7D auto focus

[RKC]

I believe that you can select an amount of focus point ?

Say you want a bird in flight, you are using centre point, you can add some extra focus points around that point, anything that falls into that cluster the camera will attempt to focus, am I understanding that to be correct?

If this is the case how accurate is it? for example if you are targeting the eye but one of these other points picked up the wing as it would be nearest the camera that would then become the focus point :shrug:

Bob

 

[artyman]

Using the assist points helps with BIF but my technique is nowhere near good enough to keep any focus point on the eye of a BIF, if you can I stand in awe.

 

[cornishboy]

Couldnt you just change the f stop.?

 

[scottthehat]

Couldnt you just change the f stop.?

 

[OneTen]

The expanded AF point works by always trying to focus with the single selected point first, but if this fails it will then try with the four surrounding points (above, below, left and right) if they are available. If the selected point is on the edge of the focussing points then only two or three expanded points are used depending on the position.

I use this with an aperture of f/8 if possible for birds in flight to try and keep the eye in focus.

There is also a Zone AF area which uses nine AF points but focusses on whichever part of the subject is nearest to camera. This zone can be moved around to (I think) 5 different predetermined positions. I don't use this option.

 

[dinners]

Changing the f stop (I know what you mean) sort of helps in that if you slightly miss your target (shoulder instead of eye etc) the depth of focus will be more forgiving with a smaller aperture.

I use expanded AF points for birds in flight as sometimes you miss altogether with centre point and end up with focus on something far behind.

 

[Oggy]

Using the assist points helps with BIF but my technique is nowhere near good enough to keep any focus point on the eye of a BIF, if you can I stand in awe.

Agreed all points.

 

[RKC]

Using the assist points helps with BIF but my technique is nowhere near good enough to keep any focus point on the eye of a BIF, if you can I stand in awe.

Do not stand in awe Ken, although when I have tried bif I do aim for the eye, probably where I go wrong as its such a small target

 

[RKC]

Couldnt you just change the f stop.?

I do normally shoot around F8

The expanded AF point works by always trying to focus with the single selected point first, but if this fails it will then try with the four surrounding points (above, below, left and right) if they are available. If the selected point is on the edge of the focussing points then only two or three expanded points are used depending on the position.

I use this with an aperture of f/8 if possible for birds in flight to try and keep the eye in focus.

There is also a Zone AF area which uses nine AF points but focusses on whichever part of the subject is nearest to camera. This zone can be moved around to (I think) 5 different predetermined positions. I don't use this option.

thank you for that explanation Richard, I now have a better understanding

Changing the f stop (I know what you mean) sort of helps in that if you slightly miss your target (shoulder instead of eye etc) the depth of focus will be more forgiving with a smaller aperture.

I use expanded AF points for birds in flight as sometimes you miss altogether with centre point and end up with focus on something far behind.

Missing focus is I think my biggest problem

Thanks everyone for contributions

I have heard several comments about the AF on the 7D, so I just wanted to understand a tad more about the system, I had no idea how the expanded view worked or even what it was called