I need some help with the difference between focus modes.

Hi there,

I was wondering what the difference between the 3 focus modes. One shot, AI focus and AI servo.

I have read the manual but I do not understand what they do.
Any help would be great.

Regards Darren

I will give it a try at explaining.

- One shot mode basically focuses the lens and once it achieves focus it stays there until you completely release the shutter button and then press it again. It is best for stationary subjects. If your subject moves (or you do) you will need to release and press the shutter at least half way to achieve correct focus. It is the most accurate mode of auto-focus.

- AI Servo mode is mainly aimed at moving targets and once it has the subject in focus your focus will change with the target (up to a point) until you release the shutter. It will try to follow the target in other words. The catch is if it focuses on the wrong subject you will need to release and re-press the shutter for it to try again. Other then it tends to be not quite as accurate as one shot mode, it is way more flexable for most applications.

- All AI focus mode does is the equivilant of letting the camera choose the mode the camera should be in between One Shot and AI Servo. It first presumes the subject is stationary, but switches to AI servo mode if it detects that the subject is moving.
The reason to use this mode is if you don't want to think about your camera. The reason to not use this mode is it will take a bit longer to track a subject then selecting AI servo to begin with, which means you may miss your subject. Also you may have some problems keeping correct focus on a stationary subject if handholding and you are swaying as it will switch to AI Servo sometimes thinking the subject is moving.

Or short form:
Use One Shot for stationary subjects,
Use AI Servo for moving subjects,
and Use AI Focus when you can't make up your mind.

And finally use Manual focus when you don't trust the camera's auto-focus.

cool thanks,

manual focus is no worries, and one shot i had...the others were blurry. Thanks

Regards Darren