight movement of the camera (even inadvertent--even if you aren't focus/recomposing) causes the camera to think the subject is moving and it will merrily focus on "whatever" in the background. I never use that mode.

 

AI Servo I use only in good light. Otherwise, it is too slow. So processionals/recessionals are zone/pre focus only. Some other parts are zone/pre focus as well--such as some dancing shots in low reception light. Lately, I've tried Marc Williams' "focus on the shutter button, snap in one motion" technique, which works well if your focus is already close. Otherwise, there is a lag which can frustrate you.

Delanza,

 

I use AI Servo only for procession and recession and one shot for everything else. I've never had an out-of-focus problem.

 

For AI servo to work properly you must give camera time to calculate the predictive focus. I manually select camera's focus point that gives me the framing I want and will cover subject's face, then as subject starts moving press shutter half-way and hold for a 2~3 count - focus point must remain of face during this time - then when you get shot you want press shutter completely. Always in focus with this method. I do not use the center focus point, but as stated, it is more sensitive. On 1 series bodies and 2.8 lenses I don't have problems using any FP.

 

On your 20D you may have to use the center focus point, especially if you are using a slow lens. Also, be aware that the red sq. of the FP is not the actual size of the focus censor. The censor is larger and that can sometimes cause the 20D to focus on the background, especially if it is high contrast to the main subject.

 

Cliff

Sorry, it's too early and not enough caffeine yet.

 

Should read - focus point should remain ON face during this time -

No.

 

One shot and for the pro/recessionals, I pre focus on a pew or some such and wait for them to step into the 'range' based on the F-stop chosen (usually about 5.6).

I have also located the focusing button.. on the rear of the camera --not the shutter release--helps me considerably.

AI Servo almost all the time.

 

AI Focus seems to be for when you can't make up your mind and want the camera to decide. I don't see any benefit to one shot. When I want the camera to stop focusing, I'll release the focus button. I use the custom function to put it on the * button on the back. That way, the shutter release is *just* for metering and taking the picture.

 

Another advantage to AI servo is that you don't get that red light from the flash in dim light.

 

 

Eric

Nadine is right. With the "push the shutter button all the way" method you have to have the

lens reasonably close to the distance you'll be shooting at so the lag is eliminated. So I focus

on a few guests being seated and leave it there. Then, once you shoot the first one leave the

focus ring alone (easy to say, hard to do : -)

 

The most fool proof way is to shoot stopped down on Manual focus and prefocus at a given

distance .... so when the procession subject enters the zone you shoot. You can also back-

track at the same pace as the subjects and keep shooting if you want. You have to keep your

mitts off the focus ring for this technique also.

I actually have more trouble keeping my finger off the focus button and confusing myself when I've set the focus to manual for zone focus. Still adjusting to using the on/off focus switch on the lens. Wedding photography can be scary sometimes... When you are so used to a procedure, you can flip buttons and switches when unconscious--then you change something and the whole thing needs to be relearned.

Lots of good feedback here. Thanks everyone. I'll experiment with my wife and kids this week before my wedding this Saturday.

 

Delanza/Chicago,IL