AF modes with the 400D

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michaelho

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Getting a bit confused with the AI servo mode on the 400D.
Tell if I'm right, or wrong, here:

One Shot:
The red dots show which bit of the picture is in focus and locks the focus to these points/ point.

AI Focus:
Switches between one shot and AI servo when camera deems necessary.

AI Servo:
Initially puts the focus on the middle focus point and then track that specific point and keeps it in focus even if you/subject moves.

Is this right?

What I'm confused about is when in AI Servo mode, say if I'm taking a portrait, if I initially place the eye in the middle focus point so that the camera focuses on it and then recompose so that now the upper chest is covered by the middle focus point, what is in focus now? The eye still or the chest?

Hope you kind people can help me out!

Michael.
 
Firstly Michael, you need to set your custom functions to allow the star button at the back of your camera to be your focus button (it should be custom function 04 "Shutter/AE lock button" - set it to option 3) - a lot of people don't use this but it is by far the best piece of advice I have received to date regarding my camera - if you choose to do this then the advice below will work perfectly, if not then it wont (no, really :lol:)

You are basically correct in your assumptions about the focus modes - In the example that you state, the camera would shift focus to the chest due to the camera thinking that it needs to keep tracking motion (that isn't really there)

My camera hardly ever leaves Servo (AI focus is a waste of time imho) - You can change your autofocus point though - try setting it to one of the further points & using this point to focus on the eyes, release the focus button & take the shot using the usual shutter button. As your camera is on servo mode, the camera will not try to refocus unless you press the focus button again.

Hope this helps (but if I've confused the hell out of you then feel free to PM me & I'll walk you through setting up your camera) :thumbs:
 
Wookie, I did read that post a while ago and although it was very useful I'm still confused whether it would track the eye or move focus on to the chest (with the example I gave above)?

moomike I will pm you later today regarding setting up the camera!

Off to Uni now.
 
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