« on: February 07, 2014, 01:26:17 AM »
@Cervantes: Did you ever try to shoot birds or any kind of sport with AF Expansion mode including 4 or 8 additional surrounding points? I never know which mode is better - Zone or AF Expansion. Can you tell why AF Expension mode would not be appropriate for birds or sports?
Otherwise, very good and informative article!
No, I never use AF Expansion mode for the following reasons:
- AF expansion is basically single point AF where the camera uses the surrounding points only if the center point can't achieve AF (this is basically what East Wind Photography said).
- AF expansion covers an area that is too small for my taste - In fact I would love it if I could select an AF mode that uses all 20 points on the left / right side of the frame. Or even better if I could define my own zones via a custom function!
- When you move the expanded AF point the movement happens point by point (ten clicks from the leftmost AF point to the rightmost AF point) - thus very slowly. Zone immediately switches to the next zone (two clicks from the leftmost Zone to the rightmost Zone).
- There is an option in the AF menu where you can turn all the modes off that you don't need. For my action setting C1 I turned off everything except Zone AF, 61pt AF and single point AF (which can't be turned off unfortunately - otherwise I would). It is much faster to select what you need when you don't have to scroll through everything.
Thus, if one is tracking a bird with AF Point Expansion in AI Servo mode, this would be quite similar to Zone AF. And try to have the main AF point near the eye, let's say. Or not?
Probably true. But keeping in mind all the disadvantages above - why don't you simply use Zone AF which will get the job done for sure?
Thanks for the input by the way!